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Ifs 101

ScottRS said:
Set 20 tapered roller bearings and seals, it was just a teeny tiny semifloat 9" rear end. I'll dig around in my shelves and decide if I want to take pictures, the idea is a lot prettier than the "learning to weld on borrowed equipment" fabwork.
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I'm interested in pics, even with booger welds.
 
YotaAtieToo said:
I've thought about doing something like this for more of an oem upgrade, so stubby as possible on one side, with a short tube on the other. Say replacing a stock diff in a 3rd gen 4runner for a "mid travel" type setup. The rcv kit is pretty strong, but the 7.5" center section isn't :laughing: I feel like center mount for longer CV's isn't really a huge advantage when your a arms are mounted outside the frame. Having done that, would you agree?

It may be better at that point to just buy the aftermarket narrow diff and then make a double flanged shaft with some type of support bearing. But as we've discussed, those are damn pricey.
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At 18.5"-ish flange to flange, center mounting the diff didn't gain much halfshaft length over the Toyota 7.5 anyway. Obviously the 9" gained a lot of strength over the 7.5, but the lateral pinion offset made for a wonky front driveshaft situation. Had I started with the dutchman housing I could've offset the diff enough to make the driveshaft slightly better, but I think the working halfshaft length difference would've added up to near no benefit anyway, the shafts were close enough to right length but the joints that I could get at the time couldn't survive the torque and angle combo I could generate.

I'm not sure where "mid travel" vs "long travel" vs whatever is any more. Mine could do 18" but it broke a lot of stuff if I did that. Practical limit was about 14". The big thing was the extremes of travel compounded with steering, I could break outer CV's faster than I could change them prior to limiting it a bit.

Some time later Diamond Axle built a toy 8" ifs front that I believe is 30sp hub to hub under a 2000ish 4runner. That seems to me like about the best middle ground of strength and packaging and cost, but I don't think it went anywhere significant commercially. Good bit of RCV in it IIRC.
 
ScottRS said:
At 18.5"-ish flange to flange, center mounting the diff didn't gain much halfshaft length over the Toyota 7.5 anyway. Obviously the 9" gained a lot of strength over the 7.5, but the lateral pinion offset made for a wonky front driveshaft situation. Had I started with the dutchman housing I could've offset the diff enough to make the driveshaft slightly better, but I think the working halfshaft length difference would've added up to near no benefit anyway, the shafts were close enough to right length but the joints that I could get at the time couldn't survive the torque and angle combo I could generate.

I'm not sure where "mid travel" vs "long travel" vs whatever is any more. Mine could do 18" but it broke a lot of stuff if I did that. Practical limit was about 14". The big thing was the extremes of travel compounded with steering, I could break outer CV's faster than I could change them prior to limiting it a bit.

Some time later Diamond Axle built a toy 8" ifs front that I believe is 30sp hub to hub under a 2000ish 4runner. That seems to me like about the best middle ground of strength and packaging and cost, but I don't think it went anywhere significant commercially. Good bit of RCV in it IIRC.
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Gotcha, I guess I haven't had a tape on a normal Toyota center, but now that you say that, I'm guessing it's not much more than 18". Realistically, just using a newer Toyota 8" clamshell ifs diff is the best bet for an up grade, but not as cool as a 9" center :laughing: I just figured if you're going through all the work to retrofit a new diff, may as well go all the way.
 
Just some info for those guys (and me) who were wanting to possibly base a build around the Chevy 3500 CV shafts. I called RCV and got some more info about their replacement shafts for the Chevy IFS:
  • The inboard joint on their shaft is NOT a tripod joint like the stock joint is. It is their version of the 934 plunging joint and 33-spline where the shaft goes into it. It has about 1.5" of available plunge.
    • The reason the shaft is 33-splines at this end is because that is the stock spline profile of a 934 joint. So theoretically if you were in a pinch and needed a joint to fit your shaft, you could find one at a parts store if you know the correct application.
    • They can make a 35-spline plunging joint here if you wish.
    • 35* max working angle.
  • The outboard joint is the same joint used on the Chevy SFA shafts. It is 35-spline where the shaft goes into it. I asked if it was a 934/935 joint for strength comparison and they said it was "comparable" but not a 934. It is their "spherical version" of a 934 joint, which allows them to use their plastic boot to seal it. I don't know exactly what that means, it's just what they told me.
    • 40* max working angle.
  • They will not make a custom-length shaft to fit the stock Chevy joints. So this rules out trying to be cheap by starting with those.
    • It wouldn't really matter even if they would since, presumably, you would eventually be replacing it with their shaft, which would then require a different shaft to match their inner joint, that is different than the stock Chevy inner joint. So to start with stock Chevy joints with a custom length shaft, you'd be paying for a custom shaft that would be trash the instant you upgraded joints.
  • Even though different in design, both inner and outer joints are similar in strength. The weak link in the shaft is the shaft itself.
After learning all of this, at least if you're set on RCV products, there does not seem to be a way around the initial $2500+ hit of custom shafts.

To start on a budget-build with the intent of upgrading later one would have to know stock applications of 934 joints with a list of shaft lengths and design to fit two of them. But this would leave you with a spline limitation at the UB that would likely come back to bite you.

So basically no way around aftermarket for your first set of shafts.
 
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patooyee said:
They will not make a custom-length shaft to fit the stock Chevy joints. So this rules out trying to be cheap by starting with those.
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I don't see that being an issue. Tons of places will cut and roll splines on any axle shaft you want to send them. If you give them a shaft to copy they're even happier.
 
patooyee said:
Just some info for those guys (and me) who were wanting to possibly base a build around the Chevy 3500 CV shafts. I called RCV and got some more info about their replacement shafts for the Chevy IFS:
  • The inboard joint on their shaft is NOT a tripod joint like the stock joint is. It is their version of the 934 plunging joint and 33-spline where the shaft goes into it. It has about 1.5" of available plunge.
    • The reason the shaft is 33-splines at this end is because that is the stock spline profile of a 934 joint. So theoretically if you were in a pinch and needed a joint to fit your shaft, you could find one at a parts store if you know the correct application.
    • They can make a 35-spline plunging joint here if you wish.
    • 35* max working angle.
  • The outboard joint is the same joint used on the Chevy SFA shafts. It is 35-spline where the shaft goes into it. I asked if it was a 934/935 joint for strength comparison and they said it was "comparable" but not a 934. It is their "spherical version" of a 934 joint, which allows them to use their plastic boot to seal it. I don't know exactly what that means, it's just what they told me.
    • 40* max working angle.
  • They will not make a custom-length shaft to fit the stock Chevy joints. So this rules out trying to be cheap by starting with those.
    • It wouldn't really matter even if they would since, presumably, you would eventually be replacing it with their shaft, which would then require a different shaft to match their inner joint, that is different than the stock Chevy inner joint. So to start with stock Chevy joints with a custom length shaft, you'd be paying for a custom shaft that would be trash the instant you upgraded joints.
  • Even though different in design, both inner and outer joints are similar in strength. The weak link in the shaft is the shaft itself.
After learning all of this, at least if you're set on RCV products, there does not seem to be a way around the initial $5000+ hit of custom shafts.

To start on a budget-build with the intent of upgrading later one would have to know stock applications of 934 joints with a list of shaft lengths and design to fit two of them. But this would leave you with a spline limitation at the UB that would likely come back to bite you.

So basically no way around aftermarket for your first set of shafts.
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I'm also IFS curious and have been messing with a '04 2500HD (complete single cab 6.0L truck) off and on (mostly off) for the last couple years. Only details really pertinent to the conversation right now is that our lift revealed some differences in available angle in factory replacement 2500 shaft. Factory shafts would spin at full droop and full steer with our BDS coilover setup but a set of Cardone replacements wouldn't. This makes me wonder about how much of people hating on IFS comes from simple problems like putting in "HD" replacement shafts that grenade the first time you steer them at full droop. Because you didn't know to check that detail which as has been said a lot of times here is just one of a lot of details that are important.

Just to clarify on the shaft cost above, the RCVs run about $2500. To get to $5K you'd have to be doing something pretty special with the stubs. I have a pair of the fleece diff shafts on the floor here to try out at some point and running a pair of the shorts might work well in a cut down 9.25 diff to get a good level of strength.

One question I had mostly for Mosebuilt (or anyone that has run the 9.25" hard in custom stuff) is how the snapring stubshaft retention system works out? It doesn't seem like a super robust system for dealing with resisting plunge forces and the number of shafts that get stuck in the factory diffs seems to bear that out. Any tips for making that system work better?

party on!
 
Stephen said:
Just to clarify on the shaft cost above, the RCVs run about $2500. To get to $5K you'd have to be doing something pretty special with the stubs. I have a pair of the fleece diff shafts on the floor here to try out at some point and running a pair of the shorts might work well in a cut down 9.25 diff to get a good level of strength.
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Oh, you're right. Their picture shows one shaft but I see now that the description says "set." I'll amend my post.
 
arse_sidewards said:
I don't see that being an issue. Tons of places will cut and roll splines on any axle shaft you want to send them. If you give them a shaft to copy they're even happier.
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Right. But the spline and length going into the stock tripod joint is likely not going to also fit the RCV 934 inboard joint. So you would be buying a temporary custom shaft that would be useless once you upgraded. That or you would be forever locking yourself into stock joints. To my knowledge, there is no aftermarket tripod joint that matches the stock one.

I don't have any reference as to if the tripod design is stronger or weaker than the Rzeppa design, but just looking at the thin shell, I bet the tripod is weaker by design.
 
Stephen said:
One question I had mostly for Mosebuilt (or anyone that has run the 9.25" hard in custom stuff) is how the snapring stubshaft retention system works out? It doesn't seem like a super robust system for dealing with resisting plunge forces and the number of shafts that get stuck in the factory diffs seems to bear that out. Any tips for making that system work better?
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I'm running RCV's in my TTB setup so I have that issue on the passenger side (albeit with the shaft pulling out of the CV ball). It's fun when that happens, it doesn't do the polite thing and just come all the way out, you're left with about 1/2 the spline engagement in the ball which then shreds the splines on both the shaft and the ball so both end up wrecked. I have some I can grab pictures of.

Their 'fix', as it is, is to use a square-profile snap ring instead of a round one. And then really hope you never have to take it apart again. I tried once, just to see, and after beating the crap out of it with a custom slide hammer got nowhere. Luckily it's not something I should ever need to do (the diff side is held by the center pin/regular C-clip), but it's not a very elegant fix.
 
I was mostly wondering about the snapring retention in the stock 2500HD diff setup, same ring you're talking about on the RCVs is used to keep the diff shaft in the diff. But in stock GM stuff they get pulled around and snarfed up and then you have to cut the shaft up to get it out. Not ideal obviously.
 
Stephen said:
I was mostly wondering about the snapring retention in the stock 2500HD diff setup, same ring you're talking about on the RCVs is used to keep the diff shaft in the diff. But in stock GM stuff they get pulled around and snarfed up and then you have to cut the shaft up to get it out. Not ideal obviously.
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What other designs are there to hold them in? Those snap rings are used in nearly all FWD cars that I've ever known as well as RZR's.
 
I don't have anything against RCV, but what other aftermarket options are there?
 
patooyee said:
Right. But the spline and length going into the stock tripod joint is likely not going to also fit the RCV 934 inboard joint. So you would be buying a temporary custom shaft that would be useless once you upgraded. That or you would be forever locking yourself into stock joints. To my knowledge, there is no aftermarket tripod joint that matches the stock one.

I don't have any reference as to if the tripod design is stronger or weaker than the Rzeppa design, but just looking at the thin shell, I bet the tripod is weaker by design.
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I meant that if you get your bling RCVs and the shafts are the wrong size then it's an extra $500 (probably less) to make something that's the right size.
 
patooyee said:
What other designs are there to hold them in? Those snap rings are used in nearly all FWD cars that I've ever known as well as RZR's.
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Subaru uses a stub shaft and a female spline in the bell of the plunging CV. There is a hole in both and a roll pin that holds them together. The Ford 8.8 and 9.75 use their usual C clips and have flanges the CVs bolt to.
 
patooyee said:
Right. But the spline and length going into the stock tripod joint is likely not going to also fit the RCV 934 inboard joint. So you would be buying a temporary custom shaft that would be useless once you upgraded. That or you would be forever locking yourself into stock joints. To my knowledge, there is no aftermarket tripod joint that matches the stock one.

I don't have any reference as to if the tripod design is stronger or weaker than the Rzeppa design, but just looking at the thin shell, I bet the tripod is weaker by design.
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I don't really know, but I too would think the tripod joint is inferior. Most in stock applications seem to wind up splitting apart from what I have seen due to the thin shell, but I think the bigger issue is the only 3 points of contact or torque transfer. The rzeppa design has what 6-8 balls in there to do the same thing. I think for the OEMs the tripod is just easy and cheap to make and has a lot of plunge to deal with misalignment issues and is "good enough" to work.

Kevin
 
Ghetto Fab. said:
I don't really know, but I too would think the tripod joint is inferior. Most in stock applications seem to wind up splitting apart from what I have seen due to the thin shell, but I think the bigger issue is the only 3 points of contact or torque transfer. The rzeppa design has what 6-8 balls in there to do the same thing. I think for the OEMs the tripod is just easy and cheap to make and has a lot of plunge to deal with misalignment issues and is "good enough" to work.

Kevin
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That's my gut instinct as well.
 
patooyee said:
To start on a budget-build with the intent of upgrading later one would have to know stock applications of 934 joints with a list of shaft lengths and design to fit two of them. But this would leave you with a spline limitation at the UB that would likely come back to bite you.

So basically no way around aftermarket for your first set of shafts.
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You're overthinking this.

Assuming you're using the OE Chevy 2500hd/3500 center:

To do this on the cheap and to make sure things work the way you want, use the OE outer CVs and tripod joints to get started with. Just have someone like Dutchman cut you a set of shafts to match the OE inner/outer joint splines and your needed length. Run them, double check everything and then go to a set of 934.5 CVs (35 spline) and either the spherical RCV outer with the orange boot or another 934.5 CV at the outer end.



patooyee said:
J
[*]The outboard joint is the same joint used on the Chevy SFA shafts. It is 35-spline where the shaft goes into it. I asked if it was a 934/935 joint for strength comparison and they said it was "comparable" but not a 934. It is their "spherical version" of a 934 joint, which allows them to use their plastic boot to seal it. I don't know exactly what that means, it's just what they told me.
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The RCV "spherical version" of a 934 joint is basically the D60 sized RCV with the orange boot we all know.

d60-rcv.jpg





Stephen said:
One question I had mostly for Mosebuilt (or anyone that has run the 9.25" hard in custom stuff) is how the snapring stubshaft retention system works out? It doesn't seem like a super robust system for dealing with resisting plunge forces and the number of shafts that get stuck in the factory diffs seems to bear that out. Any tips for making that system work better?
Click to expand...

First off, get plunge to a minimum. Why design for extra plunging forces if you don't need? I ran snap ring retained inner stub shafts with 930 CVs in my long travel 4Runner, 11" of travel and never pulled an inner stub out due to plunge. Why? Because the physical plunge didn't exceed the plunge of the CV

As far as different styles of retaining stub shafts:
  • The most common in the OE world is the snap clip. They work good and conserve space.
  • The most common in high performance applications is a captured bearing on the stub shaft that is retained by a bolt-on plate. BUT it does add the thickness of the bearing to the center housing.
  • One uncommon way is to have the stub shaft drilled and a long bolt goes through the stub shaft into the center of the diff where it screws into a washer or center block. There are a couple OE IFS/IRS centers that use this method. Nissan is the first that comes to mind.
That said, if using a snap ring to retain your stub axle, make sure the differential (locker or other) is designed to have a snap ring'd shaft in it. The differential side gears should have a landing or snap ring groove in side the side gear. The ID of the bearing journal should have a press in wear bushing that the shafts fit nicely (think of an outer stub going into a spindle bushing on a live axle).
 
Tech Tim said:
You're overthinking this.

Assuming you're using the OE Chevy 2500hd/3500 center:

To do this on the cheap and to make sure things work the way you want, use the OE outer CVs and tripod joints to get started with. Just have someone like Dutchman cut you a set of shafts to match the OE inner/outer joint splines and your needed length. Run them, double check everything and then go to a set of 934.5 CVs (35 spline) and either the spherical RCV outer with the orange boot or another 934.5 CV at the outer end.
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That method is a waste of a set of custom shafts ultimately.

Plus, I'll be designing in solidworks first so I think I can nail shaft lengths the first try.

I don't think the gm dif is worth messing with. 5.38 gears are the lowest offered and, as far as I can tell, lunchbox lockers and arbs are all that are offered for it, neither of which I am interested in.
 
patooyee said:
That method is a waste of a set of custom shafts ultimately.

Plus, I'll be designing in solidworks first so I think I can nail shaft lengths the first try.

I don't think the gm dif is worth messing with. 5.38 gears are the lowest offered and, as far as I can tell, lunchbox lockers and arbs are all that are offered for it, neither of which I am interested in.
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You're getting ahead of yourself. You will learn so much building an IFS for any given application. Your first one is guaranteed to suck compared to your second. In light of that you should run tires small enough to work with available gears, OEM joints, cut/welded/sleeved stock shafts until you figure it all out and then once you've got all the geometry out you can spend stupid money on shafts. Nobody builds a vehicle that wins anything their first try. Stop prematurely optimizing.
 
arse_sidewards said:
You're getting ahead of yourself. You will learn so much building an IFS for any given application. Your first one is guaranteed to suck compared to your second. In light of that you should run tires small enough to work with available gears, OEM joints, cut/welded/sleeved stock shafts until you figure it all out and then once you've got all the geometry out you can spend stupid money on shafts. Nobody builds a vehicle that wins anything their first try. Stop prematurely optimizing.
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Perhaps you have missed where I said I already have gears, tires, etc? So in light of that you are saying I should not try at all since I will not use a gm ifs?

Gm dif is super wide as well. Yes it can be narrowed, but then you're throwing another custom shaft at a turd.
 
patooyee said:
Perhaps you have missed where I said I already have gears, tires, etc? So in light of that you are saying I should not try at all since I will not use a gm ifs?

Gm dif is super wide as well. Yes it can be narrowed, but then you're throwing another custom shaft at a turd.
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Yes I missed it. Since you have 9s that are already built how you want that you want to use you should copy what Scott did and run the most compact housing that you can, run whatever wheel bearings and seals your axle would use in a semi-float application and then make what is basically a super-short semi-float axle and drill the flange for whatever bolt pattern your preferred CV uses.

Were a GM diff actually an option it would likely be easier since you would just replace the long side tube with a block off plate (which would be a simple exercise in machining precisely located circles into an aluminum block) that replicates the other case half allowing you to run an OEM driver side stub and seal on the passenger side as well.

The 9" solution will likely come out wider but I'm not sure how much it will matter since you are doing rear engine and packaging everything up front will be stupid easy compared to front engine.
 
patooyee said:
Perhaps you have missed where I said I already have gears, tires, etc? So in light of that you are saying I should not try at all since I will not use a gm ifs?

Gm dif is super wide as well. Yes it can be narrowed, but then you're throwing another custom shaft at a turd.
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apparently it's not too hard to narrow the 9.25 to use 2 factory GM short sides. That makes the inner shafts pretty budget friendly. You're still stuck with an adapter plate to run a 934-ish inner CV with a custom length shaft to even use the GM outer CV. That's probably the most effective while somewhat budget friendly front drive system available. Probably fine to use fairly hard with 35-37" tires depending on the terrain, driver and all the million other details that matter. Again mosebuilt has been doing it for a decade plus with apparently some pretty good results.

Problem is for a rear engine application you turn the GM front over and now it's going the less good direction. It's been done and isn't terrible but it is less good. It's still probably the best value package so far. I am a little intrigued by Jantz's youtube project using a D60 for an IFS center.

Patooyee, the only thing that might be good to consider changing about your parts pile might be to step down in tire size since we're in the same situation as a solid axle car with a lot of this. A build with 37" tires is much more forgiving than with 40s. Maybe IFS is a different in that it might be so much easier to build strength into the parts that it (tire size) matters less but bigger is always harder on steering parts and drive parts. But, part of the fun of all this is building that puzzle.
 
Stephen said:
apparently it's not too hard to narrow the 9.25 to use 2 factory GM short sides. That makes the inner shafts pretty budget friendly. You're still stuck with an adapter plate to run a 934-ish inner CV with a custom length shaft to even use the GM outer CV. That's probably the most effective while somewhat budget friendly front drive system available. Probably fine to use fairly hard with 35-37" tires depending on the terrain, driver and all the million other details that matter. Again mosebuilt has been doing it for a decade plus with apparently some pretty good results.
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If you could use two short side shafts then you could eventually get the RCV CV to fit it without an adapter. Still just seems like a lot of trouble to go through to use a somewhat inferior dif.

Stephen said:
Patooyee, the only thing that might be good to consider changing about your parts pile might be to step down in tire size since we're in the same situation as a solid axle car with a lot of this. A build with 37" tires is much more forgiving than with 40s. Maybe IFS is a different in that it might be so much easier to build strength into the parts that it (tire size) matters less but bigger is always harder on steering parts and drive parts. But, part of the fun of all this is building that puzzle.
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I agree with what you're saying but I just have zero desire to build on less than 40's. Until now the smallest tire I've ever ran was a 43. 40 was my compromise with myself. :) I feel like I have the parts pile to handle it. Plus, it seems like there is no between for some folks in this discussion. It's like, if we're not talking $60,000 we must be talking a six pack and a wad of ABC gum traded for parts from a cud-chewing junkyard redneck. I'm somewhere between those. I'd rather spend more on stronger parts than lose money selling my parts for inferior crap.
 
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We're really hindered by the fact that there is no really big readily available source for factory beefy IFS drive parts like we find in the solid axle world. I know there's some big stuff in the military world, anybody know anything about it? Obviously if it hasn't come up over the last 10 years it's not "readily available" but maybe there's something big out there we can rob parts from?

Similarly, how bad are the cheap 934 CV joints? Do we really need RCVs to make this stuff work reasonably?
 
Those empi joints are probably about as cheap as it's going to get and just what I was curious about. Sticking those on a GM stub with an appropriate adapter plate then running a custom shaft to a factory GM outer CV is the contender for "best budget solution" I mentioned above. This is essentially what RCV does but they do it with better materials than what might work OK for lighter duty stuff.
 
Don’t kill the messenger here. But what about H1 diffs? They are narrow already, have readily available gears and lockers. Not sure you’d call them beef but the hard work is done.
 
JR4X said:
Don’t kill the messenger here. But what about H1 diffs? They are narrow already, have readily available gears and lockers. Not sure you’d call them beef but the hard work is done.
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Factory inboard brakes is a sweet benefit for sprung weight as well
 
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