Ifs 101

[patooyee]

Hey JJ, What is the build you're planning?

Maybe I missed it earlier?

I started on a single seat SFA rear engine rig several years back, but didn't get far. I have 95% of the parts already. Steering 9" axles using 05+ Ford UB outers, turbo Ecotec engine, etc. My goal was to be cheap, light, fun, but not out to win any contests. My goals are still to be cheap, light, and fun, but built more toward speed (A relative term with a 4 cylinder. Like 60mph is fast for me, not trying for 100+.) than rocks, and now I'd like to fit another seat as well. Ideally I'd like to keep my current rear axle the way it is and use as many of my front end parts on the ifs as possible.

 

[YotaAtieToo]

Not exactly, but exactly. I’ve been into racing for quite a while. Have had the opportunity to co-drive in some of the big name U4 cars including getting to co drive the finals in Bailey Campbell’s IFS car. Even with no overdrive 40’s and 6.20’s will go 107 mph at 7000 rpm. Most will never touch those kinds of speeds in an off road car. Jesse Haines JHF portal axles are running in the neighborhood of 7:38:1 if not lower, final axle ratio and taking the comp scene by storm.

I’ve come to find that 5:38’s and 40’s is a sad compromise in light of say 6.20’s or 6.50’s. I’ve found absolutely zero reason to not run the lower diff gears now. My favorite crawler combination so far is a 700R4 trans, 4.3 atlas and 5.38’s in the axles. That’s 71:1 low range, can still do 55 in low with 40’s at 6000 ish rpm.

If for some reason you’re limited in horse power or for some reason drivetrain length. Most common 3 speed auto’s are 2.50:1 ish first gear vs 3.07:1 that the 700 has. By running 6.50’s with a regular 3 speed auto, 4.3 t-case you end up with 69:1 crawl ratio. Close enough to the crawl ratio I find works best. Yet still low enough that high range is useable for big heavy tires.

I don't have any of the U4 experience that you have, but agree. I think hp D60 6.17s would be a huge money maker, toyota guys did it for a while. But all those gm60s are dried up and everything is driver drop now a days. 5.38s are really only good for 35-37s on most 4cyl or v6 rigs. The JK crowd would greatly benefit from 6.xx gears imo. Most JK guys say the 5.38s are great on 35s, and OK on 37s.

Having more of your gearing in your axles also takes stress off of the rest of your drivetrain, less axle wrap and less tq lean. I believe Jesse is running more like 9.7 effective axle ratio. Lame reference, but the rc crawler world figured this out a while ago. The typical ~3:1 axle rigs have a lot of tq lean, while the ~8:1 worm drive or portal axle rigs have almost none. They also commonly run faster ratios in the front to help with turning radius and climbing.

Anyway, sorry for the derail.

 

[JR4X]

I don't have any of the U4 experience that you have, but agree. I think hp D60 6.17s would be a huge money maker, toyota guys did it for a while. But all those gm60s are dried up and everything is driver drop now a days. 5.38s are really only good for 35-37s on most 4cyl or v6 rigs. The JK crowd would greatly benefit from 6.xx gears imo. Most JK guys say the 5.38s are great on 35s, and OK on 37s.

Having more of your gearing in your axles also takes stress off of the rest of your drivetrain, less axle wrap and less tq lean. I believe Jesse is running more like 9.7 effective axle ratio. Lame reference, but the rc crawler world figured this out a while ago. The typical ~3:1 axle rigs have a lot of tq lean, while the ~8:1 worm drive or portal axle rigs have almost none. They also commonly run faster ratios in the front to help with turning radius and climbing.

Anyway, sorry for the derail.

Not a derail, that’s all part of the equation. Talking to a comp buggy builder right now about the portal builds. The car that won the 2020 trailhero trail breaker was 10.1:1 final axle ratio. 1.92:1 portals with 5.29:1 diff gears.

10.1:1 Is useless as a high range for a go fast rig obviously. For the torque transfer control you’re talking about they are running stock D300 t-cases with 2.62:1 low, normal 3 speed autos for 65.5:1 crawl ratio. This puts most of the reduction in the axles instead of trying to transfer it to the diffs through the driveline which is hard mounted to the chassis, inducing body roll in a bind.

For the IFS go fast stuff on topic, we want the middle ground. I think that middle ground is 6.50:1 diff gears for 37”+ tires regardless of what engine/trans combination you’re planning to run. It’s also important that you start designing your IFS around the diff as it will be a serviceable part. Once you’ve built your pivot points around the CV spacing, you can’t easily switch from 14B diffs to 9” without causing ripples to the rest of your plan.

 

[YotaAtieToo]

Not a derail, that’s all part of the equation. Talking to a comp buggy builder right now about the portal builds. The car that won the 2020 trailhero trail breaker was 10.1:1 final axle ratio. 1.92:1 portals with 5.29:1 diff gears.

Gotcha, I thought H1s were 1.8:1, so my math was off a bit.
​​​​​​

10.1:1 Is useless as a high range for a go fast rig obviously. For the torque transfer control you’re talking about they are running stock D300 t-cases with 2.62:1 low, normal 3 speed autos for 65.5:1 crawl ratio. This puts most of the reduction in the axles instead of trying to transfer it to the diffs through the driveline which is hard mounted to the chassis, inducing body roll in a bind.

I don't think it's too low even for go fast. How many guys bomb around fire roads and the desert in a ~2;1 low with 5.xx gears? The only thing I wonder is what other effects there are. I would wonder about pinion bearings being spun 2x's as fast as normal. You're probably right though 6.xx is probably the best all around.

For the IFS go fast stuff on topic, we want the middle ground. I think that middle ground is 6.50:1 diff gears for 37”+ tires regardless of what engine/trans combination you’re planning to run. It’s also important that you start designing your IFS around the diff as it will be a serviceable part. Once you’ve built your pivot points around the CV spacing, you can’t easily switch from 14B diffs to 9” without causing ripples to the rest of your plan.

Fair point, it's hard to not use a 9" for a lot of things. The support and options are hard to match.


Quick Google turns up these. It's dynatrac, so probably $$$, but options are always good.

Edit: from what I read, the empty center is ~$2400. I'm assuming that includes the Stubs, but not certain.

https://www.dynatrac.com/blog/proroc...s/#comment-241

https://www.fourwheeler.com/how-to/1...hd-ifs-option/

 

[TRINDU]

I was thinking y'all were talking about low buck, garage type, IFS builds. Keep it going as the tech is the same. Ill keep reading and figure out how to make a LC100 diff work in my 4runner.

 

[Sterlingfire]

I was thinking y'all were talking about low buck, garage type, IFS builds. Keep it going as the tech is the same. Ill keep reading and figure out how to make a LC100 diff work in my 4runner.

It was about garage builds and reusing stock parts. It's now about big money ifs diffs and trying to achieve 20" of wheel travel.
Don't get me wrong it's great tech, but not the focus of the op. I know the basic ideas will transfer, and cost is relative, but imo we're off topic now considering maybe one of these guys is going to build a high end ifs car before we die:rolleyes:

I myself have been interested in ifs for a long while. The only reason my truck went sfa is because i didn't want to get into the complications of making the ifs jive together without much experience in that world. I now feel confident enough to start gathering some parts for my wife's gm truck. It will probably use Ford raptor uca's, lca's, knuckles, brakes, ub's, and maybe shocks. I can get at least 12" of reliable travel from this setup, and am thinking 14" Is not out of the realm, depending on if i can keep the cv's alive. Raptor guys are running 37" tires and making parts live, so why can't we? The best part is that if i ever felt the need for more travel, bolt on parts for raptors are plentiful, and avaliable right away. Obviously have to deal with the same stuff this thread is talking about, but having a stock rig to take measurements from is going to be the key to making this easier for me. I don't need to design the whole system, just small portions of it.

 

[arse_sidewards]

If you want a low buck 15" of IFS wheel travel you do a TTB and live with the shitty camber change. When you get sick of the middle joint blowing up you call RCV and give them your credit card number.

 

[JR4X]

I do want it to be cheaper. I just don’t know how to get there. I don’t have a lathe or end mill and can’t spline shafts on my own. My cheap little RZR has 18” of front wheel travel, and 20” in the rear. If I could just get diffs built it would be pretty easy to copy that stuff on the cheap.

9” thirds are cheap enough. It’s a case and inner shafts I can’t work out for super cheap.

 

[JR4X]

Fair point, it's hard to not use a 9" for a lot of things. The support and options are hard to match.


Quick Google turns up these. It's dynatrac, so probably $$$, but options are always good.

Edit: from what I read, the empty center is ~$2400. I'm assuming that includes the Stubs, but not certain.

https://www.dynatrac.com/blog/proroc...s/#comment-241

https://www.fourwheeler.com/how-to/1...hd-ifs-option/

Looks like that’s everything but a locker/carrier gears and a diff cover. Buts about the same cost as the 9” cans and shafts From spidertrax or Currie too.

The 1.8:1 portals are 10K’s, I guess the 12K’s got a little lower ratio.

 

[arse_sidewards]

It can't be that hard to replace all the stuff on the long side of a GM or Ford IFS diff with a block off plate and bearing that let you run a short side stub.

It can't be that hard to flip over a D44 or Ford 8.8 IRS 3rd member, add an oil channel, run high pinion gears and use whatever wacky bearing and shim setup it takes to make it all fit.

 

[Sterlingfire]

If you want a low buck 15" of IFS wheel travel you do a TTB and live with the shitty camber change. When you get sick of the middle joint blowing up you call RCV and give them your credit card number.

Why when that will take even more work for less reliability, and be shittier to drive?
The raptor ifs would be less work to fabricate onto the truck, be easier to setup properly, and can be acquired for less than 1200 including the shocks. The biggest deal will be cv's and making sure everything is aligned.

I do want it to be cheaper. I just don’t know how to get there. I don’t have a lathe or end mill and can’t spline shafts on my own. My cheap little RZR has 18” of front wheel travel, and 20” in the rear. If I could just get diffs built it would be pretty easy to copy that stuff on the cheap.

9” thirds are cheap enough. It’s a case and inner shafts I can’t work out for super cheap.

Wasn't calling you out specifically, more the guys who are saying 30k center chunks and using portals is the only way to build one...i get the complications with the center chunk, but surely there is an easier, less expensive way to get there, depending on how much travel you're looking for.

 

[YotaAtieToo]

I was thinking y'all were talking about low buck, garage type, IFS builds. Keep it going as the tech is the same. Ill keep reading and figure out how to make a LC100 diff work in my 4runner.

Which size is the 100 diff? I'd like to just graft everything from a 4th gen 4runner/FJ cruiser onto my 4runner.

Looks like that’s everything but a locker/carrier gears and a diff cover. Buts about the same cost as the 9” cans and shafts From spidertrax or Currie too.

The 1.8:1 portals are 10K’s, I guess the 12K’s got a little lower ratio.

Ya, similar price, but most of the D60 shit is stronger. Isn't the 9" Arb weak unless you spend stupid money? I'm a drop out 3rd fan, but from a lot of research I did last spring, the 9" really isn't that strong. Sure there are the 10" gears, but they're soft and get changed out often. I haven't seen any high hp rigs running the 6.50s.

Even Currie wouldn't sell me a 9" rear, they actually recommended a hp60 rear over the 9" stuff.

It can't be that hard to replace all the stuff on the long side of a GM or Ford IFS diff with a block off plate and bearing that let you run a short side stub.

It can't be that hard to flip over a D44 or Ford 8.8 IRS 3rd member, add an oil channel, run high pinion gears and use whatever wacky bearing and shim setup it takes to make it all fit.

The gm diff is all aluminum right?

is that how it works? Just flip it over and run HP gears?

What about the D50 ttb diff it's self? I think it was spider who modded one into an IFS center. The 9" r&p, then there is the option for Jana 56 kit.

 

[YotaAtieToo]

9" vs D60 moved to a new thread, sorry for derail

 

[TRINDU]

Which size is the 100 diff? I'd like to just graft everything from a 4th gen 4runner/FJ cruiser onto my 4runner.

High pinion 8, same R&P as the 80. But its passenger drop. Was looking into a Supra IRS for center diff, but dont want the diff as a plow. Doesnt seem to be too much of an advantage with stock frame width for A arms.

 

[YotaAtieToo]

High pinion 8, same R&P as the 80. But its passenger drop. Was looking into a Supra IRS for center diff, but dont want the diff as a plow. Doesnt seem to be too much of an advantage with stock frame width for A arms.

That's right, I forgot it's pass drop. 8" opens up more options for lockers as well.

I agree, I wanted to mess with the IFS on my 90 4runner also. The blaze land guy with the center diff way under the oil pan didn't get me excited.

 

[arse_sidewards]

The gm diff is all aluminum right? Yes

is that how it works? Just flip it over and run HP gears? I was glossing over all the fiddling with spacers/bearings you need to do and oil channel you need to add.

.

 

[YotaAtieToo]

.

You can not put HP gears in a LP housing, no amount of spacers shims or ferry dust will help

 

[TRINDU]

That's right, I forgot it's pass drop. 8" opens up more options for lockers as well.

I agree, I wanted to mess with the IFS on my 90 4runner also. The blaze land guy with the center diff way under the oil pan didn't get me excited.

Was never a fan of the blazeland stuff, he recently sold out to someone else who pays royalties now. Some scrap steel thrown at the a-arms to run T100 shafts with zero aftermarket support, doesnt really jive with me either.

The LC100 shafts look similar to the 96+ taco/4runner shafts. I ordered some off amazon to mic and compare. Would open up possibilities there. I just havent decided on which knuckles to cobble off of. Other wise, driver drop has tons of possibilities.

The biggest issue is do I give up the idea of KOH and trash the torsion bars. But if I did that I'd just chop and rebuild the front rails for something more advanced. I want to strip the 4runner to light weight anyways and run (mostly) parts I have on hand. I was never happy with any SAS I did or witnessed.

 

[TRINDU]

I do want it to be cheaper. I just don’t know how to get there. I don’t have a lathe or end mill and can’t spline shafts on my own. My cheap little RZR has 18” of front wheel travel, and 20” in the rear. If I could just get diffs built it would be pretty easy to copy that stuff on the cheap.

9” thirds are cheap enough. It’s a case and inner shafts I can’t work out for super cheap.

I think theres a separation between folks who "wheel" a D30 on 37s and make it last. Verse those of us who grenade parts on 31s.

RZR has the advantage of rubber bands and 1500lbs. Consider any vehicle based rig is 3000lb+, could you just copy the suspension by doubling the material, rods, etc. Or is the dynamics completely thrown off.

 

[arse_sidewards]

You can not put HP gears in a LP housing, no amount of spacers shims or ferry dust will help

Pinion is on the same side of the ring gear, is it not?

Vertical pinion offset from carrier centerline is the same from HP to LP, is it not?

If those two things are true the rest is just basic machine shop work.

 

[vetteboy79]

Pinion is on the same side of the ring gear, is it not?

It's not once you turn the diff upside down.

 

[YotaAtieToo]

Pinion is on the same side of the ring gear, is it not?

Vertical pinion offset from carrier centerline is the same from HP to LP, is it not?

If those two things are true the rest is just basic machine shop work.

Go hit Google, if it was that easy everyone would do it. Your missing a major detail

 

[Wilson]

It can't be that hard to replace all the stuff on the long side of a GM or Ford IFS diff with a block off plate and bearing that let you run a short side stub.

It can't be that hard to flip over a D44 or Ford 8.8 IRS 3rd member, add an oil channel, run high pinion gears and use whatever wacky bearing and shim setup it takes to make it all fit.

I mentioned it earlier, but Mosebilt did that with the big gm diffs. The conversation quickly derailed into a “stock aluminum diffs suck....”

 

[Wilson]

Go hit Google, if it was that easy everyone would do it. Your missing a major detail

so what’s wrong with these hp Sami axles I just threw under there. I flipped both 3rds over for hours. It’s ready to rock! I even added some semi truck mirrors so I can get a better look at where I’m going, without straining my neck!

 

[JR4X]

I think theres a separation between folks who "wheel" a D30 on 37s and make it last. Verse those of us who grenade parts on 31s.

RZR has the advantage of rubber bands and 1500lbs. Consider any vehicle based rig is 3000lb+, could you just copy the suspension by doubling the material, rods, etc. Or is the dynamics completely thrown off.

I’d like to find out. I’m actually entertaining the idea of putting aftermarket Turbo-S RZR suspension directly into a Geo Tracker. Affordable diffs is my big hang up. The correct gear ratio for the tire size I want to run is 6.83:1 and 9” is the only way to get there. My RZR weighs 2500# with me in it. The tracker weighs 2500# empty so they aren’t too far apart in weight.

I tried running a samurai t-case in one to take advantage of the high range gear reduction but the t-case is to weak and it was too easy to break it.

 

[TRINDU]

I’d like to find out. I’m actually entertaining the idea of putting aftermarket Turbo-S RZR suspension directly into a Geo Tracker. Affordable diffs is my big hang up. The correct gear ratio for the tire size I want to run is 6.83:1 and 9” is the only way to get there. My RZR weighs 2500# with me in it. The tracker weighs 2500# empty so they aren’t too far apart in weight.

I tried running a samurai t-case in one to take advantage of the high range gear reduction but the t-case is to weak and it was too easy to break it.

I have no experience or first hand knowledge of golf carts, but how reliable/robust are the portals? May be out of one hand and into the other for cost, but would open up the availability of thirds? With the added benefits of clearance.

 

[arse_sidewards]

Go hit Google, if it was that easy everyone would do it. Your missing a major detail

Ok. You win this one. The TTB 3rd member that was on my shelf was sitting upside down. Ring gear is on the wrong side.

 

[JR4X]

I have no experience or first hand knowledge of golf carts, but how reliable/robust are the portals? May be out of one hand and into the other for cost, but would open up the availability of thirds? With the added benefits of clearance.

They seem to be ok for durability but they raise the roll center pretty bad. They also give a lot of scrub radius.

 

[DMG]

Ok. You win this one. The TTB 3rd member that was on my shelf was sitting upside down. Ring gear is on the wrong side.

That’s almost as bad as that time someone inverted your soup spoon. Lucky mom was there or you might have starved.

 

[YotaAtieToo]

I’d like to find out. I’m actually entertaining the idea of putting aftermarket Turbo-S RZR suspension directly into a Geo Tracker. Affordable diffs is my big hang up. The correct gear ratio for the tire size I want to run is 6.83:1 and 9” is the only way to get there. My RZR weighs 2500# with me in it. The tracker weighs 2500# empty so they aren’t too far apart in weight.

I tried running a samurai t-case in one to take advantage of the high range gear reduction but the t-case is to weak and it was too easy to break it.

What were you breaking in the Sami case? Lot of guys running them with much bigger tires and axles.

Sxs diffs are stupid high like 3.30s, the normal portals are only 1.2:1 also.