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Ifs 101
- Thread starter patooyee
- Start date
Provience
Kill!
pretty easy to do with any IFS center chunk, biggest problem is packaging space for the rotors
arse_sidewards
Contrary to everything
- Joined
- May 19, 2020
- Member Number
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- 8,209
AMC 20 is barely better than any other half-ton axle. Holds up fine with portals but without them it's toast.
I still want a part number to look up a factory 934 joint somewhere. I can't seem to find any resource that states what the factory application is other than "turbo Porsche." I know it's probably made of pot metal, but my curiosity requires satisfaction nonetheless. :)
I know. They’re 1/4 ton diffs but they come with torsion lockers, narrowed already and with CV flanges. Only plus is the hard work is done. Compact narrow and already bossed to be mounted as a centered diff.
I can’t use them because 4.88’s as the lowest available ratio is a million miles from what I need. Just thought I’d throw it out there, someone might be able to test proof of concept with them.
AgitatedPancake
Frobot
That is a very good question that I wonder as well. Just for random example, here is what came up on rockauto with a random year 944 I chose. A full half shaft with two CVs at a whopping $38 if you're literally starting at the most basic and just testing a proof of concept, so it may be ok that they're cheap and/or weak.
*probably not a 934, for clarity. Just reference to cheap shafts once we discover the original application*
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arse_sidewards
Contrary to everything
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I could be wrong but that doesn't look like a 934. Pretty sure the 934 bolt circle is 6x108mm.
AgitatedPancake
Frobot
Let's be honest here, it's $48 after shipping
Bahaha right.
Hmmm fair point, like you I don't know what they come from so I just picked a random one. But once we find the proper factory application, we might be able to find the correct shafts for dirt cheap
This looks like it might be a 934:
https://www.rockauto.com/en/moreinfo.php?pk=9160100&cc=1431383&jsn=1379
Kartec offers multiple levels of cv joints depending on budget:
https://www.kartek.com/parts-categories/cv-joint-assemblies.html
https://www.kartek.com/parts-categories/cv-joint-assemblies.html
Tech Tim
Your AD Here....
The problem with big military stuff is it's big and heavy and designed for roadside bombs, not long travel.
The GM 3500 IFS parts is probably the best one ton IFS starting point if you want to use factory based parts. The spindle upright geometry is decent, uses standard 8 lug (8x6.5) unit bearings and the brake are decent. The earlier center section is really easy to narrow, but it is big. Haven't looked at the later model center, they looks a little smaller because it's not a clamshell.
We like the 9" center the best. You can design/weld the housing right into the bulkhead for a super tight package and better clearance.
They are chinese made, EMPI originally made Trail Gears dirty 30 Toyota birfs. I haven't ran the 934s, but have ran the 930s and they were decent enough. Take them apart and do a full race prep on them and use some high quality CV grease and give them a try. Worst case you're only out $125.00
The nice thing about the 934s is that even the high end one are not that expensive.
Kartek sells 35 spline 934s for $400.00. Those are genuine Lobro GKN joints, good stuff.
H1 diffs are a Model 20 (yes, like 70s Jeep model 20), so you are limited on gearing choices. The inboard brakes make for a wide center section, don't remember what the flange to flange is off the top of my head.
iirc - They also run a funky ring gear offset.
Stephen Wilson
Well-known member
It appears that there was no "production" car that used the 934 cv, it's only on the limited production factory homologated Porsche 934 (then 935/917) race car.
This isn't really an important issue, as I wouldn't use a stock one anyway. But you sure about that? That link I posted earlier has the 934 bolt pattern. I think it was 2005 - 2008 911 turbo. So if it's not a 934, it's something with the same bolt pattern.
Do you not soft-mount them at all?
Isdtbower
In for Tech
BUDGETS
Tim: Lets estimate some numbers for "hard parts" Not the Fab parts like bulkheads, arms, uprights, and Normal parts like brakes, wheels. etc .
As I thought about a U4 IFS build list, there is a minimum which can be easily exceeded with just the Diff ( $30k), and now, portals. So basics only. All arguable.
Diff: $6k +
CV's : 2ea 934.5/935, 2 ea Series30 $4 K
Half shafts: $1.5k
7/8 to 1" Rod ends and/or Bushings.$ 0.6K
1.5" spherical bearings - Upright: $0.5K
Spidertrax Upright unit bearings, builder bells, stub shafts: $4.2K
TT pump, Rack, servo/etc. steering: $7K
So I am seeing a minimum of $25K in go fast builder parts.... Which puts Bills and others, complete IFS commitment clip for $40k into perspective.
Tim: What do you see in a Chevy IFS conversion cost? Or even your High angle Toyota build?
Tim: Lets estimate some numbers for "hard parts" Not the Fab parts like bulkheads, arms, uprights, and Normal parts like brakes, wheels. etc .
As I thought about a U4 IFS build list, there is a minimum which can be easily exceeded with just the Diff ( $30k), and now, portals. So basics only. All arguable.
Diff: $6k +
CV's : 2ea 934.5/935, 2 ea Series30 $4 K
Half shafts: $1.5k
7/8 to 1" Rod ends and/or Bushings.$ 0.6K
1.5" spherical bearings - Upright: $0.5K
Spidertrax Upright unit bearings, builder bells, stub shafts: $4.2K
TT pump, Rack, servo/etc. steering: $7K
So I am seeing a minimum of $25K in go fast builder parts.... Which puts Bills and others, complete IFS commitment clip for $40k into perspective.
Tim: What do you see in a Chevy IFS conversion cost? Or even your High angle Toyota build?
Stephen Wilson
Well-known member
No, not 100% sure. If you're talking about post #340 I think the 108mm/28 spline (vs. 128mm/33 spline) makes it a Porsche 930 cv. I don't see anything saying it's a 108mm bolt pattern, just "108mm Bolt-On (6 holes)", not the same thing ?
Not trying to be a smart-ass, but I highlighted it for you.
Random 934 CAD model found on GrabCad:
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RadialDynamics
Yellow Skull
As a point of reference, I run 930 cv's on my 2wd Hayabusa buggy and just grabbed a few measurements. 108mm (4.25") describes the OD of the joint. Bolt circle appears to be approx. 3.75" (6 bolts).
mdogg
Member
- Joined
- May 20, 2020
- Member Number
- 786
- Messages
- 19
I've been following along and figure I have a bit of experience with the portal stuff I can share. Guys more knowledgable then me in this thread have hit on the many benefits to running portals already but it can be done on a budget.
I bought a portal IFS buggy from "tjmark" on pirate 4 years ago, I cant find the thread on pirate but this is a copy floating around:
http://www.4x4-16.com/75Fab-JV-Asssassin-IFS-Chassis_10854777.html
I have been racing it and found that the original build and parts did not hold up racing Ultra4 but would have no issue in a regular wheeler / play buggy. I was eating stock mog gears from shock load, breaking upper arms etc. those issues have been solved with $$$ but not the point off this post. I would guess this is going to be the cheapest/best strength compromise to get 4wd IFS in a buggy. This is the setup that was originally in this buggy. To date I have never had a diff, shaft or cv issue/failure
74weld Aluminum Portal boxes x2 = $1600
74weld Aluminum Hubs x2 = $800
Spidertrax rotors x2 = $300
Wilwood Caliper x2 = $270
NOS or USED Unimog portal box (includes 2.1 gears, bearings, and backing plates) x2 = $1000
8.8 out of explorer or hummer amc 20 = $300?
Ring/Pinion = $300
ARB Locker = $1200
Custom outer Stubs (mog to 930) x2 = $1200
Diff Stub Shafts (8.8 to 930) x2 = $600
Plunging 930 RCV’s x 2 = $450
Fixed 930 RCV x 2 = $400
28 spline 300m shaft x 2 = $600
Total $9020
You still need upper/lower arms, bulk head, knuckles, and steering to sort out.
I bought a portal IFS buggy from "tjmark" on pirate 4 years ago, I cant find the thread on pirate but this is a copy floating around:
http://www.4x4-16.com/75Fab-JV-Asssassin-IFS-Chassis_10854777.html
I have been racing it and found that the original build and parts did not hold up racing Ultra4 but would have no issue in a regular wheeler / play buggy. I was eating stock mog gears from shock load, breaking upper arms etc. those issues have been solved with $$$ but not the point off this post. I would guess this is going to be the cheapest/best strength compromise to get 4wd IFS in a buggy. This is the setup that was originally in this buggy. To date I have never had a diff, shaft or cv issue/failure
74weld Aluminum Portal boxes x2 = $1600
74weld Aluminum Hubs x2 = $800
Spidertrax rotors x2 = $300
Wilwood Caliper x2 = $270
NOS or USED Unimog portal box (includes 2.1 gears, bearings, and backing plates) x2 = $1000
8.8 out of explorer or hummer amc 20 = $300?
Ring/Pinion = $300
ARB Locker = $1200
Custom outer Stubs (mog to 930) x2 = $1200
Diff Stub Shafts (8.8 to 930) x2 = $600
Plunging 930 RCV’s x 2 = $450
Fixed 930 RCV x 2 = $400
28 spline 300m shaft x 2 = $600
Total $9020
You still need upper/lower arms, bulk head, knuckles, and steering to sort out.
Todd at Trail Worthy Fab will sell H1 diffs complete for $350 each. Just an FYI if anyone has any interest in them.
Those would probably be cool for building an IFS/IRS transaxle kids buggy on 35's, but are pretty much useless for anything else without using the portal ends.
Stephen Wilson
Well-known member
Not trying to be a smart-ass, but I highlighted it for you.
No problem. I saw that, but as radial mentions, it's not clear if that 108mm is the OD or the bolt circle. In general, cv's seem to be designated by OD, not bolt circle: the 930 is a 108mm cv, the 934 is a 128mm cv. IDK
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I’ve been painstakingly chasing down diff parts to do an IFS/IRS for 35’s. Best I’ve been able to piece together two 9” diffs for, spool rear, lockrite front, 31 spline inner shafts for 934 CV’s is coming in right around $5,000 dollars. $700 for two complete diffs is pretty enticing. If I could get 5.38’s for them I’d splurge for two of them. 4.88’s ain’t going to my project.
mdogg
Member
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- May 20, 2020
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- 786
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- 19
If its in a racecar id expect everything to be solid mounted. I use an aluminum bushing in place of stock rubber mount and solid mount off the diff cover.
You don't buy into the shock mitigation theory of soft mounting?
Maybe in a street vehicle, but for offroad use everything I've ever run across has been solid mounted. Take UTV'S and 4x4 ATV's for example, all the diffs on those are solid mounted. There may be a few exceptions but its not the norm.
Tech Tim
Your AD Here....
No, everything is made as tight as possible to keep ground clearance to a maximum. By welding the 9" housing right into the bulkhead we can reduce size and use the housing as part of the structure for strength.
Plus no reason to pull the housing out. Once it is in place, you only need to pull the 3rd member.
Yes. This ^ too.
Last I’m going to bring it up, and only in the interest of completing the thought train on them. These have 2.73 gears, if I understand correctly they have Torsen lockers in them. 29 spline inner axle shafts, Yukon lists 4.88:1 gears as the lowest ratio but they are H1 specific. Todd says he has 90 of them complete with inboard brakes.
If 29 spline shafts weren’t oddball I’d almost buy 2 just for the four short shafts. I could have two complete locked geared H1 diffs for $1,100 bucks vs the $5,200 I’m looking at for two complete 9” diffs.