944Hybrids: 924/944/968 and 928 V8 Conversions
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Mon Jul 08, 2013 3:56 pm by Admin

For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Post  Cooksauce on Wed Nov 30, 2016 6:10 pm

I am looking to dive into an LSx v8 swap, but I'm trying to plan my approach first. Most of the research that I have done has led to concern about the trans. My goal is a car that I can hammer on (what's the point of the v8 if you can't use it?). My searching has led me to these conclusions:

1. A turbo box with N/A fifth gearset is the best, reasonably attainable gearing for an LSx.
2. The AOR box is the strongest, differing from the 5R, 5P, 9U, and UY only by the shot peened input shaft.
   (ignoring LSD and cooler)
3. Typical failure modes that I have found for the 944 transaxles are R&P, and cracking of the case. Which leads to the question, why did they decide to shot peen the input shaft? My thoughts are that this was done more for the shaft itself than the gears machined on it (possibly to help with torsional displacement because max shear stress resides on the outer diameter of the shaft; the main area that shot peening affects).

Right now my plan is to use a 5R and cryo treat the R&P, use TPC's reinforcement plate, and use a stronger mounting setup to limit flexing of the case. I've found that the most are willing to part with the 5R for less money than the AOR, which is the main reason behind that choice.

- Has anyone sheared, or heard of anyone shearing, their input shaft or first/second gears? (on any 944 box)
- Does anyone think it would be worth the teardown/assembly time to cryo treat the input shaft and gearsets?

If anyone sees any incorrect info please let me know. Also, if anyone thinks starting with the AOR box would be better or has other constructive input please comment and give a little support on your comment.

I'm looking forward to jumping in here, and plan to be pretty active. Thanks for any help you guys have.


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Join date : 2016-11-28

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Post  sharkey on Wed Nov 30, 2016 10:08 pm

my research on the AOR indicated that its not the input shaft itself thats shot peened, its 1st and 2nd gear thats shot peened. the shot peening removes stress risers, doing it would make the teeth of the gears less prone to breaking. that being said, ive never seen pics or heard of anyone breaking 1st or 2nd gear in any 944 transaxle, the weak part seems to be the ring gear. the case is weak in the non turbo transaxles, excluding the s and s2 (aos and aot) as they are the same as the turbo transaxe aside from the final drive ratio. the problems with the case on these transaxles is actually the bearing support in the center, the pinion loads rear bearing and it breaks the casting, this is what the reinforcement plate is designed to stop. turbo transaxles (and aos/aot) didnt have this problem as they beefed up the casting.

imo, i dont think the aor is that much better than any other turbo box if your not considering the lsd or cooler. now adding those things in, the lsd in the aor is the strongest of any of the 944 transaxles. that being said, none of the diffs themselves are that weak, and you can mix and match the clutches to come up with more holding power on any of the diffs.

as for cryo treating, ive built a lot of transmissions and never done it, so its hard for me comment. a lot of people claim it does a lot. imo if your gonna strip it down to get the ring and pinion out and cry them, may as well strip the input shaft down to and send all the gears and shafts in.

just one more thing to add, as the turbo transaxles will take quite a bit of a beating, dont expect to be doing line lock burnouts all the time, you will kill it. no matter what we do with these transaxles we are still limited by the size of the parts inside, and they just dont take shock loads from 2-3x the torque than the cars came with.


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Post  Cooksauce on Wed Nov 30, 2016 10:41 pm

Interesting, I figured they would have treated the entire shaft since 1st and 2nd are machined into the shaft. To your point about the bearing support and reinforcement plate, do you see the plate as redundant/pointless? Does having it in there have drawbacks? Thanks for the help


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Post  sharkey on Thu Dec 01, 2016 1:27 am

i went back and re-read some info, one source says "the input shaft, 1st gear were shot peened for added strength". another source said "1st and 2nd gear are shot peened". so who knows exactly.

the plate is quite possibly redundant in the turbo transaxle, ive read info saying its not needed, others swear by it. i have an AOR going into my swap (its a little different, its a gm 2.2l ecotec, currently putting down 325 whp, next year ill be upping the boost to around 450 whp, and an ultimate goal is around 600). when i pull it apart im going to be putting the reinforcement plate in.


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