944 Transaxle Ring and Pinion WITHOUT the Special Tools
 

Hi all,

For those of you who have seen my post about getting into 944 ownership (https://rennlist.com/forums/924-931-...fic-forum.html), I have torn the powertrain out of the '87 parts car and have pretty much gutted the interior (just have HVAC to remove). I have no idea of the state of the trans from the parts car but I know I'm looking at a trans rebuild in the '86 (difficulty getting into first gear and speed / power dependent whine from rear while driving) but I was going to plan to swap the '87 trans into the '86 and see what state that trans was in. But I know I'm looking at tearing into at least one of the boxes. I have found quite a few sources for used a used trans but again you're working with the unknown there as well.

So my question is, after having read Sean's GREAT trans walk through (https://rennlist.com/forums/944-turb...age-heavy.html), has anyone ever had any success setting up the ring (crown) and pinion WITHOUT the special tools? I have no access to the tools or any desire to track them down just to set pinion depth. I know it would take more trial and error but has anyone even done it the "traditional" way with painting the gears and adjusting based on the tooth pattern? It seems ridiculous to need $1000's in tools to set pinion depth.

And just FYI I was a master ASE mechanic for 10 years (but that was ~6 years ago), so I have done rearends before ,didn't specialize in them but have a basic working knowledge.

Just curious, thanks, Jason.

Send a PM to Kevin Gross, he is a respected 944 transmission rebuilder.

Look for a thread that I think was started by Tifosiman

I think he ended up using solder behind the bearing races to determine shim sizing. It was actually a suggestion that I made, as it was how I verified my ring & pinion when I did it.

Define what you mean by "success."

Success = A quite, long lasting gear set

I can appreciate the fact that these cars are German engineered and therefore everything was measured right down to .001 of a millimeter, but what makes the ring and pinion in this transaxle so unique that necessitates the use of the vw385 tools? Every other ring and pinion I've ever done (or seen done), be it in a traditional rear end or a transaxle, didn't require anything beyond the knowledge of reading the tooth pattern and making your shimming adjustments.

Everything else about setting the pre-load and backlash seems straight forward and could be done with common torque wrenches and dial indicators. So with the million dollar vw385 tool, with its fragile and (from what I can tell last 3 -4 on Earth have been purchased https://rennlist.com/forums/911-foru...help-pete.html) no longer available plastic cam, what process is being performed that the tooth patterns couldn't perform?

Scott I think I had read that post before but the search function on RL isn't the greatest... Would you happen to have the link or be able to describe the process? I could probably buy out Amazon's supply of solder and only be half way to owing the vw385 tools :roflmao:

EDIT: I found it (https://rennlist.com/forums/924-931-...xperience.html) but I guess I'm not 100% sure on the procedure. Also if you haven't moved I'm not too far away from you in Sterling Heights, MI! Though the cars are currently at my brothers place in the boonies (little south of Port Huron).

"Search function " is very interesting here. I searched last night and found two good threads started by Tifosiman. Today only one of them came up - using the same criteria. :rolleyes:

Here is the one that came up today. The thread you did find is quite good. Van's videos are excellent. :thumbup:
https://rennlist.com/forums/924-931-944-951-968-forum/152744-944-transmission-questions-for-the-experts.html

If you don't find specifically what you are looking for - pop back here with questions. No - I haven't moved, still in the location listed.

You are correct that there is a lot of hocus pocus and voodoo floating around with this transmission.
A certified tech with 10 years experience should be able to improvise and figure this out.

I was a self employed trans tech with base in General Motors Service Guild, successfully repaired just about every transmission known to man from 1960 era-presnt, heavy stuff like Allison, Case, all the way to precision auto including the entire German ZF line, Japanese PXBX, etc., etc.

I find nothing "special" about this transmission.

Been servicing these, as well as the diffs for 10-12 years on our own, and immediate circle of track friends transmissions and never had a failure.
Front running cars, rarely not on top step of podium.

If it's street and you want to achieve the correct "quiet running" accuracy, you can fashion improvised tooling to do so.

T

Two reasons: first is the hypoid pinion gear design, which is needed because the differential and pinion rotational axes are offset, in this case by 12 mm. When the axes are not offset, a spiral bevel pinion design is used and the ring and pinion teeth engage by sliding up and down the tooth flank, ie, from tip to root. With the hypoid design and offset axes, sliding also occurs heel-to-toe, that is in the radial direction with respect to the differential's rotational axis. This additional sliding puts a lot more stress on the pinion gear teeth, makes a lot more heat.

Second reason is that the eight-valve, normally-aspirated cars' pinions break frequently. This is because they are really mechanically marginal, and they don't get properly serviced. The critical dimension is the width of the pinion tooth at its root, because as essentially a lever arm, the root gets the greatest force applied to it. I've posted pictures in the past comparing the root widths of the 944 versions' pinion teeth. I did the math years ago on the tooth force, using Alec Stokes book as a reference, and the numbers were intimidating.

However, the good news is that you probably do not need to recalculate pinion depth and the necessary S3 shim. You do need to recalculate if any of the reasons listed in the WSM apply to you: different r&p set, different case, etc. You also need to recalc if:

• Someone has previously serviced the transmission and incorrectly shimmed S3. Yes, this happens.
• You have a 944S2 or 968, for which the factory made mistakes in production that, in the case of the 968, are well known.

I always measure, regardless, because I have the tools, most of my clients are racers, and I can do it quickly -- lots of practice. Where the above conditions don't occur, I rarely find that S3 changes.

You do need to measure and correct the S4 shim for the rear pinion shaft bearing. The need always changes. Turning torque is the only correct way to do this: the WSM's "recommended" measurement of free play is inaccurate and good only as a starting point. Range is 2 to 4 Nm, preferably at least 3 Nm. If you read literature from bearing manufacturers, you'll get the same basic guidance.

You're of course welcome to try bluing and reading patterns. I did, years ago. You'll find that the pattern is never centered because you are measuring the transmission unloaded. Put some torque through the transmission, things move and the pattern shifts. You'll also find that significant changes in the shimming (pinion or differential carrier), say 0.10 mm, do not give you reliable, discernible pattern shifts. If I were on a desert island without the factory tools, I think bluing would be worth a shot, better maybe than nothing. But it is far from accurate, despite lots of books and manuals that describe its use.

Good luck with the project!

@KevinGross

Thank you for your response! Work has been, well work... this week so I just got around to reading your reply. I have read through the WSM differential section a few times and have some ideas on how to measure and place the pinion in the "quite running" position. I only have time on weekends to get wrenching in so I'm not exactly sure when I'll get around to it but in the mean time I was wondering if I could get some measurements of the VW 385/1? From what I can tell the VW 385/17 magnetic disc is 5 mm thick (is it really 5 mm?) and the VW 385/15 dial gauge is set to 59.65 mm (Ro). So from the face of the pinion to the flat on the VW 385/1, if the quite running distance was 0.00 mm, you would have 59.65mm + 5 mm = 64.65mm. In order to get the distance of the pinion face to the ring gear center line, distance "E" in the WSM, I would like to know the diameter of the flat to the other side of the VW 385/1 ("a" in image) and it's overall diameter ("b" in image).

Thanks in advance.

https://cimg2.ibsrv.net/gimg/rennlis...d179d8007c.png

Hey Jason, dimension "a" measures to 30.50 mm, "b" to 32.00 mm. Good luck!

Thanks Kevin.

I'll try to update as I go and if I get really stuck I'll throw in the towel and just have one of the local shops that would have the tool setup the diff. Not so much out lack of effort / knowledge, mostly a lack of time.

Also figured I'd post the image below. Who said the engine couldn't come out from above?!?!? Didn't even remove the bellhousing as I wanted to tackle the (potentially) dreaded clutch fork pin and speed sensor bracket with all the room in the world. Only causality was the oil dip stick, which got caught between the master cylinder and one of the brake lines...

https://cimg6.ibsrv.net/gimg/rennlis...7046348545.png

Love the chain fall support😄👍

Yep when life gives you "reclaimed" lumber from your brothers home renovations and a Home Dept gift card you can do anything!!!

This picture is simply beautiful. Love it! Also, there's something really attractive about old straight rust-free cars that have paint worn down to the primer like that. So cool...