tifosiman

OK, since I grenaded my transmission this past weekend, and now suddenly need to make a decision on what I am going to do for a new one, I've been pondering the following questions:

1. How hard is it to replace the ring and pinion gears in an otherwise good transmission? Could I do this myself, or would I be better off having a transmission shop do the work (probably a redundant question).

2. Is the ring and pinion gear different/stronger on a turbo trans (I would hope so), and can these be interchanged into a late 944 trans?

3. If the answer to question #1 makes me think that I can do it myself, it looks like while it is all apart, it would make sense to go ahead and put a quaife LSD in there since it would be apart anyway. Possible for me to do?

If anyone has any comments on this, it would be much appreciated. I know the rest of the trans from the r&p back is still good, and sealed, so that none of the shards from the pinion gear got back into the gears.

Additionally, I may need to buy a transmission as a stop-gap until I work all of the above out. Anyone have any idea what a un-rebuilt late 944 5-speed trans with 113K miles is worth? How much should I offer for that (it's not from a business, it's from an individual)? I found some 951 transmissions in the classifieds, but nothing comparable.

Thanks in advance,

Jeremy

xsboost90

well i aint no expert but i done some work on dem der porshas and i would just put ya one of dem ten bolt posi's out of a camaro i der and youll have no problems.......

I know that a quaffe is very expensive..$1200.00??? and to do the install you would need the proper shims and excess to a press to press the bearings in and out until it is shimmed properly. Oh, and you also need the $1000.00 torque "wrench" to check the torque/lash after you shim ea. time. What about adding a trans cooler to an n/a trans to keep the temps down?

tifosiman

Nevermind, post deleted.

xsboost90

well the only way to get a really good transmission is to take - say your old unit- to a race shop that knows what they are doing and have some quality parts installed. I would ask andy for that core back and send it out or at least price out getting a quality trans built. The turbo/s units are geared wrong and the others as far as i know arent any stronger, lsd or not. I would say try to put a trans cooler on this trans and baby it out of the hole cus first/second seems to be when these get destroyed. Besides, the money you spend on the trans would have just been labor for any shop. If you decide to remove that one let me know i may buy it for a spare for the "race car".

tifosiman

Right on. I guess I just need to figure out a fair price for both of us, knowing that I will probably be replacing this one in the near future.

tifosiman

OK, does a trans cooler from a 951/S2 tranny bolt onto a late 944 trans with the proper parts? I've never seen one on anything other than a 951/S2 trans.

Scott at Team Harco

Tifo,

I rebuilt my transaxle a few years ago. It is not beyond the realm of possibilty for mechanically inclined individuals.

You might want to search on my name to see if you can find the short novel I wrote on it a year or two ago. I'll be here to help you as needed, too.

The basics you need include the following:
A good shop press
Various snap ring pliers
An oven
Pullers
Lots of patience

Follow the service manual carefully and take your time. Read and understand every step. Stay a few steps ahead in the manual at all times to anticipate tool or part needs.

You're obviously going to need a new ring & pinion. I got mine at Vertex. You probably have a better source. Make sure they are matched to each other. You'll need to disassemble quite a bit to get the pinion out. Pull all the gears and stuff off the pinion shaft (per the manual). The diff will basically come right out. The ring gear bolts to the diff. If you are going to a new unit (Quaiffe for example) you just need to bolt the new ring gear to it. There should be tongued washers to retain the bolts - these should be replaced with new parts.

Inspect all bearings to see if they need replacement. Obviously, the more bearings to be replaced the more work involved. Now comes the fun part. Getting the bearing pre-load and gear lash correct. You don't need the fancy tools listed in the manual. What you really need is a good assortment of shims, a tube of zinc oxide (the stuff lifeguards put on their noses) and, hopefully, an experienced hand with a feel for rotational forces within a gearbox.

You can get a reasonable estimate on the shim sizes by squashing solder between the bearing races and the housings. Measure the thickness of the crushed solder after removing everything to get at it again. Based on this measurement it is possible to estimate the required shim to give the desired preload (or end play). By juggling shims from one end of a shaft to the other (either side of the diff bearings too) you will move the ring and pinion in or out as needed to get the proper gear mesh (use the zinc oxide to read the "footprint") and the shim thickness will define the bearing preload. This is the part that takes a lot of trial and error to get right. Once you do get everything correct seal the case with Loctite orange. I'll double check the number.

It's clearly not as simple as this - but it is not that difficult. As I say, with the right tools and lots of patience, it can be done. Lucky for you, there seem to be lots of good Rennlisters in your area to lend a hand.

Best of luck - we're all in this one together. Let me know if there is anything I can help with (from Michigan, anyway).

kasturbo

If all you are doing is autocross then I wouldn't worry about the trans cooler. The runs are so short and at such low speeds it won't make a differance. Quality fluid will do just fine to resist heat if your even getting the thing that hot. If you were doing multiple track events a year then I would do it.

tifosiman

Thanks Scott and Kevin for your input.

Kevin, I was afraid you would say that.

Scott, that does sound complicated, but not overly. Where does the oven come into play?

xsboost90

i think its a heat the case, freeze the bearings to fit together kind of thing. expansion and contraction.

Scott at Team Harco

According to the manual - there are a number of gears, bearings, etc that should be heated before installing. The manual tells you what temperature to heat to. Gets a little dicey holding the pinion shaft and then pressing on the hot gears - it's best to have a spare set of hands.

Waterguy

You have one option to get a stronger transmission with similar gearing: a 944S2 tranny. However, given the limited number of S2s made, they must carry a premium price. Check Danno's site for more information on gear ratios and transmission codes.

Dal Heger

The S2 and the turbo transmissions are MUCH more stout than the base 944 transmissions. I have not heard of any ring and pinion problems with either the S2 transaxles or the turbo transaxles, and this is with cars putting down over 350 rwhp! The R&P on these cars was beefed up substantially to cope with more power.

The best transaxle to get if you want more power is the turbo S transaxles. In addition to having all the options (limited slip and oil cooler) they have stronger 1st and 2nd gears (heat treated and shot peened for strength).

Just FYI.

Dal.

kasturbo

Were these autocross cars? I went through two turbo ring and pinions in two years of autocrossing. Either way, a turbo tranny would not work for Jeremy. The gearing would be way off for the NA. It would be like autocrossing with a ton of turbo lag in a to turbo car.

If you could find an S or S2, I think you would be fine. Also call Powerhaus for the ring and pinion and for other options. Website is www.powerhausII.com. They do rebuilds, but can also tell you about how to make the r&p stronger.

tifosiman

OK, thanks for all of the input.

So, a 944S trans has a stouter r&p than a statndard 944 trans? Is it the same r&p as an S2 then? This is why I am asking:

The previous owner of my car destroyed the trasnmission at around 70K miles. He bought a used transmission (with unknown mileage) and had it installed. I bought the car at 72K miles a few months later. By 76K miles, the r&p blew up on that trans. When I was having that transmission replaced (I didn't feel comfortable doing it myself back then), my mechanic commented to me that the dead trans he removed was an S2 unit.