What is the "CWP"?
What is the "crown wheel gear"?
Now you know the extent of what I don't know about these trannies.

By "indexing the cwp" I mean checking the pinion depth and carrier preload then adjusting until within spec.

So what other damage may need repair?
The mechanic that inspected this 915 found nothing wrong, and I told him exactly what I had done and what you fellas on the board thought was the problem. He found a loose pinion bearing race, nothing more. What are we looking for?

So is this tranny trashed? Soon it will not be economically feasible to throw more money at this given that good used 915s go for ~$1000.

My 5c.


1. You dump the clutch on drag-strip with your 930 engine and 915 box.
2. Wheels hook up, lot's of torque is transmitted and plate that holds pinion bearing race is distorted by high radial loads from pinion, allowing pinion bearing to get loose. Pinion moves from it's original position and R&P backlash goes out of whack.
3. You drive home with whining tranny, pinion establishes new wear pattern with crown gear.
4. You open the tranny and glue back old pinion race into already worn/distorted plate, w/o checking backlash and probably into different position than it was before.
5. You add reinforced side-plate and bearing carrier (but pinion bearing is still in it's OEM glued wall?) but tranny still whines.

Possible reasons of residual whine:

1. R&P backlash is still out of whack, you glued back the bearing but it only got fixed to it's new position.
2. New wear pattern is established since strip-incident and R&P will continue to whine untill they gradually wear ino each other (might take a lot of time).
3. Pinion went trough plastic deformation due to extensive torque (sounds unlikely, as those parts are hardened and usually just break instead of warping).

My guess is that you have mixture of 70% 1 and 30% 2.

Your options:

1. Take down the tranny. Open it. Check if pinion bearing is still fixed to the plate. Have a expirienced gearbox technician re-index R&P backlash by the book (checking wear pattern with indexing colour and all other things that are to be done). Pinion might still whine for a while as "somebody else was wearing your shoes". Baby your tranny further on.

2. Drive it as it is. Whine will probably get quieter as parts wear into it's new position. It might develop lot's of play in R&P as material is worn down. Baby your tranny further on.

3. Do everything in 1. but change R&P to used items. Cost prohibitive. Baby your tranny further on.

4. Throw out whole gearbox and replace it with 930 transmission and Carrera halfshafts. This was probably the cheapest option before you opted for fixing your existing tranny. Short 930 transmissions cost more though. Never worry about drivetrain anymore.

5. Remove tranny and install 5-speed G50. Requires coilovers, some metalwork and new shifter. Pricey but clearly the best option. Never worry about drivetrain anymore.

6. Buy a used 915 transmission, move WEVO side-plate to it, sell your old one as rebuildable core. Cheapest way of getting rid of whine. Baby your tranny further on.

Thank you Goran - actual options and advice are exactly what I am looking for.

I want to add, for the record, that I NEVER dumped the clutch on this tranny. I like speed but I'm not an idiot. The clutch was completely let out and then the throttle stomped through the floor. The resulting violent tire shake got me.

I like option #4 best but have not found a short box 930 for under $2500. I'm always looking.

Please elaborate on option #2. I was lead to beleive that if I continue to drive my car it will destroy the Ring Gear. Not true?

Something to add to the mix -- I have in my possesion a used 915 with the same exact problem that my current tranny suffers from - only worse. The Ring Gear on that tranny is visibly worn to a sharpness on each tooth. (My Ring Gear has NO detectible wear). Can I put this trashed Ring Gear in my current tranny or is this not possible due to the R&P being a matched set?

I'm looking for options here TO BUY ME TIME. I need to drive the car for probably another year while looking for a short bellhousing 930 tranny. I don't want to ruin my current R&P, they look perfect.

HI you need to find a guy with a tool VW 385, or P258 the old tool with addapters, and some one into porsche or VW trani's to check the depth on the pinion, you say you put a new side plate on , was that when the CWP was set or after??? if it was after the bearing pre'load should have been re checked and the back lash, you will require a set of shims for the clamp plate and the diff bearings to adjust correctly, is the noise there constantly both on and off the gas/throttle?? or just on the throttle

regards mike

Without blueing the gears and looking at the contact patch, you can't really say for sure if there is abnormable wear. It doesn't take much to make noise and it's not necessarily visible to the 'naked' eye.

I found a mechanic with the proper tools to check my R&P. Will find out today if he is willing to do it for me. If not, a friend and I will attempt it ourselves using the old hotrod method of measuring the contact patch and adjusting until perfect.

The reinforced sideplate was added after the incident, no shim adjustments were made. If you look at 10 of these trannies and count the carrier bearing shims on all 10 you will see they are the same. My mechanic did just that. These trannies were mass produced so all the parts except the R&P should be interchangable with little or no adjustment needed.

HI i am sorry but the 10 trannies you have did not come from the factory, or your mechanic must have built them as the shims for the pinion and the diff bearings are all diffrent sizes , pinion from 0.10-0.20, the diff bearing shims are from 2.4-3.7mm in 0.10 mm size's,
AS you added the side plate after the incident the bearing preload will be wrong and if to tight will push the CW in to the pinion and the diff will whine and whine. I asume you have a MM micrometer 0-25 to check the shim size. set the bearing pre load and then set the back lash,
good luck
regards mike

There is a normal amount of variation in machining during manufacturing that must be accounted for in the assembly process.
Manufacturers have to vary the shimming by a few thousands of an inch to obtain the proper stack-up. Each transaxle will have a little different shim pack as a result.
The typical mechanic doesn't understand or chooses to ignore this fact.

Another option would be a shortened G50. You won't need to go to coilovers that way. Lister "Dean" (a frugal Yankee) would be a good source to ask on how to do it the most economically.
-Chris

G50 would be great but too much hastle and $$$.

All the old trannies had the same number of carrier bearing shims - 1.
Now if that one shim was diffent thicknesses I do not know. The assumption was that they made one size and stacked them, guess I was wrong about that.

I'm calling the mechanic with the set-up tool today. I'll let you all know if it's a go.

You will find the shim sizes and part numbers about 2/3 through page 1 of this thread. My post was dated 10/30/05.
915 Repair - What tools needed to change carrier bearings?


Who is your mechanic? I’ll be glad to call him on my nickel and help.

It might be useful to print a hardcopy if all these threads and give it to him.

Best,
Grady

Thanks Grady. Jim Williams has agreed to look at this for me. He has the tool but has never used it. It will be a learning experience for us both.

I have another 915 with identical damage that was allowed to wear out the R&P. The plan is to purchase a good used R&P from someone here on the board and replace the damaged R&P in that tranny. We will then index the "new" R&P and order the shims needed. Hopefully we can learn how to do this properly on the damaged tranny first, before I take out the good one (that was fully rebuilt 4 years ago) in my car and do the set-up on it.

How much should I expect to pay for a good used R&P?

You silly crochety old bastard:p

Please e-mail me Jim’s contact info. It will be my pleasure to pass on what little I know. With your good photography and everyone’s input, this could be the definitive thread on 915 R&P (CWP) set-up. I may buy a similar 915 and proceed in parallel, health permitting. I have all the tools also but would be very slow.

It would be nice to know your name.

Best,
Grady
gradyclay@hotmail.com

My name is Brian, thank you very much.
I'll tell Jim to check out this thread. He seems exited to learn this procedure. I can't imagine owning a $2,500 tool and never using it, I'm lucky to have a set of screwdrivers.

Checking in.........
 

Grady,

I've been following the thread for a couple of days so I thought I'd go ahead and join in. Feel free to contact me, I'm sure you will bring a lot to the table (read workbench).

Brian,

Excited would be me learning I'd won the 911 Club Coupe.:) But I am interested in doing a R&P adjustment. (BTW, the Fairbanks pinion measurement tool was just under $2500, by about $1800.) I spoke with Gary on the phone yesterday to verify the setup procedure for using the tool.

Jim,

Great!

Tell me about “the Fairbanks pinion measurement tool.” Is there an internet link or can I talk to Gary? If this is an inexpensive suitable substitute for the NLA P258 and VW385 then great!

Do you have the Porsche Factory Workshop Manual? Other?

As I noted in this and the linked posts, there are three basic Factory procedures:
1) Measuring the axial position of the pinion.
2) Measuring the pre-load on the differential bearings.
3) Measuring the backlash between the pinion gear and the ring gear.

Of course there is the non-Factory proceedure of inspecting the contact pattern.


Jim, you will find that I repeat myself and go into excruciating detail. Please don’t be offended – it’s not for you. These archived Forums will outlive all of us. We are speaking to someone in 2106 and later. One of the real benefits of this Pelican Forum is it is self correcting. If I post something unclear or in error, someone will catch it and a correction can be made.

The goal here is twofold. First is to repair Brian’s transmission. Actually more important is to document a very difficult situation and instructions for recovery. Repairs with all new parts are easy but not economical, or possible with many NLA. Arguing the subtle differences will be of great benefit to everyone.

What are your address, phone, fax and e-mail? Mine is posted above (I don’t use PM on any of the forums). If you need some technical info, perhaps I or others can send it to you and Brian.

Best,
Grady
gradyclay@hotmail.com

Sorry if this is a silly question...
Does the R&P position change over time such that if you were using a used R&P you would want to duplicate the "as run" settings in order to get quiet operation?
-Chris

Chris,

Good question.

I think this is a major part of the overall question with Brian’s issue. We all know that we can take the set of Factory new parts and build a 915 transmission just like Porsche did when new. The difficulty is with a used, run-in Ring & Pinion gear pair (R&P). This is further complicated with transmission case issues and bearing wear among other.

I think our first mission is to help Jim get Brian’s 915 repaired the best reasonable. I think the higher mission is to analyze all the issues and develop a proper (best compromise) procedure for used 915 R&P set-up.

I think our first task is to allow everyone to identify a defective R&P. Many times this isn’t obvious to someone looking at one for the first time. There are many clues. Attempting to set-up a defective R&P is a waste of time and money. Who has good images of the defects?

Best,
Grady

BTW, Chris is one of several who have given me Porsche workshop manuals. Thanks again Chris. This thread may be equally applicable to the 930 transmission.
G.

I've got a set of 930 and 911 SC manuals but they do not go into the detail that you have in these threads.
Your assesment of the situation is spot-on. Used equipment may have issues that do not apply to new equipment. My 915 was built in 1978. Fortunately I purchased the 78,000 mi car from the original owner in 1996 so the history is known. I had the tranny rebuilt in 2002 before installing the 930 engine, normal stuff like synchros and dogteeth. A lot happens to normal wear components in 28 years.
Jim I'm glad to hear your tool cost less than the factory unit. That is a staggering price for a rarely used tool (maybe that is why it is rarely used).
Anyhow the hunt is on for a good used R&P. I've got a couple of leads now.
I must lead a boring life, I AM excited to see this work!