Porschenut_Lee

Hi all,

Lets get the details out of the way:

1984 Carrera Targa
88,000 miles
No major rebuilds ever done on engine or tranny.
Engine runs beautifully, tranny is slowly getting worse.

1st to 2nd shift is awful, and really kills the fun when trying to accelerate hard. 3rd is becomming increasingly difficult to put in and out of gear. Grinding when 5th to 4th, and into reverse if I don't slide into 1st gear beforehand to align.

I have seen a lot of posts concerning the difficulty of a 915 rebuild. Some feel that it isn't that bad, others feel that it is better left to a pro. My problem is that I am not a pro, actually have never seen a tranny torn a part. I am mechanically inclined, have done several complete suspension, brake, steering component rebuilds, etc, but have never been involved with tranny work.

1. Am I crazy to attempt this? How difficult is the rebuild?

2. If I am saving the cost of the labor to do the rebuild, I would like to go ahead and replace all synchros, dogteeth, sliders, etc.
Where can I buy all of the components I need includng the above mentioned, gaskets, etc as a package deal so that i don't kill the wallet purchasing seperately?

3. Is there a good reference that I should have handy when I do the job, and possibly read from cover to cover prior to attempting?

4. Specialty tools required?

5. How long can I expect the car to be "out sick" while doctor nutcase attempts the rebuild himself (assuming that I am doctor nutcase of course)?

I want to learn to do every aspect of repair on these cars. It drives me crazy to not know how to work on my car, and as a relatively new owner I have a lot of leraning to do. This would not only be a good start, but a hell of a bonding experience with the car. I'm sure I would have alot more respect for the trannsmission afterwards.

Any input or advice would be great from those with previous experience.

Thank in advance,

Lee

lally911

You can do it. I just did and had never seen inside a tranny before. Total bill was about $1400 for all new synchros and brake band parts, new dog teeth for first and second, new 1st/2nd slider, and 1st/2nd spider gear. I used various sources but found this link to be the most helpful

http://www.pelicanparts.com/motorcit...nnyrebuild.htm

Take lots of pictures of everything as you go along to help you get it back together. Its intimidating at first but by the time you have the gear stacks out it doesn't seem nearly as complicated.

Good luck with it!

Keith

Peter Zimmermann

Lee: There's a tremendous amount of knowledge & expertise involved with correctly rebuilding a 915 transmission. I've done them after they were done by others, believe me, if you're not technically astute, and own the $3500 worth of special tools needed, your trans will (probably) not work properly when it's done. I'm not going to insult DIYers here (I'm quite sure that there are a few who could do a wonderful job), but a 915 transmission might not be the best place to start. Sure, at your low mileage I'm sure that you won't encounter ring & pinion difficulty - unless at one point your car was driven extremely hard following cold starts. If that's the case you will discover that your rear pinion bearing outer race will be loose in the housing, which will require diff breakdown to repair. When the case is fixed it's always good to re-set the R&P after. Everything about transmissions is assembly sequence, everything must be kept in order, the bushings and bearings for the 5 forward speeds must NOT be mixed up, etc. By the way, reverse is not synchronized, gear grind is always driver technique unless you have a clutch or linkage problem. First to second shifts should never be made quickly, or above 4,000 revs - you are not driving a Mustang! 915 transmissions were never designed for speedy off the line performance, but turn them loose on a race track and there are few transmissions that are better. Your 5 to 4 shift is probably linkage, and you're probably nicking reverse. I would strongly suggest reading a factory manual before attempting the job. By the way, those 915s that I mentioned that I was fixing after somebody else did them, some came from other shops! If you choose to have a "pro" do the work at least get some references, ask to see their tools (I did not consider this an insult when approached in this manner by a customer!), and find out if they know how to fix that loose bearing race - you won't find that in any manuals! You might start getting your feet wet by finding a pro, and then asking them if they will let you remove the trans from your car yourself. Doing the R & I might be a good start for you...

Regarding parts purchase, you have to shop just about every piece. Some are only available at the dealer, some are available aftermarket, but cost more than at the dealer, etc. You might find a "package," but because every trans has a different repair requirement it will be impossible to know what to buy until the trans is apart & diagnosed.
Pete

Porschenut_Lee

Keith, thank you for the encouraging reply, the link you pointed me to looks to be an outstanding resource. How did your rebuild turn out?


Pete, I appreciate your straight forward honesty. Your opinions are very well respected on this forum, and for good reason. After reading your reply several times I am not so certain that my transmission is in need of a rebuild just yet.

I recently had the car in the shop for a valve adjustment (valves actually sound louder now than before but thats another subject) and a corner balance and alignment. While the car was in the shop, the clutch cable was adjusted per factory spec. The grinding does not seem to be very consistent, and only happens 50% of the time. Occasionaly when starting the car in neutral and trying to slide the shifter into first gear I will grind also. There are times also that I cannot get the car into reverse with the motor not running. Perhaps you are correct in stating that I may have a linkage problem. Does the additional info above correspond with what may be encountered with linkage issues? If so, where do I start? As stated before, I am clueless as to tranny/linkage/etc. operation, but am willing to learn.

Also, I may have mis-understood what you were saying about not making 1-2 shifts above 4000 rpm. The peak horsepower is somewhere around 5800 rpm, and in order to take advantage of that power one would have to make the shift over 4000 rpm. I couldn't imagine never seeing over 4000 rpm in first gear. That is where the car seems to shine. Am I reading this wrong? It just seems funny to me that Porsche would install a transmission in a sports car that isn't designed to see close to redline in first gear.

I guess I have more to learn about these fine machines than I had imagined. That is the beauty of Rennlist. Keith and Pete, thank you both for sharing your knowledge.

-Lee
1984 Carrera Targa - Slate Blue Metallic

lally911

My rebuild turned out just as I had hoped - all gears now shift fine with no grinding. The rebuild, plus a Wevo shifter and coupler, makes for a nice shifting 915.

My problems were similar to yours - grinding in to first, tough 1st to 2nd, and starting to have problems going in to 3rd. From the symptoms you describe it sounds like normal wear items need to be replaced in the gear stacks - synchros, slider gears, and dog teeth at a minimum. You won't really know until you get it apart and can visually inspect. The special tools I used were a hydraulic press which I'm lucky to have in the garage and I purchased the dog teeth removal tools from Pelican. A clutch alignment tool will probably be needed when you put the whole thing back together. Other than that, its normal shop tools. An air compressor and impact wrench are good for the big nut on the end of the gear stack.

For replacing the normal wear items you don't need to get in to the ring and pinion which is where some precise measuring equipment is needed. There are plenty of excellent threads to help you out and folks on rennlist and pelican are always willing to help out. Like you, I want to learn how to do just about everything on my car and this task really gives you good experience. Dropping the engine and tranny is quite a learning experience in itself. Now I know exactly what is happening every time I move the shift lever.

Regarding parts, I purchased all necessary parts through pelican and have a spreadsheet of all the part numbers if you need it. Check out this thread if you have time. Its long but is from a guy who didn't even know what his sway bars were and he, with a lot of great assistance, goes through his own successful tranny rebuild. Pretty cool.

http://forums.pelicanparts.com/showt...hreadid=159059

Peter Zimmermann

Lee: I've owned and driven 911s almost daily since 1971. During that time I've drawn many conclusions regarding how to drive them, from first gear usage to doing turn 8 at Willow Springs Raceway flat out in 5th. Others might disagree, but it is my belief that the good Doctor (Porsche) never intended his cars for drag racing type use, supported by the fact that they are too fragile in some areas (i.e. 915 synchros and other items!). 911s shine, when well-driven, in high speed applications, and even slaloms. Speaking of slaloms, you'll probably never compete in one where first gear is required, other than at the start. That's why I never ran slaloms, because part of the timed lap was first gear acceleration. I found autoxs, where consecutive laps are done, usually all in second and third gear, to be far more fun. The beauty of a 911 is entering a Drivers Education event, sponsored by a group that favors Porsches, and going home at the end of the day thinking that you may have just learned how to do one corner near your car's limit. If you learned two corners you're way ahead of the game!

Now, shifting. This ties into what's been posted so far. I believe that every first or reverse shift, following starting the engine, should be done by slipping your gear lever into the gear that works the smoothest on your particular car. My '82 likes to be put into second, prior to selecting either first or reverse, and I have never crunched either gear. Remember, unlike a Mustang where the shift lever goes straight into the top of the trans, your 911 has many feet of linkage between your shift lever and the gearbox - you must allow for that. Regarding clutch/valve adjustment, I don't like hearing that your car came back with louder valves than before it went in. That makes you wonder if they couldn't do that, why would they do the clutch cable correctly. There is much to know about clutch cable replacement and adjustment for the cable on your car. At my shop it was rare to get a first time in car on the hoist and find that the existing cable had been correctly adjusted. The shift linkage must also be set correctly, and can have problems at the shift tower/lever, or the coupler inside the rear of the center tunnel. I think that the first thing you should do is to spend a week using my cold start shifting method and see how much your driving experience improves. Two things to consider: (1) You must adjust to your car - your car will not adjust to you, and (2) Don't fix it if it ain't broke!

If you have a chance please read pages 28 - 31 im my book, The Used 911 Story - 8th edition. The chapter is a discussion of the 915 component of this, your, thread.
Pete