Dreaded automatic transmission Rattling question.

[Aowolf]

Hey guys and gals, I have an automatic 1988 924s. (the later motor) A few weeks ago my brother was driving the car home from work when it began to rattle at low RPM. At higher RPM though, the engine is smooth as silk. I took it to my Porsche mechanic who told me that the "Flex Cupeling" was worn out.

I know that isn't the official part name so Ill do my best to translate his mechanic speak. Basically he said there are two arms in the bell-housing that do not normally come into direct contact when the transmission is spinning. He told me that a piece of rubber sits between the two arms, and that it was gone now so that the arms are banging against each other at low RPM but are held together by centrical force at higher RPM.

Unfortunately Porsche sells the replacement rubber part for over $1100. What my mechanic suggested was welding the two arms together, but cautioned that to open the housing I would have to drop ether the engine or transmission.

Basically I am trying to figure out if there is a cheaper solution to the problem to stop the rattling. Will welding the arms work and is it healthy for the car? Is it ok to leave the rattle or will it have a destructive effect on the transmission?

[John_AZ]

Welcome and I have no idea what your mechanic means by "welding 2 steel arms together". Maybe he means the 2 tabs sticking out on the inner damper plate??
And welding to the outter frame plate???

This can only be a temporary solution at best and the cost to get at the automatic flex damper is at least 10-12 shop hours and beyond.

You can cross your fingers and go used on a damper. EBay or try Pelican used parts forum.
We have a good used parts member- www.944ecology.com.

Here is a PET diagram.



This is a new damper



GL
John_AZ
1988 924S + 1987 924S

[TibetanT]

No disrespect intended here, but, I would find another mechanic to do the work.

AND, buy a new part! Unless, like John has mentioned, you can find a used part from a very low mileage vehicle. If not, you will be right back at this point again very soon and P. O'ed that you didn't.

This is a very expensive, labor-intensive procedure so you want it done right the first time.

[Aowolf]

If I don't replace the damper right away will it cause damage to the transmission?

[John_AZ]

Originally Posted by Aowolf

If I don't replace the damper right away will it cause damage to the transmission?

Probably not to the transmission. How far from home do you expect to be towed when the flex disc finally distructs?

GL
John_AZ

[alantica]

Hello Aowolf. I am replacing the damper in my son's "88" 944 NA with a manual flywheel, pressure plate, clutch, and starting gear. This has been done before, but it is not a common practice. If you do the work and use the manual parts, your cost could be under $600.00. I'll send you a PM with my contact information. Give me a call and I'll explain the reasoning behind what we are doing.

In his 944, he started hearing a vibration centered near the middle of the dash. From the time he first started hearing it until the damper went out, he was able to drive about 250 miles. Luckily he was only about a mile away from my home when it happened. He started smelling a burnt rubber smell and heard a loud pop.

If your damper goes out, the car will not move. There is no damage to the transmission. The damper acts as a buffer between the flywheel and central tube / transmission. If you plan to continue driving it until it is fixed, make sure that you have a tow truck driver available 24/7.

We have done a lot of research and found there are few choices available when it comes to an automatic transmission. Just to get to the damper, the transmission has to be dropped, the central tube pulled back and dropped, and some other major parts. The cost for a mechanic for labor plus the cost of the damper is a major expense. An average estimate is $2,800.00 plus.

Do not let the mechanic weld anything as mentioned, especially if he is not a Porsche mechanic. The average life span of a new damper is 3-5 years. They tend to dry rot, so if you plan on getting a used damper, take that into consideration. I have a lot of information available for you about this job, just give me a call.

[alantica]

PM sent.

[Aowolf]

Thanks, Ill get back to you shortly

[silverstar]

Hello Alantica,

How did the swap of the rubber damper with the manual clutch + pressure plate work out?

Is there more vibration?

Did you also change the bell housing?

Thanks in advance.

[HondaDustR]

If you swap to a manual flywheel/clutch, you'll be able to just get used parts, since it will never have to engage or disengage smoothly, or have to last doing so. It will just sit in there permanantly clamped together. Just don't use an old rubber centered clutch disk, since they will disintegrate as well. Centerforce makes a much more reasonably priced disk than the OEM Sachs part that costs less than half the $$$. You may not even need the throwout bearing.

[galwaytt]

...with a 93 968 Tiptronic, I noticed driveline shunt on the overrun, after a day of fast driving.

I suspected the tranny, but my local erstwhile mechanic took one look, and pronounced 'doughnut' failure.

Pic of what came out, here: HERE

As you can see, there's nothing to weld...........

So, yep, when it goes, it well and truly goes. No damage though..........except to the wallet. My mech (and this was the first time he'd been under a Porsche) charged me Eur 900 for all work, and I supplied the doughnut.

Fwiw, my doughnut reached 145k miles and 15yrs old, so I don't subscribe to the every few years thing.

All my 0.02, as they say........

[alantica]

Silverstar - I haven't finished the swap yet. My son is driving on old Chevy Blazer. The last time he came home we completed everything up to dropping the tube. Hopefully we will be able to finish by the end of this month. I'll post everything once we complete the job.
.


galwaytt - keep in mind that a used part from a junk yard most likely has been sitting in the vehicle with no use. Just put this picture in your mind. Rubber disc sitting in an open area with exposure to humidity and heat and no rotation. A good example is a tire on a car in a junk yard for a period of time. Pull it off and you will find dry rot, especially here in the southern part of the U.S.A. I agree with you that a part in use that is not abused will last for a long time because the rubber is being flexed. Rubber that is not flexed will corrode. Even new rubber parts have a shelf life that is determined by the storage area, temperature and humidity. Location is the main factor. The 3 - 5 year time spanned as I mentioned above is from research in Atlanta, GA.

[silverstar]

Alantica,

Thank you for the reply and good luck with the venture.

Your results are eagerly awaited.

Regards

Silverstar

[galwaytt]

atlantica - I hear ya, as they say. With family in Norcross GA, I know what you mean about heat !

Like most things, and motorbikes are a classic example, prolonged non-use is worse than prolonged.........hooning !

[silverstar]

Since this thread has gone all quiet for now....

Here is something to get you sending all kind of flames my way.

But, but, but....

This is just exploring an idea that started with some mechanic suggesting welding as a solution......

Along the lines of swapping in a pressure plate + clutch: what would happen if a manual (spring-loaded) clutch disc (with the correct center spline dimensions) was inserted and welded to the outer steel ring that comes off the busted up rubber donut assembly. This assembly would then be bolted to the starter flywheel etc.

A competent machine shop should be able to get sufficient precision into the process of putting together the revised assembly at reasonable cost.

The only question then would be which clutch disc would do the trick.

Just a (crazy) idea... any comments?

[John_AZ]

Originally Posted by silverstar

.

But, but, but....

This is just exploring an idea that started with some mechanic suggesting welding as a solution.......

Just a (crazy) idea... any comments?

OR

Replacing auto flexplate with manual clutch parts

John_AZ

[Aowolf]

I (my mechanic) ened up swapping out the flex plate with parts a presureplate and clutch from a manual. Well I can't really speak to the mechanical side of things I know he did it with very little effort outside of getting to the bell housing. Drivability wise It added maybe 10pounds max to the car but feels just like it did when it had a working disk. It's been a few months so far and the car has been acting quite normal. Just thought I would chime in with the happy ending.

[John_AZ]

Fantastic!

Was the cost for the used FW, PP, disc? and labor a significant savings over just keeping the flex plate?
Did he use a rubber center disc to make the shifting smoother?

Thanks for the update.

John_AZ

[Aowolf]

The labor would have been almost identical from what I was told, I was given the FW by the mechanic but the PP was like $50 from a user here. Overall it was around $600 in labor and parts.

[John_AZ]

Again, amazing! The labor cost is half the normal flat rate clutch fee for 10 to 14 hours labor.
John_AZ