bambar

Hi again guys,

So gear shifts are generally very smooth.

When coasting at 6th gear, and pushing the throttle down a little bit, gear shifts to 5th smoothly. If I push the 'kickdown' all the way, shifts from 6th to 4th very smoothly.

However, whenever gear is at 5th and accelerating, downshift to 4th causes a huge jerk (almost as if somebody hit the car from the back).

This only happens when changing down from 5th to 4th at acceleration.

Is this the clutch slipping? What exactly is happening, and why only the 5th to 4th downshift? Car is a 955 Cayenne Turbo 2004.

Would appreciate any feedback.

davis391

Well, here it is, my inaugural post, and it's a question I can actually answer.

Based on my obsessive reading (mostly here) in the last months since acquiring a 2004 CS in October, the problem is most likely with the transmission valve body, and it needs to be replaced.

Seems that some just live with the issue for quite some time before getting around to repairing. I'm unclear on the long-term consequences of continuing to drive it as is. But when it happens, it does feel like the transmission has just joined you in the cabin.

See this thread for a bit of a primer: https://rennlist.com/forums/porsche-...placement.html

There's lots of threads here and elsewhere on this issue, which seems to present in 955 and 957 -- both models use an Aisin transmission, which is also used by the T-reg and the Q7 (don't know if current models of those two use an Aisin).

Based on my recollection, the DIY on this is more messy than complicated. If you were to have an indy do the repair, cost is around $1200 USD including parts.

Good luck!

phatz

read on
could be a fun experiment

bambar

Thanks nacnud..
Seems like a proper mission with a heavy cost. Will have to take some decisions!

bambar

This is interesting! Do you know if it works? Are these the same Valve Bodies you would find on a 955 Turbo?

It basically says "5-4 bump" - which is exactly my issue. In this scenario I would have to turn the K2 screw clockwise..

seankrider

My money is also on valve body - I have same year/model. Mine happened at or before 100k miles if I recall correctly.

Very doable DIY if you are inclined. I think I used Revmaxx upgraded valve bodies, at maybe $600-700 + returning the core from the bad one.

bambar

Thanks for sharing. Any reason you opted away from using alternatives such as the Transgo Kit?
Also, do you think what phatz posted above works?

seankrider

Honestly, I don't think I knew a self-rebuild was an option back then. Might not have done it anyway, if it requires special tools. Unbolt/bolt-on seemed pretty error-free on my part, and was maybe 1/3rd the cost at an Indy.

cgrupp81

I'm in major trouble now! Need advice. I had the same problem with my 2006 Cayenne S, with hard downshift 5 -4 and sometimes 4-3, but only when slightly accelerating uphill. (120k miles and bought it used a year ago.) Other than this annoying little distraction it has been great to drive. To try to resolve the thump, the first thing I just tried this week was a transmission refill kit from ECS Tuning, thinking simplest solution first. Reading the DIY procedure, I know my limitations and instead had a German car/VW/Audi repair shop who supposedly knew what they're doing take on the job. MISTAKE! Shop calls me and says, " Work is complete, but drive or reverse is just like neutral. Might need a new tranny." The shop tried to check codes, reset codes, etc. for a day and a half but they were clearly over their heads. I ended up towing the car back yesterday on a flatbed (and now with engine light on). So now the transmission wont engage at all. It's in my driveway now...dead. Help?

jeanmarcboilard

They likely didn’t put enough fluid in.

phatz

Dont fear.

I agree 100%, not enough fluid.

Note: you need a valve body ...not the fluid swap.

Did you pay for this privilege? ...get your money back!
If they refuse dispute the charge (hopefully you used a credit card)

Should you insist on just the fluid, if an independant shop:
How will you know if they know what they are doing?
..when you query the tech that will be working on your vehicle, she / he, will be able to tell you the temperature at which no more fluid can be added off of the top their head

If I recall the engine light will come on in this situation of attempting to drive with low fluid

cgrupp81

Thanks for your advice, guys. On the fluid question, I purchased 10 Qts. of Redline D4 ATF as recommended in the ECS Tuning kit instructions. The fluid change took 9 of the 10 Qts. I am talking with the tomorrow about the refund, and temperature that he used. Funny thing is that he is a VW, Audi tech and this procedure should be familiar from doing a Toureg or the Q7 I would imagine. He said he knew the procedure. I think I will start looking for a rebuilt Valve Body and if anyone has a good source there I would appreciate it. Then planning on doing it all together in one shot at a more reputable Porsche specialist.

jeff spahn

Get a durametric kit, get a Revmaxx rebuilt valve body. Get 11 qts (in case you spill some) of Royal Purple Max ATF. Get a filter and gasket. In three hours (if you are really, really slow), you'll have a new feeling car.
It's a super, duper easy job to do. Just follow the Pelican Parts tutorial and you'll have no problems. Seriously, my 12 year old could do this job.

AO

+1
Exact same experience. I tried to rebuild it myself with a shift kit, but that was a disaster. Just get the RevMax rebuilt VB and like Jeff said, in about 3 hours (albeit a bit messy) your car will feel buttery smooth. I opted for the Mobil 1 fluid, but whatever. Just be sure to lube the o-ring for the filter. If that filter doesn't seal you will have issues. If you can do brakes, you can do this.

jeff spahn

What Andrew said about the O-ring. It's big so its easy to see. Just look at the Pelican article, it's all there.