evozine

Car: 1984 Porsche 928 / Automatic Trans.

Problem: When driving the car at medium to low rpm's the car simply slips from the forward driving gear into neutral.

I've heard that checking the trans. fluid is the first step, beyond that, does anyone have direct experience with this specific problem. One fairly knowledgeable mechanic believed that the problem is not with the vacum system.

Any thoughts..

Al

Schocki

Check the shifter cable to the tranny, adjust it according to the WSM.

Mrmerlin

does it slip out of gear with the selector in the gear under D ? You might need to readjust the shifter cable, Also check the fluid level

evozine

The car drove fine for 10 minutes, then, I was in drive at around 2,200 rpm, and the car just shifted to neutral. I dropped it down to the next drive gear, and it shiftd to neutral again.

Thanks for the free advice. I need all the help I can get. I am planning on re-inspecting and re-test driving this car on Monday with a Porsche guy. If I think it can be fixed without rebuilding the transmission I may buy it, as the body and interior are near perfect; the engine is also smooth....

thanks,

AL

Mrmerlin

is the fluid level correct??

evozine

UPDATE:
Well, I bought the car today: http://www.evozine.com/porsche/

Even with the automatic trans problem, the body is nearly perfect, and so is the interior, wheels, engine, brakes, etc. Here are the symptoms after one day of ownership:

When I got in home, I noticed that the fluid container looked empty from the outside, I will get under there when I have more time and fill it to the appropriate level. The car drives perfectly in third gear, and shifts from first to third without any problems. The only problem occurs when I attempt to drive in using "D" gear. The car starts out fine for a few minutes, but then slips to neutral, especially when going up or down hills.

I've gotten some great advice thus far, (i) check and fill fluid, (ii) adjust trans cable, (iii) check vacum system. I will try all of these first...

Mrmerlin

before you add fluid open the cap and stick your finger in to take a sample , smell the fluid if it smells burned , Stop get a trans filter and pan seal and 9 qts of dextron 3 and change the fluid.
Empty the pan first and then turn the engine to top dead center and the drain plug for the torque converter should be lined up with the opening on the bottom of the trans axle drain this as well. refit the plug and install the new filter and pan gasket the bolts are not to be tightened very much as you will crush and damage the new seal the WSM gives the correct torque IIRC its 8 to 10 ft/lbs.
If the fluid smells OK IE not burned add fluid to the lines on the side of thank, you may have to clean the outside of the tank to find the level after you fill the tank start the car and run the trans shifter through every selction, and check the level with the car running in park and the E brake ON, make sure your on a flat surface, you may have to add more fluid, I hope that you dont have a leaking transmission as this usually indicates a bad torque converter seal or the front pump O ring needs to the be replaced usually both

evozine

MrMerlin,

I took a 20 minute drive last night, I then checked the fluid level and smell per your instructions. The fluid level is correct, but the trans fluid did indeed smell burnt.

I picked up the OEM filter and pan seal. The goal this weekend is to change trans fluid, seal and filter, then adjust shift lever.

If this doesn't solve the problem I'll have to ask the other poster who has a spare 4 speed in automatic in his garage for a great deal, as I am not up rebuilding a trans my garage...

Thanks for the clear advice..,

soontobered84

I don't think there is a way to drain the tranny and change the filter in one's garage without getting at least some ATF on you while under the car. LOL

evozine

Ok, Just a few comments and picts regarding my tranny fluid, filter and seal replacement today on my newly acquired 84 automatic.
Thanks to member MrGST for spending his Sunday helping me with this...

Statements:
-Doing simple maintenance on my 928's was much easier than I thought.
-I thought the slowest/hardest part would be the actuall filling of the tran fluid into the resevoir, (MrGST had the idea to use
gravity and 5 feet of Home Depot clear tubing) but it quite fast/easy.
-I didn't realize just how low the car sat until needed to work under it.
-The car shifts more smoothly now, but the change did not solve the problem I'm having with 4th gear, so for now I
am going to drive it without 4th, the manual says you can do this up to 90 miles per hour.

Pictures: (i) car on jacks, (ii) Trans pan off (looked quite clean),
(iii) Lined up TQ, (iv) tranfill 1, (v) transfill 2 .

MrGST

Glad I could help out. Besides, what better way to spend a Sunday than working on a cool German car?!

Mrmerlin

thats a nice big garage 3 car??, great idea on the filling tube, the torque converter looks new no rust so you trans may have had work done on recently, Steve Cattano will be better diagnose the trans loosing a gear

Brian Felts

Mine was doing the same thing...........Tranny Fluid change and it was back to perfect EXCEPT the gasket split last week and now I am redoing it again and using the updated pan gasket.

See this thread for the part ###

https://rennlist.com/forums/928-forum/412617-trans-pan-gasket-failed.html


Brian

Bill Ball

Just for giggles, add some trans cleaner. No particular brand, but stuff to add that cleans varnish, etc. It can free up valves and can resolve some shifting problems - worked for me in a no-first-gear situation.

evozine

Thanks Bill, the first gear on my car appears to be working now. I floored the engine from a stop and definately engaged first gear, and chirped the wheels...!

I'll try some tranny cleaner this weekend- perhaps that will fix my 4th gear, which won't engage at all. Does anyone know if 4th gear on a 84 auto transmission is serviceable from under the car...?

MrMerlin,
Yes, the garage is a three car, but I've gotten four cars in there, it all depends on how small the cars are, perhaps I could get four sharks in there. The benz now sits in the driveway...