1989porsche928

Hello, I took my 1989 928 with a automatic transmission to the mechanic the other day. The vehicle would not shift out of second gear. I told him I only wanted a diagnosis. So far he told me the transmission fluid was low, darker in color and smelled burnt. Is this a sign of the transmission being ruined? I am waiting for some estimates for a flush / filter change and to just swap the transmission out with a rebuilt one.

dcrasta

Do not 'flush'

Drain the fluid from the convertor and from the pan (rotate the engine with the crank bolt until the drain plug for the converter is pointing down.

Purchase a filter kit (roger or Pelican have them, along with other supporting vendors)

The filter kit should include a new gasket, a filter, and two sealing rings/washers.

Remove the filter, inspect the valve body (there is a spring that can dislodge, make sure it is in place).

clean everything, replace the filter (make sure the pan is torqued correctly and I would use a little blue loctite).

Refill the Fluid: Fluid has to be topped off with the motor running (I put it in reverse with the parking brake set on the lift).

These transmissions can take a load of abuse before 'failing' . Flushing is a fallicy and requires them to disconnect the transmission lines and run a pump / reservoir . I do not recommend flushing. I recommend draining and replacing the fluid as recommended by the FSM.

BTW The FSM recommends a service interval of about 30k for the filter/fluid replacement.

THis can be done on jackstands however access to a lift makes it easy.

1989porsche928

Thanks dcrasta, I will tell them not to flush it when he calls back.

Landseer

The 89 automatic is the best of the breed due to valve body mods and rear gearing.
Don't let it get separated from your hands.

1989porsche928

This guy seems kind of seems like hes pushing for a removal / replacement. He said he will add fluid to it on Monday to see if it will make it shift. He told me that he doubts its just a modulator / bowden cable problem becuase it doesnt shift out of second. I figured if nothing happens when fluid gets added I will take my car back and possibly take it to someone else.

Landseer

Where is it?
Really, only a 928 savvy mechanic needs to touch one of these.

dcrasta

So to be clear :

With the car in D from a standing start it shifts once (first -> Second) and that's it?

If it stays in the first gear I would make sure the Kickdown relay/switch isnt stuck in the energized position. This particular issue has occurred to me and I resolved it by turning the car off, and mashing the pedal to the floor repeatedly. Eventually I sprayed some electrical cleaner into the switch.

Low fluid can cause the condition you described .

JHowell37

+1. Especially if this is a transmission shop. All those places ever want to do is "rebuild" transmissions and hit you for the removal and installation. I'd service the transmission and have it filled with Dexron VI. Then I'd adjust the Bowden cable as per the service manual. This usually means no pre-load and no slack. If it still won't shift, loosen the Bowden cable ONE turn, and one turn only.

1989porsche928

JHowell37 - its a Porsche repair shop, I don't think they rebuild transmissions.I asked him to troubleshooft it (didnt want to get a phone call saying I have to pay $9,000 without notice). I told him Friday if he could fill it up to the correct amount of fluid and see if anything happens then I am going to take it back (then build a troubleshooting model and go from their). I am thinking of buying some stands to evenly get the vehicle in the air but I want to make sure I have all the tools and parts needed first.

decrasta - The car will not shift out of second. I am assuming it would start in first if I smashed down on the pedal (wont do it until transmission is fixed). Before I brought it to the mechanic I pressed down on the switch underneath the drivers pedal with my finger several times to see if it would go up and down and it did go up and down. I also turned the vehicle in the on position (even turned the car on) and pressed down fast to try and hear something. I didnt hear anything click from the inside but it probably would be more accurate to have someone do that while I am underneath the car.

1989porsche928

I found manual titled auyomatische getriebe 722.3 online. It shows very good images of the transmission. Ill post some updates of the progress when i get the vehicle back.

1989porsche928

Dcrasta you mentioned the fsm does not recommend flushing the merecedes manual mentions flushing if fluid smelled burnt. I will take your advice. From my understabding i need to rotate the engine to the 20 degree mark (not sure what size socket i need) so i can see the drain valve on the torque convertor. Then i drain the fluid out of it as well as the transmission through the drain valve.

dcrasta

Flushing IMHO is a shortcut method recommended by those franchise transmisison shops (Cough-- AAMCO). I have several personal friends who have had horror stories of 'transmission flushes' gone bad. Some shops add solvent and other 'additives' to aid the 'flush' process. Some will use 'generic' ATF or improperly fill the transmission. If this shop is an experienced MB/Porsche shop then of course I would say trust them as far as you know them, and suggest you get some references from previous customers if possible. That said.


I am an Amateur Supercar Mechanic. I only work on my car and close friends vehicles. I do not believe in it the 'flush' method, and I think the drain and refil method is a more through way of doing this.

Your issue could be as simple as a sticking kickdown relay or misadjusted bowden cable. If your mechanic is not capable or willing to check the cheap/free things first you should question the motivies .. Just like a doctor trying to put you on perscription meds, I would get a second opinion and attempt to check the simplest things first.

What happens if you throw a 'new' or rebuilt transmission in and it turns out the real problem was a tight bowden cable or tempermental kickdown relay? That mechanic is not going to eat the $$.

Check the simple stuff yourself first . No harm and no $$ wasted. (Besides, its in your best interest to understand how this car is supposed to work if you do not want to get screwed in the wallet..).

Somewhat related :

My girlfriend has a 2005 Honda Passport (truck) . SHe had been getting the 'Check engine' light and the famous TCC code. The dealership, her 'friend' aka mechanic, even a third shop swore up and down 'You need a new transmission'. I told her, that code was an electrical fault code and not a true indicator. We reset the CEL, changed the transmission oil and the filter (Even though three people 'swore' up and down there were not servicable filters on this transmission.). I threw in the Max Life Valvoline, drove great for about 3 weeks. Then we got the CEL light again. After resetting it yet again, I (troubleshooting) was able to determine the convertor would not lock up in 4th gear (highway). So if she put the car in 3 it would drive for days no problem, as soon as you get on the highway and go into 4th OD, CEL. Longish story shorter :Replaced the control solenoid for 3rd and 4th gear lockup .. NO more CEL , no more lack of accelleration and the total cost was < 50 bucks (Junkyard Solenoids). Simple to check a solenoid (especially the grounded on the case/one wire type). Some bench testing and now she wont listen to the Mechanic , or the stealership who tried to get 4k from her pockets.

Sorry for the long winded ness. Coffee makes me type fast and I didnt notice!
YMMV

Bilal928S4

I think you meant "changed the transmission OIL and the filter"

JHowell37

Before changing the fluid and filter, you can put in a bottle of Seafoam Trans Tune. It claims to help break up sludge, deposits, etc. It may work, I don't know. But I usually throw in a bottle of the stuff and drive the vehicle 20-30 miles before I change the trans fluid and filter. So you can run some of that through, maybe it will help, maybe it won't, but give it a shot. Then you can try to change the fluid and filter, and as I said before, refill with Dexron VI.

1989porsche928

Ok got car back today not sure what i posted before but it will not upshift out of first gear. The mechanic says theirs no second or third gear and he added two quarts of fluid.