Drmark

Hi,
I'm two weeks into my first 928 (1987 S4 auto - UK) and I have noticed slip in the transmission - it only happens when going uphill and is most noticebale when the box changes. It's the same sound / sensation as clutch slip in a manual car. Is this the torque converter? If so does it mean a new / reconditioned one? If so how much is that likely to cost and it a big job labour wise.
Sorry for posting so many questions on my first visit - great site.
Thank you for your help.
Mark

Tony

yes. shame on you for asking a legitimate question of the forum here...geeez!!!

My first stop would be to check the fluid level. The tranny is very senstive to fluid levels. If you can get the car up in the air it is MUCH easier. Since your in England, it will be on the driverside of the trannsmission...a small white container with a red lid. Odds are it is black with dirt. Take a rag and wipe the front of the resivoiur off and you will see some lines imprinted in the plastic for fluid level.

The tranny should be "warmed up" and level when checking.

Hope that helps for starters

jaycm

hey, for some reason these transmissions don't like for the fluid level to be anything but just right. make sure the level is exactly where it is supposed to be. there is a small clear plastic resivoir located on the passenger side of the transmission under the car. it has graduation marks for upper--lower levels. you know, look in front of the right rear wheel. make sure the car is level befor checking. it is a task to add the fluid. i use a large syringe w/ a piece of hose.
if the fluid is brown and nasty looking, now would be a good time for a filter/fluid change.
keep us posted,

Drmark

Thanks Jay and Tony - guess what I'm doing tomorrow?
Hope it does the trick!
Mark

Garth S

Just another comment to reinforce the preceeding advice: Yes to level, but perhaps more importantly, should you not know the service history of the transmission, a full flush of the lines, cooler, and trans is a 'good thing'. If the Dexron is anything but deep cherry red, it should have been changed yesterday. As you know, a fluid service charge is insignifigant compared to the potential cost of Xmission work .
Cheers
BTY, there is also the aspect of adjustment of the control cable - but that is for after fluids ...

UKKid35

I've been told that it's important to have the car accurately level when checking the ATF resevoir, but what do I know, I have a manual.

Did you make it to the 928 meet at the Merry Miller near Oxford today?

Doug Hillary

Hi Mark,
after a cursory check to make sure all cable adjustments are correct and that all electrical/vacuum controllers are intact and working consider the ATF.
There is some evidence that commercially "flushing" the Auto transmission may not be a good practice and I certainly would not do it to any car

Perhaps the best idea in a 928 is to firstly check the condition of the ATF - a "burnt" or "harsh" smell and a darker than normal appearance is a sure giveaway of tired fluid. If it is in this condition fully drain the ATF including the torque converter refilling with a conforming (Dexron 3) and changing the filter - use a OEM filter (or one from the maker, Benz)

If it is fixed then you should drian the fluid again after about 3k - the filter does not need changing again and the torque converter does not need draiining this time

If it does not fix things a deeper analysis is obviously required

All Dexron 3 fluids are not red now. I use Castrol's synthetic "Transmax Z" which is a fill for life (100k) fluid - it is light green. I use it in the power steering too. Blue Dexron 3 ATFs are also being sold

Regards
Doug

Drewster67

It is absolutely essential you use the correct the fluid. No Substitutes allowed.

good Luck

Fogey1

Doug Hilary wrote: "There is some evidence that commercially "flushing" the Auto transmission may not be a good practice and I certainly would not do it to any car."

Anecdotal evidence: I lost a gear in an autobox within a month of a commercial flush. That tranny had 130K-plus miles on it, but had been flawless to that point and had lived all its life with a separate cooler. (HD police package)

I'd never do it again. Drain and fill twice in a week, yes. Flush, no.

WallyP

To check the transmission fluid:
- Car must be level front-to-back and side-to-side.
- The transmission should be fully warmed.
- Engine idling, transmission in neutral (Thanks, Rich!)
- There are three lines on the fluid reservoir - the fluid should be between the top two lines. The fluid should NEVER be below the bottom line nor above the top line with the engine running.

The vacuum modulator is adjustable on your car, and maladjustment can cause the problems that you are having. The modulator is on the left side of the transmission - a round can with a vacuum line attached. There is a removable cap, and underneath is a pull-out handle. Each turn of the handle changes the control pressure by 3-4 psi. You might try tightening the handle by perhaps three turns and see if there is a difference in shift quality.

Tony

This is the modulator Wally is talkign about. You can adjust the "crispness" of the shift with it.

SharkSkin

Fogey's got the right idea. Flushing it out is fine, but only flush it out with recommended ATF. If it's really dirty, go ahead and drain the TC twice. Also crack open the cooling lines to make sure they drain too. (then tighten them back up of course.

Doug Hillary

Hi Dave,
what we both (Fogey1 and I) said is that commercially flushing any Auto transmission can lead to serious problems. There is considrable evidence supporting this

Draining and refilling should not be confused with "flushing"

Probably just confusion over terminology

Regards
Doug

Rich9928p

No one mentioned that the engine should be running and gear selecter on neutral when checking the fluid level! If you look at the level when the engine isn't running you'll think it is overfilled.

Scott M.

So riddle me this...
What is the best way to flush a 928's automatic trans? The picture in the WSM shows some sort of pressure fed line screwed to the tranny line. Will one get enough 'force' using a hand pump style bottle?

Scott