comicbook8

hi all
i have a 1980 928s euro
gearbox seems harsh when shifting from 2nd-3rd gear up and down normal driving ,perfectly smooth from 1st-2nd up and down
when driving fast box shifts good from 2nd-3rd up and down
any ideas what i should look at first
tks in advance

Avar928

Harshness in shifting is associated with modulating pressure. Check the vacuum modulator on the transmission, if it holds vacuum. Check the vacuum lines from there leading up to the engine. They often break.

Check fluid in the reservoir. Is it the correct level at idle? There's three markings on the reservoir (20, Min, Max), it should be pinpoint at 20 when cold at idle. Has the transmission and torque converter been serviced at all? New fluid for both? New trans filter? New trans pan gasket?

Not sure if this is all the same for Euros but that's what I would have checked on my US '86.

dr bob

And..

It's considered poor taste to use an avatar picture that was created by someone else. Pop a picture of your own car, and use that instead of Checkmates picture please, unless you have his permission.

comicbook8

i did check levels all seem good just seems strange that 1st to 2nd is so smooth but 2nd to 3rd is harsh
not sure when last filter on trans was done for sure . if i change all fluids and filter in transmission torque convertor ,lsd will this help ? its my first auto only have her 6 months every day is a school day !!!!

tks for the advice on avatar i wasn't aware it is in bad taste just thought it was a cool pic as my car is also yellow !i will amend it tks
everytime i try to upload a pic of my car upload fails ...

Avar928

Could be a 2-3 shift flare. You need a K1 spring kit to replace that spring inside the valve body. Very easy once you drop the transmission pan and drain the fluid. Just search it up.

If you're transmission hasn't had it's fluid and filter changed out, it's best to do it now because it's now 34 years old and you want fresh fluid. This will also give you a chance to check the fluid to see what's been going in there (e.g. if it's burnt and or stuff floating inside).

dr bob

Do the standard fluid change and filter, including the torque converter. The refill process is a little involved, since the fluid gets pumped to the transmission rather than poured in. Be sure to get the fluid level correct, measured hot with engine running, trans in neutral or park position. These transmissions are extremely sensitive to fluid level for some reason.

Verify that the vacuum plumbing from the intake to the modulator is intact. I use a MitiVac tool at the intake end of that line to test the line itself and the modulator together as a system before I bother crawling underneath. Under the lower air cleaner housing, the line goes over the middle of the bellhousing and runs along the top of the torque tube tunnel.

After that, any changes you make will be subjective, and limited to adjusting the throttle valve cable for the most part. You probably have some room to tweak the modulator, but be sure to write down any adjustments you make. I usually put witness marks on stuff like this so I can easily go back to where it was originally set if I don't get the response I expect.

The workshop manuals have specs for control pressures, which you are adjusting with the modulator. A better transmission shop will have the gauges for the M-B trans. It's worth a visit, a test drive with their gauges, and an analysis of the results before you go in and start replacing piece$ blindly. Often, DIY'ers go make an adjustment to something that seems to mask a particular symptom, only to find that several other things are affected by that same adjustment. It's way too easy to cause internal damage adjusting things blindly.

dr bob

There are size guidelines on avatar images. Most folks trying to load a hi-res image will crash into that limit quickly. Guidelines on size are displayed when you try to load your picture.

comicbook8

excellent advice on all fronts thank you very much !!!!!!!!