1984 300D Turbo Diesel Transmission Slipping?
 

Hello Diesel fans.... I have a 1984 300D Turbo Diesel that has I think a transmission that has been "slipping" lately. Dont know for sure if it's a transmission issue or not. Here are the symptoms: when the car is cold (below 80 deg C) the engine's rpm would shoot up past 3000rpm when I accelerate or go up a sloping road; then the car would go herky-jerky until I ease up on the gas pedal. Now, after the car has warmed up, it drives perfectly fine. The car has 235,000 miles on the clock. Any tips/fixes are appreciated.
Thank you in advance.

You didn't mention if you checked the trans fluid level. Get the transmission up to temp (~20 minutes of driving), park on a level area, leave the engine running in park and check the fluid level. You should be between the 2 marks on the dipstick, preferably as close to the upper mark as possible.

After checking the fluid level, I'd start with the vacuum system. First step would be just checking for disconnected hoses.

There's no vacuum issue that will cause the issues he's describing. Vacuum is used for the modulator which controls shifting firmness, not in-gear behavior.

If you have the correct ATF level.

Drain the ATF and take a look at what is at the bottom of the Transmission Pan. Change the Transmission Filter. Your choice if you want to reuse the old fluid (if it is not discolored or smells burned.) or not. You are basically seeing if it is the Filter or there is evidence of what is going on in the bottom of the pan.

When I accidently disconnected the vacuum to the vacuum modulator it shifted to all gears normally going forward with only a tiny hint of harshness. However, when I let off of the pedal coming to a stop it down shifted extremely harsh. That was a total vacuum disconnect.

I had a 1985 300sd and the transmission would flair from 1st to 2nd. But only if I had it floored.
Well I soon backed off and gave my transmission a break until I could find a fix.
Did some research and found out there was a Mercedes fix for the flaring problem. Cost around $20. BUT you had to remove the valve body and put the kit in which had valves, springs, and it was a long time ago so I can't remember but I put the entire kit in. I also bought the corresponding Mercedes transmission book to make sure everything got put back together and torqued per specification. While at it I replaced the filter and fluid.
That fixed the flaring issue.
If you can't find a Mercedes fix for your problem then I would suggest a transmission shift kit.
I bought a superior K68908AS which is for 722.3/722.4 transmissions. I didn't use the kit because I bought the Mercedes kit. Of course I didn't find out about the Mercedes kit until I already had the superior kit.
Roddy

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Does it do that in all forward gears? Does it do that in reverse?

Pm me if interested in the superior shift kit.
Roddy

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