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83 300TD To flush or not to flush tranny?

Submitted by brettbolander on 16 June 2010 - 2:55pm.

I help a friend maintain her 1983 300TDT, and it is due for a transmission fluid & filter change. It has very recently been slipping when in "D" on an incline, such as at a stop sign at the top of a hill. It will just start rolling back. I will be changing the fluid & filter, and plan on using the Lucas additive as well. She has recently taken it to a couple different shops for some work to be done, and someone had apparently overfilled the transmission. I took out the excess with my mity-vac, but the performance remained the same.

My question is this:

What is your opinion of transmission flushes for these older MB auto trannies?

I have heard conflicting opinions about the pros and cons of flushing a transmission with a power flush system. Oh, yeah... the transmission has almost exactly 200,000 miles on it — never having been rebuilt.

I need to know if the power flush is a good idea or not, because obviously if it's a good idea then a shop needs to do the work. I can change the fluid & filter, but couldn't do a power flush.

Thanks in advance for your help!

Brett

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It cant hurt

16 June 2010 - 8:55pm
Kent Bergsma

A power flush can help if the transmission fluid changes have been neglected. It can be helpful if the transmission has a sticking valve body (no shift or jerking shifts). It probably can't hurt a transmission that has been slipping - but don't expect too much from it in this case. If the transmission is slipping in drive under heavy load it usually means the clutch paks are worn out. If that is the case no amount of flushing is going to help. Adding a viscosity enhancer can extend the useful life - but I would recommend you start looking for a replacement.

What models would a donor transmission come from?

28 June 2010 - 1:52pm
brettbolander

Thanks for the info, Kent. A rebuilt transmission may be out of my friends budget at this time. She is thinking she'll have to get rid of her beloved wagon that she's had for 12 years. I was telling her that perhaps getting a used transmission would be an option for the time being, until she could afford a rebuilt at a later time.

Wagons are hard to come by in the salvage yards, so I am wondering what other models/years would work for a donor transmission?

A reminder that this is a 1983 300TDT.

Not sure if there is some difference between the sedan and wagon transmissions. I know the turbo engines have a lot more power, so it stands to reason that the donor car would have to be a turbo version.

Thanks in advance for any help on this!

Brett

Most any 123 turbo will work

29 June 2010 - 6:27pm
Kent Bergsma

First check to see what kind of speedometer you have. It if has a cable (and is not electric) then any 1982 to 1985 123 turbo diesel sedan coupe or wagon transmission with cable speed drive will work.

That's great news!

30 June 2010 - 2:39pm
brettbolander

Thanks, Kent. That's great news, since sedans are much easier to come by in the yards around here.

I assume that hers is a mechanical speedo, since it has a cable that goes right up to the back of the speedo and turns it directly. I don't see anything electrical about it, unless I am somehow missing something.

Thanks,
Brett