transmission frustration, transmission death
 

Thanks to diesel don for the help on my transmission vacuum modulator...

Before I jacked up my car, I figured I would test out my transmission without vacuum, to make sure the modulator was the problem. I figured that if I removed the vacuum line, the shifts should be hard, but the revs ought to not increase when shifting. I removed the line, plugged the three way attachment coming out of the white valve on the IP, and drove. There was no real difference at all. I could still drive with a very light foot and have no real slip, and with moderate or full throttle, there was as bad a flare as ever. Coming to a stop I could feel a strong kickdown out of gear that was not present with the vacuum attached.

So, this is the situation, I am hoping that someone can give me some help and advice on what to do.

-Ever since I got the car, I have never noticed more than 2 shifts.

-I got the fluid changed, this is when the flare started.

-I usually drive very lightly, but when I first had the car, I used to drive it hard form a start sometimes... I could floor it and get the revs to probably around the 4500 rpm mark, as it should (with a lot of mnice smoke). Sometime since, something must have happened, as now the shifts are at 2000 RPM, no matter what. The bowden cable is nearly all the way out (I have unscrewed it two whole turns with no help. There arent many threads left before it will be out.

-With vacuum not attached, the flare still happens (I guess this means its really slippage?)

I guess this means that something is wrong with my transmission? Its funny that when I first had the car, the first shift was always hard. I had the fluid and filter changed at the MB dealer, and the shifts got slowly better. I added a few drops of M1 at one point when it was a bit low, but it wasnt much. I then had the fluid and filter replaced after about 25k (just recently), and then the problems began. I had an independent MB shop do the work, so I would guess that the fluid was right (Id guess a quaker state Dexron III fluid). The techs didnt tell me that they noticed anything weird with the fluid, and there was no reason to think so before. They did overfill it a bit, which I pulled out with a topdsider and re-topped it properly with QS dexron III.

Whats my best bet? I dont think I need to do any vacuum fixing, as it seems to be independent. Does anyone know what a dealer would put into an 83 diesel transmission? I would assume a dexron III fluid... Maybe the fluid is the culprit?

Am I screwed and ought to look into getting the trans rebuilt? FOr now if I drive with a light foot, say 1/4 or less throttle, then its ok for the most part. Still cant hit high RPMs until the last shift, but I can minimize flare by acceleration style. But that doesnt fix or address the problem.

So any help would be appreciated. Sorry this post is so long...

JMH

Do you own a mityvac? I have been diagnosing my shifting problems with mine and it really helps to see what the vacuum is doing at idle and at ful throttle.
If the vacuum bleed valve on the IP is not working corectly then shifts will always flare theoretically.
Sounds like you've run the gamut of tests though so maybe someone else will have some other ideas.

I dont have a mityvac, but the presense of the flare with the vacuum line not attached seems to point to some other problem...

JMH

I don't know if this would help but try changing the fluid again since that is when the problem showed up. It can't hurt at this point, make sure the right amount of the right stuff gets put in.

Easy choice if it were me ...

Change fluid and filter ...

Return adjustments to where they were ...

Bottom line - why would something change simply because of a fluid change unless something was messed up?

Do the easy and cheap things first. New fluid and filter.

Perhaps you should either go back to the dealer, or supply your independent with a quality filter and the transmission fluid you want used. The filters sold on FastLane are good quality, and I'm sure you can get recommendations here for ATF. I can recommend Quaker State 4x4 Synthetic blend Dextron/Mercon-III.

Anytime you have a problem that you can pin down exactly when it started (in your case when the independent changed filter and fluid) the probabilities are that something went wrong at that time.

Good Luck -

Ken300D

I had my brother in laws 82 300D over in my garage last Christmas. He showed me that it was flairing so bad between shifts that it seeemed it would blow the engine.
We studied the information provided here and decided to check the vacuum line by pulling it off and plugging it. No change at all. I fiddled with the bowden cable, bu tcould not reduce the flairing. So next we pulled the cap off the modulator and pulled out the small metal flat blade there and turned it one notch counter clockwise. Saw some definate improvement. Brough the car back in and continued making adjustments one 1/8 turn counter clockwise at a time. Within an hour we had it shifting more or less correctly. It still seems to need some attention on the vacuum system, but not at least he can work through that. Before it was so far away from shifting correctly it seemed that the tranny was shot.
Read Steve Brothertons article if you have not already. He shows just what I have tried to explain here, but don't be afraid of trying this. Just make those turns incrementaly and test drive between each reset.

If you want to seek professional help for this problem take your car to Deltrans over on old Baltimore Pike. The owner is Ed and he actually has the knowledge and experience to FIX automatic transmission problems. He is not a "remove and replace" "transmission" shop.

I've used him threee times in the past for MB automatic transmission problems and he has fixed all three problems WITHOUT suggesting a rebuilt transmission as the first course of action.

Tim