1983 300TD transmission issues
 

Just acquired a 1983 300TD Benz with 297,000 miles. Engine was rebuit by previous owner not too long ago. Looks quite nice on the outside and no rust.
The transmission frequently 'flares' when shifting from 3rd to 4rth. Also shifting to reverse is often slow. Can anyone help me diagnose this problem...step by step. I am new to transmission, but am mechanically inclined and can do most of the work myself. Anyone willing to show me what I need to do?
Regards!

Check the fluid. Read the many DIY on transmission trouble shooting.

Welcome to the forum.

Sure, we'll help you with it.

The slow shift to reverse can be caused by an old filter in the trans.........or, it's just getting to the end of it's serviceable life. At 297K, it's definitely past its prime.

The 3-4 flare is quite common.........although it's usually the 2-3 that gives folks the most trouble. To fix it properly will require you to have a Mityvac. It can be used to adjust and check the vacuum system to the transmission. We'll check the vacuum and reduce it slightly to cure the flare.

Post back when you have the Mityvac available for use.

this is a good thread for me to follow! most of my D's are slightly flaring when driving with slight throttle.

I cannot believe that you haven't fixed that issue yet...........:rolleyes:

why? I can pull and tear and rebuild engines all day long, trace electrical and a/c problems till the cows come home, but when it comes to auto trannys, I just have somebody do it for me... and I am waaaaaaay too busy to take the cars in lately. so I gotta learn sometime.

Got your Mityvac ready?

yup, just waiting on your sage advice!

OK, first things first.

Unplug the supply vacuum to the T on the top of the VCV. Connect the Mityvac to this hose and pump up the Mityvac. It will rise to a certain reading and not go above that reading. Report back with the reading.

Observe the Mityvac and see how long it takes to bleed down. If it takes less than 15 seconds, then also do the following:

Disconnect the line that goes to the transmission from the same T. Connect the Mityvac to this line and pump it up again. Now it will go all the way to 20". See if it holds.

Report back.

Mityvac it is...
 

Thanks guys..keep going. I will go and get a Mityvac...
Regards!

While you wait for the Mityvac, you could unplug the vacuum line going from the VCV to the transmission modulator, plug up the fitting where it was plugged in and take it for a test drive. If your shifts get real firm with no flaring, you'll know the problem is in the vacuum system.

Go on......

GOt Mityvac results
 

Disconnected the T as instructed by Brian. Pumped up the mityvac and it goes down to 15 inches Hg and stays there. Then gradually bleeds down to zero over a looong time...more than 5 minutes.

But heres the realy clincher...the T on top of the VCV is connected to absolutely nothing....I cannot find any lines going to the T. Can anyone share a picture of a proper vac line setup for a 300TD (circa 1983) with this forum please?

Thanks!

OK, 15" and holding is fine.

Now, on the top of the VCV is a T. One end of the T goes to the transmission. The opposite end of the T goes to the vacuum pump. The bull of the T goes to the top of the VCV (with green damper attached).

What I want you to do is to remove the vacuum supply line at the T and connect up your Mityvac (other two legs of the T are properly connected as detailed above).

Pump up the Mityvac and get a reading with the throttle fully closed. Report back with result.

With Mityvac fully pumped up, gradually open the throttle and observe the gauge. It should slowly move toward zero as the throttle is fully opened.

Report back with results.

No Joy this Xmas
 

Happy Xmas everyone.
Brian: One issue with following your instructions. I thorooughly checked out the T. The two top ends of the T on my car and completely open! Thats right...when I popped the hood and examined the T, only the base was attached to th VCV and the green damper. The other two sides were...guess what...attached to nothing!!!. I think the previous owner may have done some screwing about there. I need to get some vacuum lines and make the proper connections.
Can you show me where the line from the T attches to the transmission and where it attaches to the Vacuum pump? Perhaps a photograph or a diagram? PLease help!?

Thanks!