83 240D Manual Trans rebuild--I finished it, but something is wierd about 3 rd Gear..

[Carrameow]

I finished rebuilding my 1983 240D Manual Transmission--I had tore it down because I couldnt find a new used unit, and my existing unit could not downshift from 4th to 3rd Gear and often missed 3rd gear. I think I damaged it because for 2 years I used 90W gear oil in it vice ATF
When I opened it I found everything in very clean shape except that the third gear synchro Spring had come looose and had been digested by the transmission.
I rebuilt it carefully with a Beginners Luck. I replaced all the Bearings, Synchros and Synchro springs and most of the snap Rings..
I replaced it in the car last Sunday and with a Huge Gasp, put the car in gear and was pleasnatly surprised to see it worked perfectly and could downshift from Fourt to Third Gear!

The only thing WRONG is that sometimes, in third gear, the transmission will pop out of gear into neutral. Also with the Clutch engaged and at a Full Stop in while in 3rd Gear, I will hear a rattling/whirring noise.

In all honesty I think I rebuilt the transmission very well. By saying that, I mean you can only put it back together correctly, and well (it works), or incorrrectly ( it doesnt work). I got Lucky. So I dont think the problem is the Transmission.

The Linkages have been adjsuted carefully, so the only other place I can look is the pressure plate or throw-out bearing. Can anyone diagnose these Third gear problems?


83 240D Manual Trans rebuild--I finished it, but something is wierd about 3 rd Gear..

[stevebfl]

Originally posted by Carrameow
In all honesty I think I rebuilt the transmission very well. By saying that, I mean you can only put it back together correctly, and well (it works), or incorrrectly ( it doesnt work). I got Lucky. So I dont think the problem is the Transmission.

That is a pretty fair statement, unfortunately you are seeing in black and white. I would conclude from your statement that you did not put it together correctly BECAUSE it doesn't work.

There are numerous shimming conditions that affect your problem and as you put it, if it were right, it would work.

It's my guess that the 3/4 shift hub is too far from fourth, the output shaft has too much endplay, or maybe third gear is too far from the hub. Other causes would be parts problems such as a worn slider sleeve, worn shift fork, worn third gear dog teeth.

[Carrameow]

Yes in the back of my mind I wondered if that was the problem. I think I could have got it shimmed right,if I had bugged enough people and asked enough questions.. but I'm in the middle of a mid -life crisis..I went back to my college football reunion and everyone was wealthy and successful...boy I wish I were 25 again and had the same excitement then when I was working on cars.
Now I am 44 and my resume is full of things like rebuilding engines and recreating damaged houses and going to unusual places but I sure wish I had been a Doctor or something....Hell maybe its because its winter

[Kestas]

Chrysler had a similar problem back in the 80's with the L-body. 3rd gear would pop into neutral while driving, especially over bumps. The fix according to design engineers was to strengthen the detent holding 3rd gear in the shifter and increased the draft angle 2° at the synchroniser teeth to increase the axial hold force under load at the 3rd gear.

I don't think this info will help solve your problem, but I thought this precedence might be interesting. I was not only an owner of an L-body with this problem, but one of the engineers handed me the new and improved parts for the fix, and explained the problem!

[Ridge]

Carrameow,

Did you remove the outer shift levers as you were rebuilding the tranny? If you did you may have reinstalled the particular one slightly out of adjustment. Haynes manual shows the distancew of the lever center hole to the front tranny bellhousing surface.

With luck that's your rpoblem, because it's an easy outside fix.

Good luck, very courageous of you!

Ben