300sdl transmission problem
 

Hello-
My 300sdl is a 300k+ mile car and the transmission is not shifting properly.
I bought the car 50K miles ago at auction so I only know history via
inspection. I suspect the transmission is original. With that backround - the
tranny doesn't shift into 4th gear. Here's what's been done:
- filter and fluid about 10K miles ago, fluid was good then, and still appears
as it should. Also passes the smell test.
- Tried Trans-X 200 miles back - no change.
- Ruled out bowden cable and kickdown switch.
- Checked all vacuum lines for leaks / have not hooked up a vacuum tester.
Now for some additional symtoms. If the car sits for two weeks or so - the tranny will shift into 4th. Although as opposed to the robust / solid shift of the
prior gears- I'll say it sliiiiiides into 4th. The car will shift fine for 20 miles or so,
then I lose 4th gear. If I keep driving - I'll go another 10 miles or so then I'll lose 3rd gear. I havn't pressed my luck past that. I suspect I'm in for a major
rebuild - but would like to have some idea what's causing the problem.
Any help would be greatly appreciated.
Glenn

Well over 300k miles is quite a feat for an automatic transmission that's nearly 20 years old. I'd get ready for a rebuild honestly, but there's a few things you could check out prior to doing so.

The modulator on the case (driver side I recall) could be the problem. You could try pulling those vac lines, cleaning them, and reinstalling too. I believe new modulators are around $35-50. Just a few other things before throwing in the towel.

Hope it helps.

try this: http://www.peachparts.com/shopforum/diesel-discussion/128228-300sdl-engine-trans-vacuum-trans-sticking.html?highlight=300SDL+trans

connecting the vacuum lines back correctly actually fixed my problem. Check that valve on your IP though.

i had the same problem
 

i had 83 300 sd tranny problems and i could not figure it out so i
disconnected the vac to the tranny.... and stuck a stick in it...
at the valv ontop of the fuel pump....


and the problems went away.... so i need a new vac control for the shift...

try this..... :eek: