Strange A4LD behavior...

[qtrmill]

So a strange problem started occuring the other day and keeps coming up every morning when cold. Back out the driveway and everything works fine, shift to Drive and nothing - no forward movement, no typical jerk into drive... RPM increases slightly like usual but Drive never arrives. If you wait a minute, it slips into drive and works perfectly, all day long, no problem.

This morning the problem occured in Reverse now. Shifted to Park for a minute, back to Reverse and it works. Checked fluid and there is plenty. I'm going to drive it later and warm it up real well and check the fluid again. It doesn't seem like anything is worn because it shifts so well when it decides to give me a gear!?!?

Some background info - it's a '92 XLT 2wd with the original drivetrain with just over 250,000 miles. The trans fluid was changed not too long ago and is still cherry red and doesn't smell nasty. The rear diff fluid has never been changed but I don't think that would affect the transmissions desire to give me a gear or not...?

Any ideas would be a great help.

 

[BrooklynBay]

250K miles on an A4LD is pretty good. You could try to rebuild the valve body first, but expect a full rebuild on the whole transmission some time in the near future.

 

[qtrmill]

Doing some reading and some thinking... the other week when I tried to start up, the engine didn't catch, backfired and blew two of the vacuum lines off the distrubution point under the hood, by the brake booster. Had to put the lines back on to get the engine to start... Think I blew something vacuum related?

What purpose does a vacuum or lack of vacuum have on the A4LD?

 

[BrooklynBay]

Check the vacuum modulator for leaking transmission fluid.

 

[qtrmill]

Just came in from having a tinker around the vac tree... tracing one line back I discovered a modulator/regulator just under the oil filler neck that was disconnected. I plugged it back in and gonna go for a drive - or at least try. Looks like my bush mechanic didn't put the vac lines back where they should lay after dropping the motor to tear out all the freeze plugs... Wish me luck!

 

[qtrmill]

Solved!

Fixed the problem and boy do I feel dumb... So after getting the vac tree all fixed I let the old girl really warm up and upon pulling the dipstick, whaddya know, NOTHING. Took two quarts of Mercon to bring it back to somewhere respectable...

I will say this though... damn are they tough - 250,000 miles on all original major components - I ran it dry of trans fluid, filled it up and still goes like when it was much younger. I just wish the A/C parts were more robust

 

[BrooklynBay]

Thanks for the update!