My 89 convert has a problem with the transmission that wasn't apparent when I bought it. Maybe I just didn't notice since I only drove it on and off the trailer and a couple of blocks to my house. The problem is that when it starts out in the drive position it slips a lot. RPMs climb but the car hardly moves. If I start out in Low it takes off fine, a manual shift to second and it pulls positively in second, shift into drive and the slip begins again. I think the car actually sat for two to three years, since the previous owner was very ill before he passed away. I was lead to believe that it had only sat for maybe a year.

My Father in law had a Cadillac Fleetwood that had sat for a year or so and I was tasked with getting the car ready for sale after he passed away, I remember that the car would barely move when placed in Drive or Reverse. After it warmed up I checked the fluid level than repeatedly shifted it from Drive to Reverse. I did this many many times. I would place it in Drive , I felt the hydraulics engage then put it in Neutral then in Reverse and repeated the process. As it improved I drove it up and down the driveway before venturing around the neighborhood streets. After a while full function returned. That car had the Turbo 400 also.

So I'm thinking maybe a filter and fluid change might help. Or is this wishful thinking? I checked the fluid level and it appeared to be overfilled a bit. I'm wondering if the seller had done that thinking that the level was low and that was causing the problem. Anyone had a similar experience? I did a search but couldn't find a similar post.

 

A push and poke really.

The fluid change and maybe the hassle of a filter, maybe.

The o/ring on the suction tube of the filter is known to split, so the pump sucks air, so an overfill of about 1ltr can sometimes keep it going. Never worked for me.

The fact it works manually until D is selected has me thinking valve body issues.

The TH400 is a tough trans, but stale fluid will kill it.

2nd thought.

When D is selected, maybe the lever on the side of the transmission is NOT actually selecting D, so cable adjustment will be needed.

 

Also known as "morning sickness". Can happen on a lot of slush boxes.


My 79 IHC Scout II used the very tough MOPAR 727 auto box. I t began to do this at a bout 100,000 miles on the clock. A driveway flush and filter change fixed it just fine. The filter was very goopy with a gel like substance. Never did figure that one out


Carl

 

All good points. Question does the fluid smell burned? The filter and fluid change is a must But before you install the new filter inspect the old one and the pan for hard debris and excessive soft particulates. If you find hard parts or a lot of soft stuff and the fluid smells a rebuild is probably in order. Good luck

 

Thanks for the responses. I've bought the filter and I need to rebuild the mount so I might as well change the fluid while I'm under there. If it doesn't help I'll only be out a the cost of the fluid/filter change. I'll post my results.