th700-r4 reverse problem Help please!!!

[magnolia4223]

Hi! I'm new to this, but I have a question that I hope someone can help me with. a year and half ago I bought a 1988 Jimmy 6.2 Deisel. I got the truck cheap, and am now having problems with the tranny. The guy I bought it from towed a huge boat, and has has the tranny rebuilt. Even from when I got the truck it was slow to go into reverse, you had to wait a few seconds and then you would hear a "clunck" and the truck would be in reverse. Now the truck won't go into reverse without using the gas peddle, it still clunks. It will not back up a hill at all. you almost have to be going downhill to get it to work. I was in 4wheel drive when it broke. My husband also did tow a large dodge truck while in overdrive. my other thought was that I had been using the cruise control, could it be the throttle valvle? Any Ideas?

 

[nerfherder78]

Have you looked at the fluid at all? Do you know when it was last serviced? If its low or smells or looks burnt that could be part of the problem (and make sure to check level with engine warm, trans in park). If its just low, then fill it to the proper level and see if the problem goes away. If it is burnt, then changing it now could lead to a bigger problem; new fluid can break old deposits loose and kill the tranny. If that's the case, I'd have a shop or a trusted mechanic look at it.

From what I've heard, towing in OD isn't a really good idea, I think it has to do with the tranny hunting between 3rd and 4th, but unless the previous owner did it a lot, I doubt that did much if any damage, and as long as it shifts smoothly from 1st to 4th, I doubt your TV cable is the culprit either.

 

[drabo]

It sounds like low fluid or a bad pump.

 

[zeitlerusmc]

nerf nailed it Usally when a tranny is low on fluid, a dead give-away is a slow transission into reverse. and it most likely is not the tv cable becasue that affects the shifting(how hard and long between shift points) and yes do not tow in od it will torch the clutches! od is for flat terrain at highway speeds. I would guess its low on fluid. If you fill it and the problem pursists, look into a rebuild or junkyard tranny. 700r4s are getting cheaper! I have rebuilt 6 and it took me 4 times to get it right. If you have the right tools, and good type of media to walk you through it (i.e pics, video) it can be done your self, my best advise is go slow, take pics of the parts as you take them out, and TAKE YOUR TIME!

 

[scogop]

same ol 700r problem

Hi, read your thread and I have a little personal experience with that problem.
I also have 1988 vintage gmc 4x4. t is 5.7 liter though and not 6.2, but it is the same trans. I rebuild my 700r and have had that problem all along and have found out that it is common problem with these 700r, and especially when they get warmed up. One trany guy I know told me it is in the valve body, a reverse servo or something in that order.
But what the other guys have said to do is a good idea.
Make sure you have enough fluid and make sure it is not not burned, or brown or black and not smelly, if it is black well then you have a real bad problem.
But if it is brown you may be able to save it.
Try having the transmission flushed out, and what they should do when they flush it is put it on a machine that will cycle your old fluid out and install new fluid. Have them change your filter before the flush it and also have them put a trans additive in the trans.
Hope that helps
Stevej