1996 K1500 5.7 4x4
I bought the truck with 177,000 I went through all the repair reciepts and I can't find any where that the prev owner had the fluid changed regularly. I hear it's a 50/50 chance to change the fluid?
My mechanic says the trans seems to slip a very little bit but I can't tell. I added a quart of Lucas trans slip stop. I have put 3000mile on since I bought it and no issues yet. I use this truck occasionally but would like to tow with it next summer about 5 times. 4000lbs.

What would you do?

 

if the fluid is nice and "bright" you might consider changing it, but if it's "darker" I'd leave it be. something about a fluid change this late in life on those trannys seems to kill them... I've heard many theories, but nothing real definative. If it's not giving you any troubles, I'd say let it be.

:chug:

 

I 2nd that. something weird seems to happen more often than now if you change fluid that old - especially if everything is working ok.
you can add a transmission cooler if it doesnt have one already

 

Ya it seems to be a crap shoot. I'll leav it for now until I have all the funds in place to rebuild it. I do have a trans cooler but it's factory and I hear those are not the best.

 

bigr244: Welcome to the forum.

Is the factory cooler an external one or the one the radiator tank?

One downside to changing tranny fluid in a unit that hasn't been maintained is the new fluid will clean out all the crap built up in the seals and it will start leaky like a stuck pig.

 

If it is slipping do not change the fluid it will be worse. These trans did not last very long 80,000-150,000. At this point it is only a matter of time before it is done. You will be very lucky if you can tow with it even 1 time.

 

The trans cooler is a very small external unit.

I have towed about 2000lbs all winter so far through muddy cornfields in 4wheel drive with no problems.

 

Once it starts slipping its like a time bomb.