Ummm.... the '88 trans is a TH700-R4... your '95 has a 4L60E... The 700 CAN be made to work in your 95-but it's going to take fabrication skill and a lot of experience to set it up correctly, and then your C/E light, or SES light is ALWAYS going to be on because the computer will be looking for the solenoids inside the 4L60E which is what your 95 truck has. They are TWO COMPLETELY different transmissions (though they do share many internal gear train components). They are NOT a direct swap. You should probably be looking to have your existing '95 4L60E rebuilt as finding a good used 95 4l60e trans is going to be darn near impossible. The only way you are going to find a good used 95 4L60E is if someone just had theirs rebuilt, then the truck was wrecked, and you get that unit.. Otherwise ALL 1995 4L60E transmissions are completely worn out by this point in time.. Unless it has REALLY low mileage... How many 95's can you find that have less than 50K miles on them? Right.... If you were close to Houston, I could help you with a rebuild. Keep in mind that 95 is going to be a 1 piece case (non-removable bell-housing), with a LONG shift shaft lever for the neutral safety switch, and a shallow pan. Later units 1996-1998 can be made to work in your 95 by swapping out the 3-2 control solenoid with a 10-15 OHM solenoid... easy peasy... But still... Finding a 1995 through 1998 trans that is not already dead is going to be a challenge. Keep in mind the EARLY 98's were still 1 piece case, but many (most?) were 3 piece case starting in mid to late 1998... You can make a 3 piece case work, but again-more fabrication.. new dipstick and filler tube... trans mount cross member relocation... cooler line rework....eccchhhh..
As a test, go and pull your transmission dipstick.. Hold it up to the light in front of you and look for any rust spots ANYWHERE on the full length of the dipstick... Not just the tip where the fluid is-inspect the entire length of the dipstick, and both sides, for rust.. When you find it, you will have identified the cause of your slipping trans-you need a radiator or to install an external cooler! Every one of these 1995-1999 4L60E's that come through my shop are here because the radiator is compromised, and has filled the trans with engine coolant. If your dipstick has rust-DO NOT just put another trans in as you are going to kill the next trans very quickly! If you have rust, just install a BIG external cooler, and bypass the radiator so that you will protect your new trans from suffering the same fate. It is the safest way. Oh, and if there is water/engine coolant already inside your trans-a rebuild for you is imminent. Water KILLS the clutches, and band, material inside the unit causing delamination. You CANNOT flush water out of a trans, once it is inside...
