I have a 88 gm k2500 p/u that I junked the 700r4 trans and installed a th400. Does this mess with the computer

Question

There were wires plugged in so I guess it was electronic. I am trans stupid but I do know a 700 should have never been puy in a p/u.

Answer 1

Harry is mostly right. Except the TH400 does not have a "kick-down" cable nor does it have the torq converter clutch. (Bye bye, overdrive!) You also might have to change the front yoke on the drive shaft and the length of the drive shaft.

Answer 2

I have a old Chevy pick-up with a very high horsepower small block, and a 700r4. We built the transmission about 4-5 years ago with race parts, and I have beat the crap out of that thing, and guess what? It's still working just fine! I put a 2500 stall converter with lock-up in it, and have the best of both worlds. We did stuff like heavy duty clutches, a Kevlar band, a heavy duty planet gear, a corvette governor, and a shift kit. It will rattle your teeth when it shifts if you are standing on the gas. The trans came out of a Z-28 camaro. These transmission can be made pretty bullet proof for about $400-$500 in parts. I drag the truck at the strip pretty regular, and street drag a lot, so I can't say a word about them being a bad tranny.
Outside of not having a speedometer, I don't see there would be any problems with it unless you have a check engine light on that won't go away. The gearing on the 400 will kill your gas mileage, and will make it hard to start off, maybe causing the trans to overheat and burn the clutches. First gear will be noticeable higher, and you will be turning up some RPM at 55 mph now. I'm thinking you may wish you had kept the 700. I would have just bought a used one and slapped that baby in it and you wouldn't have to worry about it. Good Luck!

Answer 3

There are no electronic controls on either trans. The wires you see are for the lockup converter (700R4) In some models there is also a plug for an electronic speedometer. (later models) The neutral safety switch is in the shifting mechanism(steering column) this allows it to lock in park when you take the key out. The cable on the 700 is a TV link. It is NOT a kick down cable. It is the only communication between the motor and transmission as they do not have a vacuum modulator valve. This is something you will have to add to get the 400 to shift properly. This should be plumbed into intake vacuum port. It will in no way affect the computer although your RPM's will increase by 25-30% at highway speeds as both trans' have a 1-1 ratio in 3rd gear where the 700 has a 0.69-1 ratio in 4th gear.

Answer 4

The wires should be for the nuetral safety switch. the TH700-R4 and TH400 are both hydraulically controlled, so they should operate fine, as long as you have the TH400 installed properly (TV cable, kickdown, etc). The only other thing I could see possibly messing with the 'puter is whether or not you have the correct speedo gear in place. Other than that, you should be O.K.

Answer 5

I sympathize with you guy! I have done the same thing with mine but its an 84. Those 700R4 trannys are JUNK!!!! Chevy knows they starve for oil which causes them to overheat and burn the clutches out. Nothing you can do either. One guy tells me he drills them out to solve the problem but everyone else does exactly what we did!! I put the 400 in and no problems since. I rebuilt the 700R4 three times in five years. I'm very meticulous about changing from forward to reverse ONLY when I'm stopped.

Answer 6

The converter shaft on the 700r4 can hav 27 or 30 splines also.

Answer 7

The 700r4 has a computer controlled solenoid in the transmission, it could cause problems with your computer.

Answer 8

pie

Answer 9

gj