Sorry if this is too basic but I figured I would get much better answers here than in the newbie forum. I'm looking at an 88 Chevy 2500 pickup, @120k miles with 4WD and an auto, I assume its a 700r4??? The owner says that the tranny keeps going back and forth between 3rd and OD around town but if you put it in 3rd its fine and if you put it in OD on the highway its okay. To me this sounds like the tranny is starting to go and it seems to be common for them to lose 3rd and OD from what I have read. Not knowing newer Chevys too well am I most likely correct or could this be something as simple as a cable adjustment or fluid/filter change? I have been looking at rebuilt trannys and although the truck is only $2000 another $1000 for a new tranny isn't really in the budget right now. I would be using this as my DD and occasional tow rig for my Jeep. Is a TH400 a feasible swap in without expensive adapters, etc... I have heard that you shouldn't use the overdrive while towing anyway on the 700r4s and a TH400 is alot more familiar to me, plus its stronger and cheaper.

it's most likely a 4l80e. same thing as the th400 with overdrive. there tough & towing in od is ok. as for your question, i recomend you visit net.gearhead.com. it's the best exclusive tranny site that i know of & those guys know there $hit.

1st its a 700R4

2dn you never drive in OD in the city. OD is only for the flat higway, not eaven mounten driving. Continuing driving in OD will kill the transmission (ask me how I know)


I douht the transmission is about to go but hunting between 4th and 3rd is normal. Its this constant shifting that kills them


HTH

Thanks for the replies, I am going to check it out tomorrow so I will take it for a ride and see how bad the tranny is. I don't know the owner so hopefully he didn't drive it in OD all the time but who knows??? If it behaves normally in 3rd and OD and doesn't seem to slip between gears maybe it will be okay?

just find out what tranny you have. if it really is a 700r4 then, your screwed. it will need a full rebuild. i have never known of a 3/4 ton with a 1/2 tranny. not even in '88.

From my experiance, hunting between 3rd and 4th is usually from either a lack of power, or improperly adjusted tv cable/vacuum modulator.

Charlo

All of the 6 lug 3/4 tons had 1/2 ton stuff other than a 14SF rear axle. The 8 lug 3/4 tons had the 4l80e.

The 4L80E wasn't even introduced until '92.

It's a 700R4.

I think Charlo is right. Read up on adjusting the TV cable. It's really easy and you could do it when you test drive it. Only takes a couple of minutes to adjust and then you'll know for sure.