I have a 1989 Chevy 3/4 ton heavy duty truck with a tow package. The truck has the original 3 speed auto tranny but it is getting weak after 203,000 miles. The motor has already been rebuilt and I'm looking at doing the tranny next. The problem is I'd rather have and overdrive tranny rather than the 3 speed, due to living in Los Angeles and freeway driving alot. What is a good tough 4speed auto that can be swapped in and mated to the 350? Is a 700r4 tough enough or should I keep looking???

A well built 700 should do it. Install a bypass cooler thats manual. Use a ball valve that you open to put the cooler in the return stream to the tranny. Use a 92 or so case and innards with a early manual valve body and a manual lock up switch.


Joe

a 700 could be built tough enough... but a 4L80E is probably the toughest light truck auto/OD tranny out there, just not a cheap swap.

Well, your truck has a TH400 in it now & it doesn't get much better than that. My suggestion is to keep it & have it rebuilt. Changing trannies is going to cost more than you'll save in gas. If you want to bring the RPM's down slightly, switch to 255/85R16 tires.

TEX

I'm already running 295 85 r16s- the tallest tire I could fit without a lift. It doesn't do too bad on rpms, just thinking maybe a 4 speed would be nicer.