[Torque454]

I have a 700R4 that i believe is from an astro van which would make it a V6 trans. I was told it worked fine except it had no overdrive. First off, what would cause it to have a problem with just overdrive and nothing else?

Second. What would it take to make a 700r4 capable of handling a stock or almost stock 700R4 in a 79 Chevy truck with a 454 and 4.10 gears? It will need to be CAPABLE of towing 7 or 8 thousand pounds. My work trailer does not weigh that but it might by the time i get done with it. This truck will only be used as a backup truck in case my other truck breaks down. I cannot afford to be down. The truck may be used to haul some light stuff from time to time or be driven around town empty some (this is part of the reason for the 4.10s and the 700r4[overdrive], that and the 3.06 first gear) I could just use a 4L80E but that gets expensive FAST. I think a 700r4 with corvette parts and additional clutches and a large transmission cooler would do the job.

What do you guys think of this and what exactly do I need to have done? Transmissions aren't my specialty...

[F-BIRD'88]

Use a th350 or th400. The OD is useless for towing. You cannot tow in OD. The trans will burnout of you tow in OD. You will not save gas.
You will not save money.

The good old th350 and th400 are much more reliable, especially for towing.

[fast68]

good combo for towing but do not use 4th gear except or maybe on dead level road and constant speed

[Torque454]

I'm not interested in the 700R4 for the overdrive while towing. I want the 4.10s to help tow with, but need the overdrive to get those RPM's down when not towing. That is where the concern is. The 3.06 first gear with the 4.10s would sure be nice too.

The truck has a TH400 (that may need rebuilt) right now but it also has 3.07 gears and a 305 engine. It's all getting changed around, since I need to be able to haul a trailer should my 96 3/4 ton ever break down (like it is right now). A broken down truck costs me money, and not just because i have to buy parts, but because the truck tows my trailer which makes me money. Because of this, i need a backup.

[F-BIRD'88]

Do a search on this forum and any other about the th700r4 and durability even after all the expensive upgrades. You are barking up the wrong tree if you need dependability.

if your truck has a fairly tall tire the rpm with 4.10's and a th400 will not be excessive. The 454 is a mistake. A high torque efficient 350 L31 vortec motor or a LS series motor (5.3L or 5.7L or 6L) is much better. So is the modern OD trans (designed based on a th400) used behind these truck motors. The th700r4 is a looser.

[Crosley]

Keep the t-400 trans and

Buy a Gear Vendors over drive unit. Very tough and durable

22% over with the GV unit

[Torque454]

I will not use another small block. Small blocks and me dont get along. I LOVED my last 454, the only reason I dont still have it is because it got water inside it during the 2 year storage period that it was out of the truck it came from.

As for the gear vendor unit, if i could find one for a good price I would go with that. Otherwise I might as well go for a 4L80E setup, It would be the same price or cheaper.