Should I rebuild my transmission .....

[Zumo]

or look for a 700r4? A rebuild will be around 450.00 It's a TH400. What does it take to put one in our trucks?

[sameyrasmea72]

I vote for the TH400, they are somewhat indestructible. I just had mine rebuilt, it was 35 years old and the guy said it was still in good shape.

[71chevylowrider]

if your not going to be driving the truck much at freeway speeds, then it may not be worth the $$ extra effort to put in a 700R4, oh & maybe this post will help you decide

http://67-72chevytrucks.com/vboard/s...d.php?t=248855

[mnunn454]

I'd opt for upgrade to the 700R4 with it's 30% overdrive and lockup converter only if you're putting lots of miles on the truck and the fuel costs are taking a considerable bite out of your paycheck or fun budget. Upgrading to either a 200-4r or a 700R4 could save you in the neighborhood of 10-15% at the gas pump which will add up over time.

Regarding what's required to upgrade compared to your TH400, you'll need a shortened driveshaft with a new front (tranny output) yoke, a relocated or different tranny cross member, a tranny cooler (a MUST), a little 12V wiring for the lockup converter, and very careful hookup of the Throttle Valve (TV) cable. Don't get a TH700 earlier than about 1989 (maybe it's '88) as the early ones are weaker.

If you're not being pinched by the fuel costs, then I rebuild the TH400. It's arguably the best and strongest tranny out there, fairly easy to find parts for and to upgrade, much more tolerant of trans fluid overtemp conditions than the later model trannies and requires none of the mods listed above.

I have a TH400 in my 454 69 with 373 rear gears. If I keep the truck, I'll upgrade to TH700 just so I can go on out of state cruises and car shows etc w/o it eating me alive on gas. If it stays a "local" weekend fun buggy, I'll keep the TH400 and never look back.


JMO.

[Zumo]

Thanks guys this helps. I was not sure of the benefits of upgrading.

[SCOTI]

I loved driving my old truck everywhere. If you like getting out on the highway, go w/the O.D if your rear gears are 3.73's or lower (higher numerically).

That was my biggest complaint about the 6cyl/3spd combo in my 68 (besides the trannys... 3 of them.... giving up the ghost). When I would get out on the highway to drive to shows/swap-meets, it would rev like nobodies business (3K plus RPM @ 60~65mph) even w/29" tall rear tires. It would wear you out & that just plain sucks.

I'm looking forward to driving it again @ a more freeway-friendly 21~2200rpm.