TH400 trannies

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1981ElCamino

Not-quite-so-new-guy
Feb 28, 2008
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I am currently building a 454 along with a th400. My question is that there are 2 different th400's to choose from. One is just a normal th400, the other is the th400 with HD stamped on top of the case. The HD transmission came out of some old truck. What are the differences in these trannies?
 
the HD probably has more clutches and a different "tuning"--line pressure, shift points, etc.
i'd go with the standard 400 and a rebuild. however, why do you want to use the 400? it has EXTREMELY high gear ratios, designed for trucks. if you're on the drag strip only i'd go with a properly built 350. for the street or mixed street/strip i'd use a properly built 200r4. if you already have a 400 crossmember, the 200r4 should fit in. it depends on if it's for the long or short tailshaft 400. (this is a serious question, not a criticism)
 
I'd like to go with a th350 if I could find one cheap, but the th400 I'm getting for like $50 from a friend. This is car will be at the track often, so 4.56 gears should help with those longer transmission gears.
 
you anywhere near NY? i think my brothers got a spare th350.
 
I live in Indianapolis, IN. I just realized that one of my other friends has a 2004r transmission. If I went with that transmission, all I would need is the TC lockup kit, correct? I think I seen them for like $100.
 
I have a th400 HD in my car with a 455. The transmission was out of a 1969 Grand Prix and as megaladon6 has mentioned they do have more clutch packs in them thus meaning heavy duty and let me tell you...this transmission is tough,,,,i've gone through 3 rear ends and one drive shaft, and numerous amounts of tires,, and it is still running great. I have great top end and good pull off the line, your 454 big block will make up for the supposed higher gears, for i don't know how much higher they are than an overdrive transmission's are. But i know that they aren't as tough!
 
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