![]() And when it comes to fun, shifting 3 times is better than shifting two (for me, anyway). The TH400 Short Tail Transmission is also a 4-speed automatic transmission, but it has a different gear ratio than the Long Tail Transmission. so a nice TH350 is a great choice for an auto on your small block (as mentioned). The TH400 Long Tail Transmission is a 4-speed automatic transmission that is used in most trucks and SUVs. But there are several different versions of casings, and on and on. In fact, I actually have much love for powerglides, they are so simple, I used to build them myself. If you can be happy with a hard-shifting TH350, then they are awesome too. But hey, if a 4-speed is ultimately what you want (and I dig that, it's what I wanted), you only live once, don't compromise, - make it happen. Make sure you get a flywheel that is balanced appropriately to your engine type too, btw. Getting the pedals up in there mounting the Z-bar (and getting pushrods through the firewall) carving out the floor (console? rubber boot?) clearing exhaust from the clutch linkage crossmember modifications and the driveshaft will be the difficult parts. But if you want is to have a 4-speed, then line up the prices on everything you need, then decide if you want to do it or not. That is all good too, I'm not bashing it. I have had automatics with shift kits - I've even had them with manual valve bodies. I don't have an answer for your bell housing question, but my 2 cents on the conversion to 4sp: do what you really want, and if you can't afford it right now, maybe sit a bit until you can? I wanted a 4-speed, just for the simple pleasure it brings me. I think you'd be satisfied with a nice firm shifting Th350 and still have dependaility and durability enough to hold up to your mild 327. For a mild 327, the Th350 would be the right choice and Th400 is overkill that does not have as good of a first gear, although minor, more weight, and more parastitic horsepower loss, meaning the Th400 robs more horsepower from the motor to operate it and turn the heavier assembly and gets less horsepower to the rear wheels and to the ground. The ONLY advantage a Th400 has over a Th350 is strength but that comes at a cost. In my opinion, now you're thinking more on the right track. You'll also need to hook up a detent (kickdown) cable for the Th350 to the carb linkage. Vacuum line moves from right front of the trans, to right rear, but this should be easy also. Same flywheel, and you can even use the same torque converter, with exception, you've mentioned your torque converter is ailing, so you'd replace that anyway. Past the driveshaft mods, it is clean easy swap. You will move your crossmember to OEM position, the driveshaft length and yoke will need modified. That's what I did, with the last TH400 he built for me.īottom line, I'm with the other guys who say go with a TH350.I think you mean, change from Th400 (th450) to Th350. 700r4 and Th400- both are products of aluminum. This shifts control to the output shaft speed, and throttle valve. This is different from 700r4 which relies on shift modulation. If I use it, I'll probably have my trans guy swap out the long tail parts, and make a short tail of it. Both transmissions have similar size and construction builds, but the Th400 works with a vacuum modulation. I still have that trans, if anybody would like to buy it. The TH400 is an aluminum cased three speed automatic transmission that was produced by GM. It was "rigged" with a long tail TH400, which worked perfectly. TH400 Transmission Specs, ID, and Common Problems. So, I never used another long tail, til I bought a race ready '74 Ventura, in 2008. The TH400 set-up worked just fine.īy the end of '75, I'd bought several more '68 Birds & discovered the short tail TH400 & correct crossmember & driveshaft for 'em. She won her first 6 races and several others, in '75. It was my wife's(then girlfriend) first drag car. Yeah, it was just a junkyard trans, "rigged" to fit, but it worked perfectly for a few races in '74 & a whole season in '75. ![]() Then, after installing the engine & trans, I took the original driveshaft, along with a TH400 slip yoke, which I'd discovered I needed, to my local welding shop & had it shortened to fit. "If you can't fix it right, just rig it." So, I just made a crossmember with a piece of angle iron. But, back then I said, many times, that you can fix most anything that's made of metal with a torch & welding machine. The long tail mount was so far back, it required a custom mount. I knew so little at the time, I wasn't even aware that there were short & long tail TH400's.ġst thing that was required was a crossmember to hold it up. So, I went to a local junkyard & bought a Pontiac TH400. I'd only had experience with 4-speed Muncie. When I bought my 1st '68 Bird, to make a Stock class drag car, it had a 3-speed stick. I agree that for a 326, it is too much work & expense.īut, it can be done.
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