43longtime

I am looking to get a th350 race ready transmission and would like some suggestions. I was looking at the tci one summit sells for $1100 but would like to see what others use and would recomend. It is going to be a drag only car.


Thanks

xpndbl3

iTrader: (5)

personally i'd be looking at a th400 with a transbrake if you want to get a drag only transmission. Call a local speed shop and see who builds a quality unit locally. Our "good" trans with a transbrake, ultra bell and good internals could be $1500-2500 depending on power level or billet input shafts, etc

43longtime

why would you go with a th400 over a th350? The only diffrence between the two is the th400 shifts out of 1st for you where the th350 is Manuel. We have a th400 in are other racecar and it shifts out of 1st at like 6400 rpms I am wanting to shift at 7k.
I never thought about calling around and having one rebuilt we have a th350 but someone told us they would charge like 800 to refurbish it. When I could get one from summit for $1100

Thanks
chris

AlkyIROC

It's not just about the gear ratios. When you see how different they are internally, you'll understand why a TH400 is a stronger transmission. Modifying a TH400 to be even stronger is cheaper than trying to build a strong TH350.

I run a powerglide myself with nothing more than a few minor upgrades. I could easily spend $5000 on a bulletproof glide if I had the money.

Race only automatic transmissions rarely use an automatic feature. They'll have manual valve bodies that will hold the gear to any rpm until they're manually shifted.

43longtime

So if I get a th400 will I be able to shift it manualy at the speed I want?
If so what would I have to do to make it do that, Since the one we have in the other car shifts out of first I dont want that.

Thanks.
Chris

AlkyIROC

You normally have to install a manual valve body/transbrake. Some shift kits installed in a full race application may also give you the option. Manual valve bodies remove the governor and shift modulator so the transmission will never shift on it's own.

TH400 manual valve bodies normally also have a reverse shift pattern. That means instead of PRN321, the shift pattern is PRN123. That means once you're in high gear, you can't put it into neutral or reverse without first downshifting through the gears.

The transbrake valve bodies normally also need the transbrake activated to use reverse. The transmission can be in reverse or neutral when the transbrake is activated to back up. In my transmission, I use the reverse light circuit to activate the transbrake to back up. If I put the transmission into neutral, I have to push the transbrake button to back up. If the button is mounted on the steering wheel, it's difficult to back up and turn at the same time so just putting into the reverse position works better.

43longtime

Thanks for that information, I was not planing on running a transbrake on the car. But that is some good infrmation I didnt know about the th400 I will have to look into getting one instead of the th350 then I guess I will need to have the transbrake. So if I go with the th400 I would have to have the reverse pattern shifter in order to not have it shift, is that right.

Thanks

AlkyIROC

A TH400 providing it has a Chev bolt pattern bellhousing, will bolt right up to a Chev engine. There's a lot of TH400's with a B-O-P bellhousing and some have a dual pattern bellhousing.

The converter you planned on using with the TH350 will fit in the TH400.

You'll need a conversion kit for the torque arm and crossmember. The best is to buy an aftermarket torque arm that mounts to a new tranny crossmember designed to work with the TH400.

The TH400 is longer. You'll need a shorter driveshaft. Since this will be drag race only, ditch the factory driveshaft and get a new one custom made. You'll also need a new tranny slip yoke. The TH400 uses a larger diameter output shaft.

As for the valve body, you'll have to look around to see what's available. There may be manual valve bodies available that don't have a transbrake. Installing a transbrake requires some internal modifications so it's not just a simple valve body swap. Forward of reverse shift pattern valve bodies depends on who's valve body it is. Many of the TH400 ones all use the reverse pattern. The shifter itself doesn't care what the valve body does.

For shifter choices, it depends on personal preference. Some people like a gate type shifter similar to how a factory shifter works. I like my Pro Ratchet shifter. The handle stays in the same position from one end of the selection to the other. When the shift light comes on, I slam it forward into the next gear and it ratchets back for the next shift. With a powerglide however, I only have to do one shift.

43longtime

I have my shifter already and I have the b&m pro stick shifter. I will have to look around and see what I can get. If I had to they sell the reverse plate pattern for the shifter I may have to get that.
Will have to see.

90FirebirdTA

So if you put in a manual valve body then it NEVER shifts on it's own? not even if in D or OD ?

fireturd350

iTrader: (8)

Correct. Manual valve body means manual control of shifting. The transmission is not going to automatically shift for you at that point. Depending on the configuration (usually reverse pattern), OD would be 1st, D would 2nd, and so on.

AlkyIROC

Manual valve body, you put it in D at a dead stop and you start off in third gear. That's a little hard on the clutches or bands.

Driving back up the return road or through the pits, I'm usually in high gear. When I slow down to a stop to pick up my timeslip, I ratchet back into low gear before starting off again. You're not going to be able to downshift like a manual transmission. If you're going to fast when you downshift, providing the transmission will even let you, you can easily red line the engine. Going 60 mph and downshifting into low is going to cause damage.

For street use, the novelty of constantly manually shifting an automatic disappears quickly. For drag racing, it's the best way to go.

For street use, the best option is to use some form of a shift kit. The kit should allow you to manually shift through the gears to any rpm but also retains full automatic function if left in D.

90FirebirdTA

Yea a shift kit would probably be the choice in my case. Manual valve body for DD would be pretty pointless.