lt4 fd

Hey all, I have an LT1 that I am swapping into either a 1st or 2nd gen rx7 that will be a drag car that I can drive 50 miles to the track and to local get togethers, gutted between 2400lbs and 2750lbs depending on which year car I go with. Now my ultimate goal is to lift the front tires off the ground and with a car that light it may be easier than with a heavier F-body. The stock rear in the best first gen car may not hold up to the power required but Ive heard its good for 550hp and the second gen is not a problem, anyhow it has between a 3.90 and 4.00:1 ratio I forget what exactly. Now the motor most likely will have a heads an cam package at first either an LE2 or LE3 on the stock shortblock and I was curious what tranny would be best to use. It currently has a t56 but I would like to move to a non computor controled auto of either a 200-4r with closer slightly taller ratios or a 700-r4 with a really deep low gear. As for stall speed and torque convertor size I have not the slightest clue, so any suggestions on that would be great I was thinking 4000 or so but again I know nothing in that area.... and again trying to pull air under front tires...

lt4 fd

....hola?

lt4 fd

I thought I would get more responses, would just like to know which tranny would suite me best and what would be a good stall speed about?

rskrause

The optimal stall will depend on the cam and heads. For the best launch (assuming that the car will hook up) you want it to stall a couple of hundred rpm below peak torque. For most street/strip HR cams this means in the 3,500rpm range, but for a big cam it may need a much higher stall.

You will not need a really deep first gear for a car that weighs less than 3,000lbs unless you are going to run huge diameter tire. Unless you plan on a lot of street driving I think you will do not need an OD tranny. I think a TH350 would suit you best. The 1st gear is a 2.52. With a 3.90 rear this would give you a 9.8:1. This is plenty low for a 350ci motor in a <3,000lb car with a good converter.

I am in the market for a T56 along with the pedal assembly and clutch master cylinder. Want to sell yours? Condition not important as I will rebuild it.

Rich

lt4 fd

I am willing to sell and I have the clutch pedal setup but the piece of the tranny that is on the drivers side that bolts into the bellhousing is missing not sure what goes there though.... mine has 73k miles but I guess if its being rebuilt it wont matter, I may hold onto it though havent decided since a few of my friends are real interested but lack funds at the moment, just lemme know what you want for it and Ill let you know...

Anyhow as for the street driving no not around town but every time I go to the track its about 50 miles of highway driving and I dont want to be turning 3500rpm the whole way, how much does a th350 weigh anyhow, I know the 200-4r is about 140 and t56 is about 130...?

rskrause

The weight is in the same ballpark. The OD would be nice for 50 highway miles with a 3.90 rear, but I used to drive around all the time with 4:11's and a 1:1 top gear in my daily driver! If you want OD, the 200-4R's 2.74 is better than the 700. The first gear in the 700 is too steep and the drop to second is too big as a result.

Let me know if you want to sell the tranny, I also need the bellhousing.

Rich

Darrells93TA

i have a Yank Pro Thruster 4200+ in mine. absolutly love it! i get 1.6 60fts on motor with 3.42 gears. with the 700R4.

my car also weighs alot more than youre talking though, 93 t/a with nothing removed for weight.

lt4 fd

Great man thanks for the advice, on the tranny and convertor issue. One question though if the torque curve is flat from say 3500-4500 would you still get the stall around 4k rpm or would you get it right under the big flat spot of torque in the lower 3000'srpm? As far as the tranny goes if you need one right now I may not be the best option since I would like to get that project going before I sell anything just to make sure incase I change my mind I still have a tranny...

rskrause

~3,500 if that's the torque curve.

Rich