I mean i am getting a lot of things built and some things are in motion for me. I talked to Nick from Nick d'agostino(bad speeling on my part) and he is going to build me a complete 370 iron block engine which will be forged with low compression and then i will be getting a front mount turbo charger system and am looking to make approx 750-850rwhp at peak levels. Of course i won't be driving around with that much power on the streets. But i am just wondering what would be a good reliable setup for an auto transmission to work well with those components. Something street friendly driving around town with low boost , and yet somehting to handle the peak power at the track once in a long while.

Overall, i wasn't sure if it would be worth it to rebuild the stock 98 Ls1 tranny or to just buy a whole new tranny in general. I don't mind spending the money on the tranny to get it right the first time and for it to be reliable. I guess i am looking for something that would work good with a 4:10 posi rear.

Just looking for some ideas. Thanks.

 

I can't conceive of a 4L60E ever being able to handle 850rwHP (over 1,000 flywheelHP). I've seen Art Carr try to do it with a 700R4, and he failed miserably. TH400 seems to be the only hope.

 

To be honest, those gears are going to work VERY poorly with your car unless it's fully tubbed with a HUGE slick.

Ben T.

 

Ditto to Fred's post. If you want it streetable you will either need a TH400 with GV OD (like Fred's) or a 4L80E. Both are big $$$ solutions,. But 4.10'as and a non-OD tranny are going to be useless on the street. Actually, it's also too much gear for thrack unless you are using something like a 32" tire (as was also posted).

Rich

 

With that much horsepower he really won't need that steep gear will he? I mean the limited time I spent with the 2.73 setup with my TH400 led me to believe with 300 more horsepower I could live with the highway friendly 2.73 gear or a 3.23 perhaps.
Your not going to get the full potential of the car off the line but I would think 700 HP would still be alot of fun even with the hiway gears in it.

 

I used 3.42's and a TH400 and it still wasn't tolerable on the highway. 2.73's would be a lot better. I suspect it would drive pretty odd in traffic with that tall a gear and a high stall converter? Mine did with the 3.42's, lots of revs without much forward motion. Track would be pretty compromised unless the converter had something like a 5,000rpm stall. He hasn't said exactly what's most important to him. But to really get the best of both worlds, you neeed the TH400+GV OD solution or the 4L80E. For those who like to shift, there are sufficiently beefed up T56's now avaialable.

GM is now making what they call a 4L70E. I know little about these at this time, but I suspect it's a beefed uo 4L60E. This might turn out to be a viable alternative.

Rich

 

Remember, the TH400 only has a 2.482 1st gear (unless you get a custom ratio), so 4.10's may make sense for some TRACK setups. Not friendly for a street car, even with the Gear Vendor. At 70mph with 25.65" street tires, its still pulling 3,100rpm. Without the GV, I was over 3,900rpm at 70mph. With 28" slicks, it will run 132mph in 3rd, with the GV there in case it ever traps faster than that.

 

Sorry to steal threat, but rskrause whats up with the beefed up t56. Who sells them, how much, and does anyone here using one. And whats so beefed up about it.

 

Everything from upgrading the output shaft alone to replacing nearly every major component with upgraded parts is available. Look at these two pages for some ideas.

http://www.gforcetransmissions.com/tran_gt-56.asp

http://t56rebuilds.com/

Rich

 

>what about these guys? :
http://www.mackstrans.com/TremecT56Chevrolet.html

 

I had 3.73s in my stock 10 bolt and it was tons of fun but I was limited to 55 or 60 MPH on the hiway. I broke the pinion and threw in a 2.73 gear rear end I had lying in the backyard. Definately a different feel with a 4000 stall.
Its true it acts more like a powerglide with OD with a 2.73 gear. Really sucked at first but I got used to it, still nothing like the steep gear but after getting used to it I was thinking to myself if I had about 550 600 horse I could live with the 2.73 gear cruise around wherever I wanted and it would still be alot of fun.
Something to think about if its going to be more street runner than track monster.

 

Interesting, I seriously considered this at one point. My car is 3,850lbs though and I just couldn't see that working too well with 2.73's.

Rich

 

My car is closer to 3100 so that would make alot of difference. I have even considered going with a 9 inch rear just to make gear swaps easier.....but switching out a center section just to go to an across town car cruise/show seems a bit excessive.
There has to be a happy medium gear to go with that will let you cruise the hiway with relatively low rpms and still be fun leaving the line.
Compromises........