my buddy is getting me to help his buildup. the goal is a a street driven lt1 with 300 shot (DP). i have a good deal on a TH350 lined up. i dont really trust the 4l60e so i was gonna go the th400 or 350 route. i got a killer deal on a 350 right now that i can build up later. with the streetability goal, we will need an overdrive? what is the best way to meet this goal? i know gear venders sells this. what kind of tranny is everyone running with this much power, it wont be sprayed more than a few times a month. it will not be terribly beat on, just a weekend bruiser.

is there any cheaper way to get a good streetable tranny than the TH route with an aftermarket overdrive. i dont know alot about trannies so be kinda with your explanations.

also we want it to be manually shifted just for fun, lol. is this not reccomended?

 

4L80E may be the best solution. I decided to stick with the proven TH400 + GV solution. Actually, the GV won't go on until next year. One thing lead to another and the money just wasn't there to buy a GV on top of everything else.

Rich Krause

 

is the 4l80e the truck tranny? does this hold up better and will it bolt right in with computer changes? how much is a GV setup?

anyone got any more ideas?

 

A good friend, (in the Buffalo area, Rich) just added a GV to his THM 400 in his 560 fwhp '70 Olds which runs about 117 @ 4000+ lbs. with a 4.10 gear. He really likes cruising it now...less than a tank to the 1/4 mile dragstrip!

I, too like the 4L80E idea, but it's costly.

Link to Gear Vendors;

http://www.gearvendors.com/index.html

 

Them built TH400's aint cheap either! Nor was the Coan converter. OTOH, you probably didin't need to spend what I did on a TH400. I bought it from Carl Rossler and he felt that I could get away with his "basic" competition TH400, suitably set up for street.strip use. That would be in the $1,500 range with a brake. I wen with the all out version at about double that price. Probably overkill, but I hate breaking parts.

But as the Old guy said, a 4L80E is even more costly, all else being equal. A 4L80E is a heavy duty OD automatic based on the TH400 which can be built up to be as strong as a TH400. As I said, it is even more costly depending on exactly how it's built. I was tempted to try this solution, but feel that I may find the TH400 without the OD acceptable due to the high 3.42 rear end I run. The $L80E is also pretty bulky and heavy, though not as heavy as the TH400+GV combo.

Rich Krause

 

so what is the cheapest best route for my appliaction? i think the th400 is probably the way to go, maybe? i want that OD and my rear gears are gonna be at least 342, prob 373s. say i already have a th400 in my car, so it has three speeds. how much will it be for a GV overdrive to bolt on (is it just a bolt on)? the GV website is spanish to me. or should i just say screw it and stick with the 4l60e? can it hold up to 700rwhp?

man this is hard, maybe i should just convert to 6 speed, lol.

thanks for the help BTW

 

It's in English on my computer. Well, they are in El Cajon. That may have thrown you off.

Figure "3 large" and you'll be close.

Here's the breakdown:

http://www.gearvendors.com/prices.html

Price code A for a THM 400 application. You'll need a shorter driveshaft and a little massaging of the floorpan with a 2 kg. hammer.

 

so that price is 2200 for a performance built th400 with an electronic overdrive ready to bolt in, minus the DS? that aint bad at all. does this simply hook into my computer?

 

Unfortunately, $2,200 is the price for the OD, no tranny included. And as the Stroker suggested you will also need a new (or shortened) DS. So a good TH400+GV will run in the $4K range and you will still need a converter. And you can spend more on the tranny, though for "just" 700hp that isn't necessary.

The 4L80E is an OD version of the TH400. Price for a beefed up 4L80E will be in the $2,500-3,000 range. Controlling the OD and the transmission may involve another few hundred bucks for an aftermarket controller, unless the ECU you are using can control an electronic tranny. Alternatively, it could be set up as a full manual with switch operated manual OD. A new DS will also be needed.

So, the 4L80E in some form is the least expensive hi-po automatic OD setup. I came close to buying one but preferred to try a TH400 w/o OD first and go from there. I bought a tranny that is a known quantity and I could at least get some $$$ back out of if I find that I want to switch again. Either a TH400 or a 4L80E will need a good external tranny cooler, so figure some additional money on that as well. Speed costs, or everyone would be fast . Assuming you can do the install yourself, I'd budget $4,000-5,000 for a race 4L80E including converter, tranny cooler, DS, plus miscellaneous.

BTW, the 4L60E will not hold up to 700hp on a consistent basis. Figure ~500hp, no more. So what about a manual tranny? I am assuming he is going to drag race this car? If not, a T56 is great and will have no problem with 700hp on street tires. A manual tranny that will hold up to 700hp and racing is another thing altogether. The options are very expensive and not very practical.

Are you SURE you need an OD? With 3.42 gears, 4,000rpm is 90mph with a 26" tall tire. You can run a SBC at 4,000rpm all day. It's noisy and will use a lot of fuel though! Around here, highway speeds are in the 75mph range, just 3,300rpm with a 26" tire. I will see, but I think I can live with that as my car isn't used for long trips.

Rich Krause

 

Keep an eye out for a used GV... I got mine for $1,500. It had been used with an Art Carr TH400 in a 1,000+HP 3,900# 4th Gen, and provided neck-snapping shifts under full load. It was only removed to dump the weight when "street driving" became less important than running low 9's.

It basically replaces the tranny tailshaft housing, and uses the same tranny mount/support point as the TH400. Driveshaft needs to be shortened obviously. Didn't have to do any serious tunnel clearancing. Did have to have the DS loop relocated.

The GV comes with an intricate electronic package that will activate it on the street, keep track of how often it is used, make sure you don't use it below the minmum recommended speed, etc. I just bypassed everything, and wired a couple switches up to the single solenoid that activates the GV.... rocker switch for highway cruising, PB in the shifter handle for the track.

I would only use the GV for a street 'n strip car, the weight is a real penalty for a "track only" car.

 

thanks guys, that was a lot more of what i was looking for. yes this will be a mainly street car with an OK amount of strip time. we like the idea of the t56, but we dont want a heavy clutch and we are scared of missing shifts with that much $$ in the engine. that is why i am scared of the t56, plus the launches are not gonna be a walk in the park to pull a great 60 time on this combo. so it looks like i will have to sacrifice my want for a automatic or alot more money. i dont know what route i will go. maybe since it wont see consistent nitrous shots, the 4l60e can hold up? what do you guys think? the 4l80e seems like a more viable option now than the th400. we want to be able to drive this car 2 hours to the beach and not think twice so i think that OD is much needed. maybe i should reconsider the t56 (dammit)? thanks a ton for the replies, ill keep my eye out for a GV, LOL.

PB

 

Does anyone know how much torque you can push through OD gear in a 4L80? I know that the GV units are rated for something insane in the thousands of HP range... I've got a project on the back burner that I'm hoping to eventually run some 200mph+ runs (landspeed stuff at Maxton), and an OD would sure make it easier.