Massive torque w/ 700R4

[karlcore]

Just wondering if anyone out there has any actual experience running a 700R4 with a BBC that puts out a ton of torque. I'm planning my next project and am planning an engine that puts out 500+ ft.lb. of torque, however I'm a tad scared about tranny options.

[myclone]

Just wondering if anyone out there has any actual experience running a 700R4 with a BBC that puts out a ton of torque. I'm planning my next project and am planning an engine that puts out 500+ ft.lb. of torque, however I'm a tad scared about tranny options.

Sorry but Im not running a BBC but a lowly V6 thats putting out over 500ftlbs. Coupled with all wheel drive, 15psi boosted launches, and a 3400lb vehicle Ive broken about every part of the 700 including the case. With that being said I think I can shed some light on the subject so here goes...

A 700 can be built to take a fare amount of tq but IMO once you pass the 450ftlb mark its life will be shortened directly proportional to how far over 450ftlbs you put through it, how often you do that, and how well you hook that torque up. Constant floggings at the track with sticky tires will break it period....it may be your first WOT throttle run or your one hundreth but it will break. There are ppl out there that have put 700s through the ringer and theyre still holding up but I can promise you they are the exception rather than the norm and they will eventually have to repair the trans at some point. However, if you are running short/stiff side wall street radials then most likely youll blow the tires off before mortally wounding a 700 at least for a while.

I dont know youre budget but if youve got your heart set on using a 700R4 style trans I recommend, at the very least, having it retrofitted with 4L65E parts such as GM 5 gear planets (700/4L60s are 4 gear and none of that ebay off shore junk please) and cryo treating everything you can. Even then its still a crap shoot how long it lives as once you approach the 650ftlb mark the output shafts start to break, the GM 5 gear planets shatter, input shafts break or the splines strip, etc.

Heat.... Heat kills ANY trans but be aware that 700s will start to shred themselves when temps go up. Install the biggest trans cooler you can fit/afford to keep the temps down. You can not over cool an auto trans generally speaking unless you live in the arctic circle (not many tracks there anyways ).

Personally Ive yet to break the last 700 I built (I quit counting after 22 builds/rebuilds BTW) but Ive spent minimal time at the track this year and have yet to make a full WOT pass on the new combo (tuning issues). Do I cringe every time I mat the gas when the lights come down? Good God yes as I know its just a matter of time until this unit scatters its guts all over the track and thats why there is an 80E sitting on the bench waiting to go in since actually racing the vehicle is way more fun than rebuilding the trans after every 1/4 mile pass or so.

With all the above rambling being said and IMO if youre truly going to flog the car any at all with decent tq numbers and ample traction save yourself some grief and step up to the 4L80E. Its expensive up front but once you grenade a couple 700s and have replacements built youre going to be approaching what it would have initially cost you if you would have went with an 80E to begin with. There is only a slight weight penalty for the 80E since its only about 40lbs heavier than a 700 (yes, Ive weighed the units) and performance converters for the 80E are only about 2lbs heavier than a 700 converter (stock 80E converters are STUPID heavy so dont use a stock TC).

Be very VERY cautious of anyone that is selling "bullet proof" or "it'll take anything you can throw at it" 700s. While Im not going to start throwing names around a "bullet proof" 700 does not exist period no matter who builds it. Can one be built to take some abuse for a while? Yes, but usually a few months after any warranty that the trans came with has expired I see the same guys with these "bullet proof" units asking what they should do since the trans is now dead or dying. Get what Im saying?

To sum it up:

Big torque+700R4+street radials and occassional floggings=it'll prolly last a while.
Big torque+700R4+slicks/drag radials=you stand a REALLY good chance of walking home if you flog it and you will eventually.

[6'9"Witha69]

A while is all relative. My SBC 383 has 542 ft/lbs and I have lunched many a 700. I am just waiting for the current one to break (has about 50 miles on it) so I can justify buying a TKO to the wife.

[mini69]

I Built A 700 4-r For A Friend W/ A 91 Z-28 And He Went Through 3 Transmissions Before Mine And He Has W/ Nitrous Shot 900 Hp And He Has Gone Through A Whole Season Of Racing And It Is Still Running Strong. Well See How Long It Last.

[SPEEDZONE]

Just build yourself a stout TH400 and put a Gear Vendors unit behind it. You can put all the power you want to it and it will never break. Plus you have the added benefit of splittling the gears which basically gives you six speeds. If you are concerned about weight, the Gv doesant wiegh much however, put it begind a TH350. You cant go wrong.

[myclone]

Nick is correct that everything Ive stated is all relative... My version of "beating" on a trans may be somone elses version of tame. Then again I show it no mercy and pound the trans with everything the motor will put out when racing which means I can speak with the BTDT experience.

With that being said IMO it boils down to each individuals situation. If youve got the money then by all means step up to an 80E or a 400 with the GV unit and all but forget about the trans. For budget reasons, space constraints or youve got your heart dead set on using a 700 they can live for a while under high torque/abuse (theres that "while" and "relative" thing again) but do not be suprised when it scatters all over the track at some point. As long as youre aware of that then pick whichever trans combo fits your situation.

[blown69nova]

As you can see the general concensus is don't do it unless your going to use some sissy tires that will never hook, but why have 500ft lb's?

[myclone]

As you can see the general concensus is don't do it unless your going to use some sissy tires that will never hook, but why have 500ft lb's?

.

The only reason not to have 500ft/lbs is when you can have 600, 700, or more.

In all seriousness once you really start breaking down how the trans will see that 500ftlbs the life span could be any length of time. Is the car set up with gearing, cam, etc so the trans is pounded with high torque right off the line or is the car a top end/high RPM screamer? Its WAY easier on the trans to deal with 500ftlbs at half track since the vehicles mass is already moving rather than the trans having to deal with it from a standing start. So that means whatever trans is used should be engineered into the entire combonation unless the builder considers it just a way to connect the engine to the diff and nothing more. If thats the case then the builder will be disappointed in either the performance or the lack of durability.