ok heres the deal im planning on making some serious hp so i know im gonna have to do something about this tranny. im considering either an LT1Dave stage II rebuild, or switching the trans completely. i know the 400 seems to be a pretty strong trans but its lack of an overdrive turns me off to it b/c the car is my daily driver. however i know that im gonna want to run a transbrake so that pretty much bumps out the 4L60E (never heard of anyone running a transbrake on this trans, and if its possible its gonna take ALOT of money to make it strong enuf). so what am i left with, what about the 700r4 (1993 trans correct?)...how much stronger is it compared to the 4L60E? can i safely run a transbrake with it? what would the cons be in running a built 700r4 vs. a built 4l60E?...price diff.? if this seems like a sensible switch then why arent more people going this route? thanx

 

a 700r4 is a 4l60e without the electric controls. No difference in strength.
The only overdrive tranny that I know of with an available transbrake is a 200r4 and that will be expensive. Or a 400 with a gearvendors OD unit behind it and that will be expensive too.

 

An option I considered before doing swapping in a TH400 for the T56 was a built 4L80E. You can have one built every bit as strong as the TH400. With a full manual valve body you can use a transbrake and have your cake and eat it too - a very strong tranny with an OD. Downsides? Yep, of course. Cost and size and weight. First, I not sure one will fit a 4th gen without major surgery. And it's every bit as heavy as a TH400+GV. Cost will be ~$1K more than a comparable TH400. Why? More parts and supply and demand I suppose.

I decided based on the initial data I could gather to go TH400 with no OD. Because I run 3.42"s I thought I'd give a non-OD tranny a try. After all, I ran around the countryside in the 60's and 70's in cars with 3.73's and 4.11's and thought nothing of it! To date, I haven't put enough miles on it to be sure if I really need the OD or not.

But the 700 R4 really is not an option for the reasons stated. How much power will you be making? Is the 200 R4 an option for you? I don't know of anyone using one, but I don't see why it could be done. OTOH, I wonder about the input shaft, which is 27-spline like the the 700???

Rich Krause

 

so i guess i cant have my cake and eat it too huh ! ill prolly go the built 4L60E route b/c a transbrake isnt that big of a deal, however keeping the overdrive is!

 

or maybe even the TH400...the only reason i wanted to keep the overdrive is b/c its my daily driver and i do alot of high speed highway driving so the overdrive comes in handy . however by the time i get heavy in the mods ill prolly have another car and this will be sort of a weekend car so whether or not it has an overdrive unit wont really matter .

 

Your decision should take HP into consideration. Check it out:

1. A 4L60E can be built to about 700-750HP with the right builder. Disadvantage is no good, reliable t-brake option.

2. A 2004R can be built to handle about 980HP with the right builder. T-brake and OD = best combo if you want that.

3. A TH400 can be built to handle all that a small block can put out and t-brake but no OD and about 5% less efficient. An OD can be added externally but adds weight to an already heavy solution and cost goes up also.

Other trannys should not be considered because they are either too heavy or cost more than other solutions or offer no advantages. The 2004R is the best choice in my opinion. It is efficient, has t-brake option, overdrive, and is well established with the turbo buick guys. The conversion is a bit pricey but well worth it if you plan to exceed 750HP.

 

I tried a "built" 700R4 and tore it up the 3rd time out on the road and decided to give the 4L80E with manual valvebody a try. Really didn't require "major surgery" as described above, but we did have to beat the transmission tunnel in a couple of places so that the cooler line fittings would clear and we did have to fabricate a crossmember. But yes, they are heavy and unfortunately, I haven't really had good luck with this transmission either. The first one I tried, I don't really believe had been "built". I think the people I bought it from just put a manual valvebody in it. It never did work right as shifts were delayed 400 to 500 rpm after shifting--this was a manual valvebody mind you! I fried that one after a short while. The second one I tried was from a different company and it worked great for a while, but then I burned something up in it also. All of this was with street tires. I just sent it back and am waiting to hear from the people as to what they think the problem was. I am willing to try it one more time because the car was really quick with the auto and I want an overdrive, but if this one doesn't work, I'm going back to the 6 speed. I don't take it to the track that much anyway. It sure is fun to nail it and not lift off the throttle when going through the gears, however. Only thing I didn't like (besides it breaking) was that reverse pattern is not available.

Oh yeah, I forgot. Cost--$3200 non-electronic with full manual valvebody and 1200hp rated torque converter. Only requires a vacuum line to the trans for a modulator that regulates line pressure. Since I am running boost, I have to put a check valve in the line that closes as the system changes from vacuum to pressure.

Haven't heard much about the 200R4 but I don't understand if they are such a hit with the turbo buick guys, why don't you see more of them in our cars?

 

David: get rid of the modulator, have it set up as a full race tranny. If it still doesn't work, why not TH400 + GV? After all season getting things sorted out, I am finally happy with my TH400. It needs the OD though, even with 3.42's, to be really enjoyable on the highway.

Rich Krause

 

Thanks, Rich. I had a sneaking suspicion that the problems had something to do with the modulator.

 

It's an expensive conversion compared to the TH400. Most go that route because of cost and give up the overdrive.