Honest opinion: Is it possible to build a 700R4 to be anywhere near as strong as a built TH350?

I'm assessing my options, and I'm leaning toward the TH350 for reasons of cost v. reliability.

Thanks!

 

Until probuilt answers I will share my experience with you.
I have an s-10 with a 700R4 and a 355 that runs in the high 12's, the trans is a stock rebuild with a few mods, no aftermarket parts, no vette servo. It doesn't slip and it shifts strong. The truck weighs 2900 pounds so that helps the transmission.

I have used a 700R4 in a '75 nova with a 400 small block, it had a transgo kit but it didn't seem to like the 2-3 shift, I could feel it loosing time between the shifts, but that was the first trans I ever built and I was unaware of the problems with the 3-4 clutch. It now has a th350 in it, built with all the regular modifications, it runs good too but I miss the overdrive.

In my opinion it's very easy and cheap to built a th350 to handle good power and be reliable. For a 700R4 to handle good power and be reliable it takes some experience and money but it can be done.

 

Hay Mojo, Do what I did. Go with a built th400/Gear Vendors combo. So what about the money. If you wanted to save money you wouldn't have a Vette. Just dive right in and do it. I think you have already looked my web site over and found the page about the tranny conversion. I am very far from having any mechanical skills and I did it all myself. And I designed/engineered/ and constructed my own torque arm. I'm very happy with this setup. It works great. For autocrosses it is very cool to be able to split each gear to give me just a bit more gear before that next set of cones. Trust me, you will be glad you made the right decision if you do this. There. Now all you guys with 700r4's that havn't broken yet can chime in and say how great they are. Just my opinion on this one guys, no need to jump all over me and such.

 

Bob,

I thought about it, but the overdrive isn't worth the gear vendors price to me. If I'm going to swap, it'll be to a TH350. I can use the tail from my 700R4 and build an adaptor for the torque arm very easily. Currently, it looks like I may not have to worry about it at all. Someone is pretty seriously looking at buying the car as it sits. I just don't have time to deal with it anymore. It's been sitting with a broken tranny for a year now, and I still haven't found the time to work on it. It seems that no matter how much money you dump in to a 700R4, it'll never be nearly as strong as a TH350. As you know, this is the 5th 700R4 I've destroyed, and unless I hear a darn convincing argument, I've had it with them.

 

Looks like I wasted my time posting that reply.

If you're going to sell it why not slap something in it and let the buyer worry about it.
I would think if you destroyed five of them and are getting rid of the car .... well maybe that makes too much sense...

 

I think its luck. blowing 5 700R4s sounds like bad luck. Ive got 2, both stock, neither has any problems. "good luck". Ones behind a stock 305 running 15.5's, and the other was behind my 380 horsepower 355 before I put the blower on it. Since its stock, a 550 horsepower 355 with a blower would tear apart my dinky 700R4, however, Pro-built is going to build me a nice new 700R4 that will hold my blower engine... And I put my faith in Sir Dana... Everyone I talk to says hes the greatest, the tranny even comes with a year warranty! who would put a year warranty on a racing tranny? Not me! no way! Yes Ive got a TH350 in my car right now, with a 2400 stall 12" (yes 12 it was free what can I say) and it runs... decent. I dont like the tranny shifts, even with the shiftkit, and it shifts too late because the modulator is crappy and it wont downshift quick enough for me so when I hit the gas it takes too long to downshift, and my detent cable isnt hooked up so dont say check it and blah blah blah... the 700R4 uses no modulator and has a nice cable setup to determine all the goodies... I will never go back to the TH350 unless I suddenly decide to get bad gas mileage again. Im getting 18 MPH with TH350 now, I make 450 RWTQ at under 2000 RPMS and I think my converters about to explode.

 

In the past, I have built a couple of TH350's running mid 10's and doing ok, (no call for them now) but over the last several years I have built a few 700R4's that are in the high 10's and some in the low to mid 11's. The 700R4 will hold up to about 625-650 horsepower max. and live for awhile with the right torque converter. The TH350 with the right parts can hold about 750 horsepower max. As long as there are improvements being developed for the 700R4/4L60E, the horsepower limitation can be increased. The 2004R with the right HD parts can hold 750 HP+ and live for awhile. It depends on what you want to spend and what you are trying to do.

 

I think if you're only looking at reliability/ cost, the TH350 wins hands down. You can through a bucket o' dirt in one of these things and it'll still work. It seems so anyways. Rebuilds are dirt cheap too. I like the Th700r4's overdrive, but for cost/ reliability,
bang for your $buck$,,,no question.

 

How much can a built TH400 handle then hehe I've just pulled mine back out after 2 weeks of driving it looks like some broken bits of metal got into it and toasted the tranny or that's the remains of something in there lol. Nothing like the smell of burnt tranny fluid, the look of metal bits and black sludge at the bottom of the pan Yeah, mine's behind a 305 for now but I'm hunting for a 454 BBC at the moment to blow it up even better next time

 

The potential sale actually came up after this thread. One of my email accounts wasn't working properly, and I had a week old message from a friend with a friend who is interested in the car. Up until that point I've been agonizing over where to find the time to pull the transmission.

Pro Built,

This last tranny actually lasted about 25k miles before the 3/4 clutches started slipping. It started slipping very suddenly as I was passing a line of cars on the freeway at WOT. As far as what I'm looking for, I'm looking for something that will handle around 500HP/475FP reliably for a very long time. I want to spend as little as possible. I could care less about gas mileage, as I rarely drive the car at all. When I do drive it, I want to be able to flog it and not worry about blowing another transmission. Realistically, though, I mostly drive the car like that grandmother who only takes it out on Sunday to church...

 

Probably the intermediate roller clutch, the weakest part of 1971 and newer th400's. I have broken two with a 400hp 357ci. I now replace the roller clutch and direct drum with either 1970 and earlier parts or a 4L80 drum with a 32 element sprag type clutch. A transmission mechanic I know says even a stock 350 can break the roller clutches.

 

i jsut got my 700r4 rebuilt. i had the guy tune it for mild performance and i just love it. now i only got a 357ci and only around 275rwhp, but the OD has me sold...ohh and the life time warrenty, and the free yearly fluid changes. cost me a pretty penny.....1650 for everything including a converter. but you get what you pay for!!

 

Shoot, I would have *gladly* paid that for tranny, converter, and lifetime warranty! I can't get anyone to warranty their work behind my motor for 5 minutes, much less lifetime! You got a deal!

 

yeah i even told the guy that i will be racing with it, and he siad as long as i dont do neutral drops, or get into a accident, hell cover it! well the only hint is that i have to bring it in every year for a fluid change.

 

Mojo, I'm curious as to what goes wrong with the five 700's you have broken. I'm in the process of building a full manual th400 for my car but I may just sell it and build a 700 with the money.
How much horsepower are you putting out? I think I have around 380 to 420 in my current setup. (a '75 nova with a357/th350)

I don't hate 700's yet.

 

I'm not sure of the year on mine but I believe it's an earlier model. Driveline shop said it was an early style slip yoke due to the size it had to be turned down to. When the guy rebuilt it, he did put a 32 element sprag in. From the first time I drove it, first gear would feel like it was dragging it's feet and the engine wouldn't gain rpm's fast like in 2nd. Well, showed my mechanic buddy last week and held it in 1st gear full throttle and the rpms got up to and stayed at 4,000. Next thing was a nice big cloud of smoke and a burnt smell It's at the tranny shop again hopefully getting fixed soon.

 

I'm putting out close to 500 crankshaft HP with almost as much torque. I've done lots of things to 700r4's. I've torn out an input shaft, broken a case... lots of things that made the tranny shop just shake his head. This time it just seems to be the 3/4 clutches. The funny thing is, I went through the first four when I was making a little less power.