TH350,400, or 700R4/ For BB HP?

[eedgell]

All the auto guys out there. Will all these auto transmisions handle BB torque? I hear " dont use a TH350 with a BB, a TH400 is much better". "Or, dont put a BB in front of a 700R4, it wont take it". What have you all found to be the truth? I am a SM465 kinda guy, but I would like to know the truth about autos.

[keiths69swb]

It all depends on how you drive it.. I had a TH350 behind a pretty stout 396 in high school and never had any problems with it. I currently have a 454 with a TH400, again with no problems. But I know of friends that have had many problems with both. I've never been known to drive things easy but I don't drive stupid either, unlike some of my friends. The 700R4 can easily handle the power, but it needs to be built right. I wouldn't trust a stock one behind a rat motor. Good Luck!!!

[The Big Green]

700r4 would be best imo after you put about a grand maybe more in it.

[WorkinLonghorn]

I agree with Keith above.The 700 R4 can be built up to take major torque.Likewise there are ways to build an "RV" TH 350.For the money and for the long haul I'd go with the TH400.

[The Big Green]

For the record...I've seen them all come apart but that don't stop me from getting any of them...there all good. Its just like our engines there only as good as we build them, if you do it wrong it wont hold up. I built a 350 when I was 16 and it was suppose to be 30 over but when the guy told me he was wrong it was already running, we got it running the same day we picked it up. He was about 8 hours to late. We thought it was loose tourqe convertor bolts...wrong, it was a 30 over looseness...lol...ran like a son of a ***** for 1 year and went to 8 grand by a 16 year old ALOT. It ran great and beat alot of things but when a year pasted it was its time to go and man did it go, 4 broken rods and 3 busted pistons and 1 made its way thru my block. I had 12:1's in that old 355/360 or whatever it was...mixed I guess.

[70cst]

I asked Kurt (who will be restoring my C10 this winter) if I should take out my 400 and install a 700R4 and he said the 400 is more bullet proof than the 700R4 and he wouldn’t think about it. He has built street rods for years and has built up a reputation great body and engine work. There is a reason GM put a 400 behind the BB’s verses the 700R4. I have considered installing a Gear Vendor Overdrive do reduce my rpm's. It still comes down to what you want and as you can see we all have various opinions. Good luck with your choice.

[The Big Green]

He has a very good point, the 400 has almost always been behind the BBC. I have had a 350turbo twice and 400's after that and thats alot of them. With gas prices though the 700r4's overdrive is a good choice.

[DieselEater]

A stock 454 only put out meeger HP anyway...I'd say they're all good to 300 HP no problem. TH400 to 450 HP.....Any more power than that and you'll have to have it re-built to handle it. Go with a mid 90's 5-speed manual (NV4500?). You'll have the strength of the SM465 with the added bonus of an overdrive.

A.....

[cnshoot]

how about a 4l80 i know you think electronics but i have seen that they make a box for these for street rod apps so dont count them out and you could use any of the others listed just depends alot on gear and rpm you plan to run what kind of hp and torque all of this is a variable when chosing what kind of parts and most of all converter choice

[Robznob11]

well i like to go fast and for me its a th350 you can get one for 1200 bucks that will hold 900 ponies and its lighter, shifts faster and has less rpm fall off between shifts than the 400, 700 r4 is good for a street rod but comes with calibration problems not to mention there week and need to be built up also to hold power.but if your looking for that od then you probably are not wanting to go real fast like me...

[ofnaman]

I have ran them all and built them all. I had a stock 350 turbo behind my 11.5:1 355 with a 125 shot of nos. Lasted for 2 years with many 11 second quarters on it. I currently have a 400 turbo behind my 402 in my pickup and I am not to thrilled with it (shifts funny, although its 37 years old and all original). I personally like 700r4's the best (only for the overdrive). I have used the 700 behind many vehicles with very little problems (but they all were built correctly for the application). My friend and I had a 700r4 behind a 327 with a 150 shot of nitrous and never had a bit of trouble with it, even using the nos in overdrive. All depends on what you want, If your building a big nasty big block I would personally look at the 4l80e also.

[Frizzle Fry]

I'm going with something like this behind the 476: http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=B

[67_C-30]

Originally Posted by 70cst

I asked Kurt (who will be restoring my C10 this winter) if I should take out my 400 and install a 700R4 and he said the 400 is more bullet proof than the 700R4 and he wouldn’t think about it. He has built street rods for years and has built up a reputation great body and engine work. There is a reason GM put a 400 behind the BB’s verses the 700R4. I have considered installing a Gear Vendor Overdrive do reduce my rpm's. It still comes down to what you want and as you can see we all have various opinions. Good luck with your choice.

Tell Kurt you can build a 700R4 to be stronger than a stock TH400 for about half of what it will cost you a for $2200 Gear Venders OD. In stock form he's right, but going with the Gear Vendors OD is not cost efficient. The TH400 is power robber as well.

[dastuck]

TH400 would be my first choice if you dont need overdrive. You can also get an aftermarket overdrive if you want to go that route.

[Orange]

I have a 700R4 that will handle up to 750hp, and I love it.
It's a very stout transmission, and I wouldn't balk at putting the power to it.

If you over power ANY of the above, you are going to have problems. Just get one built for your application, and you should be fine. I would stay clear of the TH350 though. I went through 2 of them before I swapped for my 700. Both time it was the intermediate sprag gear that went out, and both times it had been built for a "little more power."

DLB

[utvaquero59]

Sometime in the late 80's (can't remember the year, it's been too long since tech school--but circa 1989) GM revamped their transmission naming scheme. All Turbo-Hydramatics then in production received new nomenclature. The TH-350 became the 3L60, the TH-400 became the 3L80, the 700-R4 became the 4L60, and many transaxles were re-named, such as the 3T60, 4T60, etc. What's all that mumbo-jumbo? The first number is the number of forward gears. The next letter designates how the trans is mounted in relation to the vehicle: "T" transmissions are actually transaxles, perpendicularly mounted in relation to the frame/chassis. "L" transmissions, or conventional rear-drive trans' are mounted laterally or longitudinally, meaning they are mounted parallel with the frame/chassis of the vehicle. Lastly, the last 2 digits represent GM's "thoughness" estimate on a theoretical 0-100 scale or how well a stock transmission should hold up against known torque and horsepower inputs.

The 3L80/TH-400 WAS the torque king (stock trans, keep in mind) until the release of the 4L80-E (E designating that it's electronically controlled thru a PCM or standalone TCM) which shares roughly 70% of its internals with its progenitor, the 3L80. Then, the Allison 1000 debuted in the Duramax and both trannies lost their torque-king status. Incidentally, GM is producing a new, in-house 6-speed called the 6L80-E slated for gas big block duties while the Allison remains in service behind the Duramaxes.

So, while the 3L60/TH-350's and the 4L60/TH-700R4's are only rated at "60," on the theoretical scale as opposed to "80," for the 3L80/TH-400 and 4L80-E, they CAN be built to withstand plenty of torque/horsepower by high quality aftermarket parts.

I personally like the 700R4 for the lower first and second gear ratios for off-the-line grunt and the added OD benefit is also very nice and you can buy a rebuildable core for $200 or so at your local trans shop and, for about $6-800 worth of the "good stuff," you can have as bulllet-proof a 700R4 as you could want. So, you're into it way less than a Gear Vendors (although you'll only have a 4-speed, not a 6-speed like you would should you throw a gear vendors behind a TH-350 or TH-400).

As for the poster who likes to go fast with the TH-350 that's all well and good but OD extends your truck's top speed capability by lowering your RPM's at the same given speed, allowing you to hit a higher top speed before redlining than a TH-350 can do. Just FYI.

[WorkinLonghorn]

Thanks Utvaquero59.That's a really good explanation.Should be included in the FAQ section or something.

[The Big Green]

Originally Posted by Robznob11

700 r4 is good for a street rod but comes with calibration problems not to mention there week and need to be built up also to hold power.but if your looking for that od then you probably are not wanting to go real fast like me...

My buddy has a 65 Chevelle that pulls the front tires and he has the 700r4 TCI that will withstand alot of horseys everday he claims to get around 16mpg in it with that OD. It is built up and if they are there great tranny's. I still think there all great...come on, there Chevy

[The Big Green]

Originally Posted by Orange

I have a 700R4 that will handle up to 750hp, and I love it.
It's a very stout transmission, and I wouldn't balk at putting the power to it.

I just read this and I agree and with gas prices I want one for my 67.

[70cst]

This is very good info on the transmissions but by keeping the 400 it keeps my truck with the transmission that it came with. As far as overdrive I am weighing the options. Again this is very good info.

[The Big Green]

I was talking a few post back about the overdrive being better for gas in keeping the rpm's down. My buddy that has the 65 Chevelle with the 383 and a 700r4 well I just got off the phone with him and in his setup he has the engine and tranny with OD and 3.73 posi and the normal hieght tire because there really hard cars the get a bigger tire under there without tubbing it out. I believe its a 235/60/15 and he runs at 3000rpm at 60 the same as I do with my engine in my Chevy pk. I have a 275/60/15 with a 400th and 4.10 gears. As far as trannys with and w/o OD its to close, I mean the tires make it alittle difference but not that much I would think.

[67_C-30]

Originally Posted by The Big Green

I was talking a few post back about the overdrive being better for gas in keeping the rpm's down. My buddy that has the 65 Chevelle with the 383 and a 700r4 well I just got off the phone with him and in his setup he has the engine and tranny with OD and 3.73 posi and the normal hieght tire because there really hard cars the get a bigger tire under there without tubbing it out. I believe its a 235/60/15 and he runs at 3000rpm at 60 the same as I do with my engine in my Chevy pk. I have a 275/60/15 with a 400th and 4.10 gears. As far as trannys with and w/o OD its to close, I mean the tires make it alittle difference but not that much I would think.

If he is running 3000 at 60 in OD, he has much lower gears than 3.73's. A 235/60/15 tire is 26" tall, and that calculated with a 3.73 gear at 60 MPH with the .70 : 1 OD of the 700R4 he should around 2000 RPM (2025 to be exact).

The same formula proves the RPM your truck is running. A 275/60/15 tire is
28" tall, and that with the 4.10 gear and 1 : 1 ratio will be right at 3000 (2952 to be exact).

If he is not in OD, this would be true. A 3.73 geared car with a 26" tire would equal basically a same final ratio as a 4.10 geared car with 28" tires.

[The Big Green]

Originally Posted by 67_C-30

If he is running 3000 at 60 in OD, he has much lower gears than 3.73's. A 235/60/15 tire is 26" tall, and that calculated with a 3.73 gear at 60 MPH with the .70 : 1 OD of the 700R4 he should around 2000 RPM (2025 to be exact).

The same formula proves the RPM your truck is running. A 275/60/15 tire is
28" tall, and that with the 4.10 gear and 1 : 1 ratio will be right at 3000 (2952 to be exact).

If he is not in OD, this would be true. A 3.73 geared car with a 26" tire would equal basically a same final ratio as a 4.10 geared car with 28" tires.

I didn't understand how he would be at 3 grand either but he does have a 3.73 gear ratio and a 3500/3800 stall speed like I do.

[67_C-30]

Without a lockup convertor, the stall throws all that off!

[Robznob11]

let me further explain the 700 is great if you want over drive...and gas milage
now then lets say you had a 700 hp car and all three trannys rated for 700 to handle the hp... bottom line the th-350 will run a faster quarter every time, the 400 is a known power robber as well as the 700 becuase there gearing is not as good as the th350 not to mention that they out weigh it also and take up more room and even though you could pay 1200 as stated above for a fresh out of the box 350... if you are mechanically inclined you can take a 50 dollar junk yard 350 put about 400 bucks in it in the way of clutches,36 sprag and 700 r4 drum in the 350 so it will hold an extra clutch... and you have a tranny that will hold nos,blower, or big a$$ cubic inches... you take your choice the 4l80 is the best of best with the same gearing and od and able to take the abuse but you have to have a stand alone program to run it. now ill take my little 500 dollar tranny and keep spanking those rich boys who just know how to bold unmached hi dollar parts together