WILL A TH 350 HOLD UP WELL BEHIND A 383 W/ 2500 STALL AND 3:73 GEARS? A LOCAL TRANS SHOP CAN SELL ME A REBUILT UNIT W/ A SHIFT KIT FOR $650.00. I'M ON A BUDGET AND WILL ONLY BE DRIVING ON WEEKENDS.CAN IT HANDLE 400= HP???THANKS!

First turn off caps lock.

Second more specs on the motor would be helpful. Any idea how much torque? I would think a th400 would be better suited to handle that kind of power but I wonder how well a $650 tranny would hold up to a 400hp 383.

A TH350 can be built to handle 400hp.

A well built 350 could easily handle 400hp, but if it is built as a stock replacement I don't think it will last too long. A $650 trans sounds like a stock replacement and not a performance trans. Do they know what you are going to use it for will they give you a warranty? A friend of mine with a blown smallblock in a '39 Ford, 4.10 gears, really big tires; went thru three 350 trans guaranteed by a local shop. They installed the trans and knew he would abuse it but they guaranteed it. I don't know why? After the third trans I think they beefed it up enough for his use. Took him a little while but he got a performance trans for the price of a stock rebuilt.

Just curious, what was the stock transmission for 454's?

Muncie's or TH400.

Here is the third transmission (THM 350) that was behind my 383

http://elcaminoplace.com/76_elky_files/76_images/broken_thm350.jpg

And this is what was left on my truck.
http://elcaminoplace.com/76_elky_files/76_images/broken_thm350_other.jpg

Needless to say "I don't like em." Notice this in not inside damage its outside. The first was inside damage. Second and third were outside damage and the same transmissions. It broke the bell housing, twisted it in two.

Just what happened to me. :D

Hmmmm.....looks like over enthusiastic driving to me.

my dad's camaro is pushin 500hp with a stock 350 trans. . . it seems to work great, hasn't blown it up yet and he drives hard.

He must drive like an old lady--there is no way a stock TH350 will handle 500hp in a seriously driven car. Sorry pal that is totally bogus.

my dad's Camaro is pushin 500hp with a stock 350 trans. . . it seems to work great, hasn't blown it up yet and he drives hard.

Maybe its the weight difference between the two that is your dad's saving grace. Then again maybe I twisted two 350's in two that were just bad transmissions. I have to admit this is the first I have ever twisted a transmission in to two pieces. Generally the 350s just burn up inside or the center seals go south and then burn up inside.

I am producing around or just over 400 Hp and just over 400 Lb/ft. of torque. And the proof is in the pudding. This is number two for this type of problem for me. The THM 350 is only rated "Stock" to deal with 350 (about) Lb./ft. of torque at best. So maybe your Dad's transmission is not stock or could it possibly be a 400 THM?

I just don't care for the 350 THM transmission I've had too much trouble from them in the past 30 or more years I've been driving and I can say I have probably replaced no less than 15 in different cars and trucks over that time frame. I've had a 4L60e (700R4 electric) in my 93 pickup and with over 188,000 mi on it I have had little to no problems and I pull boats and cars on trailers and it doesn't have an external cooler. So based on that track record I'd say that they are better transmission than the 350s and overdrives at that so there is two pluses in my books.

I hope that you Dad continues to have good performance with his set up its always better to be able to drive it than it is to be able to work on it, especially the transmission.

Hey mrapii, think what you want, but im telling the truth. I have dyno sheets to prove it. If you want, I can send them to you.

This is certainly counter to all my experience. The TH350 is (was?) a good transmission and more of them were built than any other trans in the world but it certainly doesn't belong behind a near 500hp engine.

I just blew a TH350 last night, my second one in less than a month, this one, when pushed hard, sent all the fluid out of the vent tube? I havent a clue to why, someone said it may have been the front pump, they cant handle big power unless heavily modified, Im looking for a th400 as I write this, I need a tranny that will hold realistic HP..



To the guy whom his dad and his 500 hp, take it to the track, dyno's a well, dyno's, and like one dyno oporater told me, I can just about get whatever your after....lol..

2wld4u

From all the stuff I have read and learned about the THM 350, or GM transmissions in general, the 350 is capable of dealing with a Maximum of 350 Lb.-ft. of torque. The 700R4 (4l60) is capable of dealing with 360 Lb.-ft. (Corvette version) and 380 lb-ft. for the version they put in the trucks. The newest incarnation of the L60 is actuallu called 4L65e which is almost identicle internally to the L60 (700R4) but had some improvements and will deal with 400 Lb.-ft. of torque, like the THM 400 and the THM 4L80e.

GM added an extra clutch pack to the 3-4 gear pack and improved and re-calibrated the vlave body, put 6 pinions in the main planetary insted of the 4 that the THM 700R4 has (4L60 & 4L60e) onad one ot two other things I forget exactly what they are. But it seems to me that a smart transmission builder will take those changes and use those in the 700R4s used by car restorers to add that little extra strength. Overall the 700R4 is stronger than the THM 350 in their stock forms.

Gear vendors make a add on overdrive 2 speed unit for the THM 400 that is as strong or stronger than the transmission its self if you want the THM 400 with an overdrive and you do not want to spend the cash to get a THM 4L80e wich is practally the same transmission with an overdrive gear added to it.

first the guy with the pic of the brocken t350 cace ,the problemb could be harmonics from a poorley ballanced tail shaft,and second i have a 68 camaro street car with 640hp 3300pds with a t350 ,runs 10.6 @132mph,and the trans is holding up fine. :-P reg mark 66 elcamino.

The guy with the broken case is not an unusual circumstance. I have seen similar consequences when high horsepower is channeled thru a TH350. I hope that your experience will not encourage other people to use a Th350 with a 600+hp engine....or at least use a explosion blanket around that trans.

first the guy with the pic of the brocken t350 cace ,the problemb could be harmonics from a poorley ballanced tail shaft,and second i have a 68 camaro street car with 640hp 3300pds with a t350 ,runs 10.6 @132mph,and the trans is holding up fine. :-P reg mark 66 elcamino.

Nope not an issue of vibration in the tailshaft. Your weight has a lot to do with the longevity of the THM 350. They are light duity transmissions not intended for engines with lots of torque and heavy vehicles with lots of torque is just not good with a THM 350.

I've went through three THM 350's twice the case has broken and the insides have fryed. Maybe they are fine in a Camaro, to me they are a POS and I will never suggest their use unless you are in the original configuration engine for a 74-86 Camino. That way you only put 145 or so HP to them then they will possibly be ok.

You know Pete that everytime you point out an obvious truth (ie. a TH350 trans cannot reliably handle 600hp) somebody will almost always tell you that they have been doing that for years, it's inevitable. Maybe that one particular TH350 was assembled perfectly and from parts that somehow are infinitely stronger than ordinary TH350 parts. Maybe there is some Black Magic and Voodoo involved or maybe the Gods of Drag Racing decided that a miracle was needed, I just don't know. But I do know that GM never designed that trans for that kind of service and in my many years of drag racing and street rodding I never ran across a miraculous TH350......yet.

Thanks for the help guys- I decided to err on the side of caution and go with the th400-my projected hp is around 400-425.

ok point taken. my t350 has good clutches modified drum and sprag,and a tci valve body. on the other hand my 66 elcaminos . one has a m20 the other has a lenco 4 speed . now we are talking! I drive them all on the street. my girl friend races the camaro because i find autos dull.

I'd say your making the right choice with the 400. Your right at the boderline there with 400-425hp on what a 350THD can handle and survive very long. What's your plans on the tranny crossmember?

You know Pete that everytime you point out an obvious truth (ie. a TH350 trans cannot reliably handle 600hp) somebody will almost always tell you that they have been doing that for years, it's inevitable. Maybe that one particular TH350 was assembled perfectly and from parts that somehow are infinitely stronger than ordinary TH350 parts. Maybe there is some Black Magic and Voodoo involved or maybe the Gods of Drag Racing decided that a miracle was needed, I just don't know. But I do know that GM never designed that trans for that kind of service and in my many years of drag racing and street rodding I never ran across a miraculous TH350......yet.


Well its ok with me. I do what I must to keep my little truck going and it does well enough for me. If someone likes the 350 then thats cool. During the ever so short period of time I had that in and the 3.73:1 gears it always sounded and felt like I needed another gear. Now I have it. :D

I'd like to go back to a stall converter. TCI has one that I like in their Brakaway line. But at this point I don't have the cash to get that so I'll do with what I have.

do I need a new crossmember for my th400? I previosly had the powerglide.