Hi everyone, I have a TH400 trans that my Dad gave me. The story is, it was rebuilt in 1985 with all new internals and a shift kit. Problem is it has been sitting since then and was never used. the pump is all full of rust and it won't move (not sure if you should be able to turn it by hand or not) the shafts have rust on them. My question is, if I open it up and give it a cleaning and replace all the seals do you think I should risk putting it in? (if everything turns again) it still has the plastic caps in the holes on the side where the coolant lines go in from after the rebuild. I know that for my car a TH400 is probably way overkill but I already have it. The car is an 87 camaro 2.8/ 5spd and I have a 350 (carb) that is going in there and dont care to swap in a t56. I don't have a ton of money and I'm not building a crazy race car. Car will not be a daily driver and will be used for sunday night cruising and a trip to the track now and then. dont care about overdrive either.

oh and this trans was built for my uncles 1970 chevelle with a 396 but never made it in. any help would be great.

Thank you

 

I would not put a th400 in. All they do is rob power and the low gear sucks. Go with a th350 or a 700r4. As far as the trans you have, I would not put it in. It has been sitting for over 25 years with no fluid in it and will need to be gone through before even considering using it.

 

Ok, thats what I was thinking also but thought id get a second opinion. I also have a TH350 that is in good working order from my 79 silverado that I just pulled out last weekend (thats where my 350 engine came from aswell) I was told that they were super weak so I hadn't really considered it. it is the one with the longer tailshaft housing. Guess I'll use that and see what happens.

Any idea what kind of power the TH350 will handle safely?

 

I know guys running well built th350's behind built big blocks.

 

A properly built TH350 is damn near as bulletproof as the TH400. Also, as stated above, the gear ratios in the TH400 aren't as good. A lot of racers say the TH350 has the perfect ratio spacing between each gear. If you put 3.73 gears in the rear, and run about a 3200 stall converter with a good shift kit in that TH350, your car would be quite the animal! One of my buddies has a 90 Iroc, and he managed to blow up 2 or 3 700r4's in it, then he turned around and put a TH350 in it. It totally blew my mind when he called me and said he blew up the TH350 within a couple of weeks! I was like, holy cow, how in the heck did you kill one of those that quick! Of course he finally admitted that he was fond of doing neutral drops (revving the **** out of it in neutral, then slamming it into gear). That kind of stupidity would kill any trans you put in a car! I had a 77 Camaro with the stock TH350 in it. I never even changed the fluid or filter. I put a small block 400 in it and beat the snot out of that car, and the trans never had a single problem.

 

Thanks for the reply, I plan on a mild build with Vortec heads, a lumpy cam, Air gap intake and a 750 carb. with a 3200 stall converter this car will still be ok on the street? sorry I dont know much about transmissions. I am also unsure of what to expect for HP numbers with a set up like I am building. should be a nice street/strip toy I hope.

Thanks,

 

What is wrong with the 700R4 you have now?

A mild build with vortec heads will make about as much power as a stock 2011 v6 Camaro. I wouldn't be too worried.

-- Joe

 

700R4? refer to first post or signature, Car is a 2.8L/5spd.

Thanks for the reply though

 

oh and a stock V6 camaro, isn't that about 300hp? I wanted a little more then that, maybe I should rethink my plan. I was hoping for closer to the 400 mark.

thanks for the insight

 

Sorry, I missed the 5spd part.

Still, just put a 700R4 in it if you want an auto.

400hp on L31 heads ? You are going to have to really work on the heads, compression will need to be spot on, etc.

-- Joe

 

the reason I'm gonna use the th350 is because i already own it, I would like to see the 400 HP level but maybe I just need to reconsider the route that im gonna get there. Guess I must be living in dream land expecting those kind of numbers.

 

What is the length of the TH350? It needs to be 31". If not you need a longer driveshaft. Either way you will need to get an adaptor or re-work the cross member, the mount is almost two inches away from the stock location.

-- Joe

 

not sure of the length, I'll have to measure it. it has the longer tailshaft housing on it, came from my old 79' silverado. as for the crossmember, I wonder if the one out of my 1980 camaro would bolt up? or I'll just have to cut and weld the one from the 5spd or buy a new one.

 

No, the 2nd gen crossmember won't work. You just need to weld a tab or something to relocate the mount if it's in the wrong spot.

Not sure on the silverado 700R4. Did 2wd have the same spline count and shaft diameter as the cars?

-- Joe

 

the tranny from the silverado is a th350 and it has 27 splines just like the one that was in my 2nd gen camaro only this one has a longer shaft housing. I also have a automatic overdrive tranny from an 84 cutlass supreme i could use..... not sure what it is though. it says 422G or something like that on the bellhousing. choices choices. might be better off with the OD though. hmmmm.......

 

The cutless might be a 200R, which is fairly popular with the 1st and 2nd gen guys because it's the same size as a TH350.

It sounds like your TH350 might work out. just measure it. You need 31".

My only complain about a Th350 is the lack of overdrive.

-- Joe

 

X

 

The Gear ratios are as follows: TH400 2.48 - 1.48 - 1.00 TH350 2.52 - 1.52 - 1.00
So these is no difference here. As far as the TH400 eating more horsepower (when in stock form), is only true when you have extremely low rear end gears 4.88 - 5.13 etc. In some comparison test, I have seen the TH400 actually quicker than a TH350 in somes cases. The reason is that the low/reverse setup in the TH350 is it uses 5 clutches, and the TH400 uses a band. Once the band is off, it does not rob any horsepower as the rpm goes up. With the TH350 the 5 clutches take more horsepower to spin as the rpm goes up. One way to help here is to use the turbulator steels in the low/reverse clutch pack in the TH350 from a 1996 & up 4L60E. These take less horsepower to spin. And it takes very little for the TH400 to handle 750 - 900FWHP.

 

From what I've seen with most street machines, it's kinda interesting when you see the difference in the proper stall speeds for the 700r4 and the TH350. For instance, if you put a 3000-3200 stall in a TH350, if you have a 700r4, 2400-2600 stall speed will act the same as the 3000-3200 in the TH350. I've never really understood how the 700r4's work great with the lower stall speeds in comparison to the TH350 with the higher stall speed, but that's the way they are. For instance, my brother has a 69 Camaro with a 350 engine, TH350 trans, and the Comp Cams 280 Magnum camshaft, and he's running a 3200 stall B&M Holeshot converter. Then there's my 89 Camaro, which has a 350 motor and 700r4, and my cam is very similar in size to my brother's, yet my converter is only a 2600 stall. If I put a 3200 converter in mine, it'd be way to much stall speed. Anyways, bottom line is, if you're going to run the TH350 trans with the engine setup you mentioned above, going with either a 3000 or 3200 converter would probably be ideal.

 

I was actually thinking that I would use the stock converter for now as I know that everything from that set up is in good shape. I dont really need anything crazy for street car. I think even if I end up at around the 300hp mark it will be ok until I can build a proper engine for the hp level I want. should still be a fun street machine.

 

Does anyone know how I can get the th350 to bolt up to the stock T5 trans cross member? what needs to be modified? is there a thread explaining this? or some pictures somewhere?