I've got a healthy 455 in front of a not so healthy th350, and today while scooting into traffic I think second gear let go. Its like instead of hitting second at 50MPH (like always) it just revved like it was in neutral.

I drove it home, and first gear seemed normal, but second didn't seem to be grabbing much at all, barely enough to get me home.

I think third let go last fall, its been slipping like a monster.

A local shop will rebuild my th350 and guarantee it to 600 HP, while I'm running maybe 400HP.

I've been pushing my luck driving without 3rd, I'd have to be really dumb to keep trying to drive this thing, right?

 

I was having this problem a few months ago with my 350, turned out the vacuum hose to the trans was busted and would barely, if ever, shift higher then 1st. All I had to do was put in a new hose, some clamps for added insurance, and all is good. For whatever reason it isn't shifting, even city driving is very tough and even dangerous without being able to shift higher. Not to mention that you have to push the engine so high just to keep it moving. I would get it worked on and be done with it, you will be much happier. That is almost the point that I am at. My shifts are pretty sloppy. It needs at least a rebuild, maybe a shift kit while I'm in there.

 

Usually is not the HP numbers that fry a tranny but the Torgue

 

Yeah I was going to ask that question too...because I have the same setup, a 455 with a 350 trans. I have been itching to upgrade to a 400. Could that be curvewreckers problem too? Or is a stock th350 more then beefy enough to handle the 455? The smaller 350 is good in conjunction with my high *** rearend for cruising on the highway, but I would like to feel the 455's torque pull my skull through my face.

 

A mild 350 will eventually die behind the torque of the 455 if you get on it very much. With slicks you can forget about it lasting too long.
I know when I drive my car it take A LOT of self control not to hammer it all the time. I love the feeling of getting slammed in the seat. I just become a different person when I drive that thing, and that has the potential to get me into A LOT of trouble.

 

I would second that. I guess this one was good for about 3000K.

I have a TH400 on my garage floor.

I am probably going to go the rebuilt TH350 route, because it is always easier to remove and replace a rebuilt unit than to perform a swap. The TH400 is another unknown used trans, and I don't feel like swapping trannys all summer.

Is $600 a fair estimate?

 

The other issues with doing the 350-400 swap are messing with the driveshaft and yoke as well as the parking brake cables (if it still works). The drivesahft needs to be shorter and the 400 yoke is larger. The cables are different lengths because they attach to the crossmember and it gets moved back with the 400.

 

I wasn't aware of the cable issue. I have a custom bent exhaust that might not clear if I move back the crossmember. I don't have the budget for a driveshaft, yoke, etc...

I'm going to call the guy tonight, and see if I can get on his schedule to have the th350 rebuilt.

 

I have had a 455/th350 combo for years now. How many Lb. Ft. of torque are you pushing with yours?

 

My engine builder suggested about 500 pds of torque. Its a +.040 455 with a 1970 OEM cam grind, 1974 heads, HEI, dual exhaust, and soon to have an Edelbrock intake and a newly rebuilt QJ.

My goal is to make this a low 14 second car, and still drive it to work everyday.

Its in a 1977 Cutlass supreme.

 

Well, I have my trans back, and will install it this weekend. Second and third gear were totally gone, and the second gear bands were actually broken. $600 for a professional rebuild sounded good to me.

 

$600 is about right for a quality rebuild. My friend rebuilds trannies and he would have no problem putting a th350 behind a built 455. They are very strong units when built properly and there is less parasitic loss in the drivetrain when compared to a th400.

 

A TH350 will handle a stout 455 easily with a good quality rebuild and shift kit. Premium clutches and band, machine the direct piston for extra clutch plate, dual feed 3rd gear (either with a shift kit or do it internally) and a hardened intermediate sprag will allow a 350 trans to live in a 11 sec car no problem.

 

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THAAAAAAAAAAAAAAAAT would keep it from going anywhere!

 

We installed the rebuild today with 29769 on the clock, now has 29806. So far so good. It is the nicest this 77 supreme has ever driven or ran.

We eliminated the stock radiator trans cooler and went with an external cooler rated for a Class A motor home.

Everything went back into place nicely, reinforcing my decision to rebuild what was in it versus the TH400 I have in my shop.

 

Holy wah does this thing ever drive and ride nice. I think my mileage has gone from 7 to about 13 too! WOOHOO!