roger3

Cracked turbo 350 transmission bell housing last night at drag strip.



On 6th pass I felt a vibration after doing my burnout. Made two more passes.

I have about 150 passes on tranny. 520 flywheel hp, 3:36 gears, with drag radials. I launch at 2000rpm and run about 1.6 60 ft times. Not nearly as extreme as other setups I read about.

Crack goes about 3/4 way around bell housing.

Here's my questions.

What would cause it to crack?

Can cracks be repaired successfully? I'm gonna pull it out and buy another tranny for racing. Would like to repair this one and keep it on the shelf since its original to the car.

Roger

TimAT

Just a guess, but it either was stressed because of too much movement between the engine mounts and trans mount or one or the other. I've seen some cracked but they were in 4x4's used in the mud.

They can be welded (TIG), but with it cracked that far around, you'd need to make sure it's straight.
On the bright side, you're making some decent power and getting it to the ground.

oldalaskaman

you can break a 350 easily with gobs of torque, like flooring it from a dead stop, etc. used to break them all the time in alaska, breaking folks out of the ice. you can weld that , but as cheap as they are better to get another. they make stronger bell housings that you can cut that off and bolt the stronger one on.

Korevette

VHT-Torque-maybe worn mounts = cracks.

When drag racing, all the more call for solid motor and trans mounts to take out any torsional rotation.

Turbo 350's are OK, I have over 650 laps on mine however this might be the time to move up to a "race case" or maybe a T-400.

Super6

Roger,

I didn't remember this went I wrote you earlier today, but I was watching Musclecar(?) the other day and they repaired a cracked bellhousing by cutting it off completely and then using a bellhousing that had a flange on it that used the front pump bolt holes. I don't remember the type of tranny, Ford or Chevy. It was a TCI part, I'm pretty sure.

Fred

Super6

Summit Racing - J. W. Performance: Repair bell housing for TH350, part number JPT-92452 $276.78.

Don't know why I had TCI on the brain.

garygnu

the bolt on bell housing mite be the best fix if you have good hardware in the tranny already.

roger3

Thanks for the info guys.

I am trying to decide if I am going to keep racing the vette or switch to an all out race car.

Roger

oldalaskaman

a cast iron power glide may be a better option if you plan to keep racing the vette

tektrans

I ran mid 9's for years with my old th350 and mine never cracked, Lol and that was with over 700 fwhp. Thats some crack on your trans.
You can weld it. Let me ask you-what kinds of motor and trans mounts do you use?
I keep to one specific on the cars-what I mean is-if I use poly motor mounts I'll use poly trans mount as well. This way the movement in the motor and trans under load has some consistency whereas if they are mismatched one way or the other (rubber/poly) you'll get too much movement on one or the other and stress the bell housing and or the weaker mount.

roger3

Tektrnas,

I have rubber motor mounts and rubber transmission mount. All in good shape and about the same age.

Are the poly mounts stiffer than rubber?

Did you ever try solid mounts.

Your frame had to be a lot stiffer than mine. I don't have a roll cage or any frame braces, stiffeners etc.

Oldalaskaman,

I'm gonna look at power glide.

Thanks

Roger

tektrans

I havent raced this vette yet but yes my old Trans Am had a cage etc.
Poly mounts are much stiffer than rubber mounts. You may be getting too much play with the rubber mounts-maybe that helped to crack your bellhousing. I have torn a rubber trans mount on the old car before.
I myself have never tried solid mounts no.

cv67

used poly/poly and would get a slight vibration on hard accel
Switched to a rubber trans mount solved it. Too rigid a mount will bust one too has to be some give.

roger3

My car was wrecked on left front by previous owner. I believe my frame is slightly bent so it might be more flexible then it should be.

I'm about 90% sure I'm gonna keep it mostly on the street from now on and buy a drag car with roll cage just to race.

I do have a good second gear sprag and a couple other upgrades in my tranny that I want to keep.

Tekttran,

What setup are planning to run ( engine, hp, stall, tires, etc)

Roger

tektrans

My set up is actually pretty close to yours. I'm building mine for 10.0 index.
Pump gas solid roller 406 (530 crank hp)
th400 8" converter
I have a 4 link with a Strange 9" -no gear-only 300 because it's a street car-have no trailor or truck for that matter hehe and need to be able to drive it on the highway.
Motor is built for nitrous but not installed yet. Plan on a 2 stage system DP and plate.
I plan on running MT drag radials.
Just really got her on the road after nearly a 2 year build. She running pretty good-just still working on keeping the trans fluid cool. I need to add another cooler/fan inline because of the 8" converter and I think that will put it where it needs to be.
This pic is with street wheels obviously. Also no more sidepipes they are gone.

gkull

I've been out of drag racing for awhile. So I don't know everything. But I would like to see a link from each one of the people that claimed:



Removable th350 bell housing

iron cased PG

What I do know from my drag racing experience. The motor and tranny can not have any rotation. I ran front and rear motor end plates that clamped onto the frame rails 1.05 60's 6500 stall with trans brake PG

In a non-tube framed car. At the very least I would be using solid motor and tranny mounts.

One of the guys on here from Las Vegas had taken a block save plate and had a shop weld hardened steel wings that bolted to tabs welded to the frame rails. Used with solid motor mounts. total back halved solid rear end car.

7t9l82

i recommend the bolt on bell housing they are much stronger. if you weld it, make sure to drill a small hole at the end of the crack and weld it back. this will keep the crack from starting at that point again

tektrans

Im not aware of any removable th350 bell housing and even the stoutest PG's have an aluminum case as far as I'm aware.
1.05 60's is seriously getting out and in that case yes I agree motor and trans plates is appropiate but even in a 9 sec car and maybe a bit faster in a STREET DRIVEN car I think solid mounts is a bit extreme. JMO-I drove an NA mid 9 sec car on the street for years so I have some experience in lets say...compromise, LOL but the poly mounts are very durable and provide some "give" for street driven vehicles.

7t9l82

the early powerglides circa 1962 were in fact cast iron cases. i am not sure if internally they are the same. a lot of extra weight

gkull

I've never heard of either of these items............. Some people just post anything.



The 1.05's were in my injected alki dragster

i tried Energy Suspension poly motor mounts and they only broke after they were severly melted. I actually had a hard time getting them off because the poly had melted and covered the lower motor bolts. I had to use a torch and burn them away to get a socket on them.

I've run the solid mounts on the motor and tranny for many years