well went to the track today first time out with the new gears they were only running 1/8 mile made a pass the motor was breaking up fixed that went out again and the motor ran fine but when i got to the finish soon as i let off the gas the tranny blew up broke to big pieces of the housing off the front on both sides and the casing on the rear of the transmission and also broke the drive shaft in half. i didn't feel any vibration while i was going down the track. my brother told me it might have been the pressure in the trans that it built up so much and when i let off the gas it just exploded. could something have went wrong with the converter its a red neck converter i got off ebay brand new. just thought i would see if you guys had any other ideas. this really bites

 

Wouldn't be the first time I 'ved seen a SBC 350 kill a th400 trans case.
Seems like the SBC is harder on the th400 bell housing case than a BBC is for some reason. Not sure why bit have seen many many th400's split the bellhousing behind seemingly mild/modrate small blocks. I've never seen that happen on a BBC/th400combo.

Next time install a torque strap on the left side of the motor. Have to have the converter inspected to see if it is toast or salvagable. Check the end clearance on the crankshaft too. (thrust bearing clearance). Some times when a trans comes unglued it wrecks the engines thrust main bearing. You can do that in car with a crow bar and dial indicator on the back of the crank hub after you drop the trans out.

Might want to consider going to a th-350 for the SBC with a upgraded 2nd gear sprag. Replace the flex plate reguardless of how good it looks.

Tuff break

 

i was going to install solid motor mounts cause the engine was rocking back and forth pretty good i really hope it didnt mess the motor up that would just suck. i baught the trans at a swap meet 2 years ago for $300 thought that was kind of cheap. it almost sounded like a grenade going off thought it was the motor till i seen red fluid everywere in the car

 

Were you running a soild tranny mount with rubber or poly motor mounts? Was the tranny tight and did it have all the bolts? This is the first thing that comes to mind when I hear about a case coming apart.

 

when i put the tranny in i baught a new rubber mount for it. im pretty sure the bolts were tight atleast they were when i put them in could pinion angle have to do something with it.

 

I have seen this happen alot, make sure your dowel locating pins are not pressen in to far. They help keep the trans from moving.

 

Are you coming out of the box in 2nd or 3rd gear? Coming out in 2nd will destroy the inards of one.

 

well dang i did come out in second both times. when i had the 2.73's i just came out in first. why would coming out in second do that. guess i learned my lesson

 

From what I've been told, the sprag will come a part. I always start in 2nd but I run a real deep gear. Try getting the trans in high gear if using a th350 or 400. I've ran a th350 for 5 years starting in 2nd and going to 3rd as soon as I get the tires broke loose. Never broke one internally. Have busted the bell housing off of a few. The JW bell cures that problem. The same JW will fit either a 350 or 400.

 

$hit happens.. welcome to drag racing..

my first run EVER, i blew up my posi 80ft out.. didnt even make it to the 1/8th.. then a few months later, i blew the motor after three runs..

 

i just really hope it didnt do anything to the motor cause when the tranny blew up the motor shut off to i think theres like one or two bolts on top of the bell housing that are holding the case on the rest on the transmission is just hanging there all sideways.

 

Why do you guys launch in second anyways?

 

Don't think he was launching in 2nd. Coming out of the burn out box, and the tires bite, too much for second sprag.

 

After math... i looked at the coverter when i shake it everything rattles inside..also somthing flew off and put a big dent in my left header collector one of my trans bolts broke off in the motor and another trans bolt hole on the motor broke off and theres about a 2 inch size hole under the gas pedel. its like im starting all over again

 

That's some nice carnage you've got there. Bit scary about the hole below the gas pedal though.

 

SH*T you know how to blow them up good maby something did happen in side of that puppy.

 

well i think i narrowed the problem down but in a bad way. when i took the tranny out i wanted to make sure the motor was ok so i fired the motor up the converter was still on the flywheel. it sounded fine so i started upping the rpms slowly and all of a sudden it did the same exact thing it did at the track and blew the converter right off the flex plate.

 

.................You did what?

 

i dont know if the motor locked up or what it sounded perfectly fine while it was running and it was retared the i left the converter on it but in a way im glad i did beacuse now i know it wasent the trans the did that.

 

I'll let someone else handle this shenanigans. Running a car without a transmission with the TC attached is just too much.

 

Don't think 2nd let go. Looks like you broke the bellhousing off and the tranny got in a big bind. You may have done some damage to the engine now. I'd pull it and at least check out the mains. You can do this with the heads ect on. Your flex plate was toast before you fired up the engine. Had to have been bent with the tranny hanging on it. I've busted the bell off of a few th350s, but nothing like that. JW makes a very strong bellhousing, I've used them for a few years now.

 

Definitely a new one for me

 

I've been coming out of the water in 2nd since 2003; hmmm, still hasn't broken. Of course, had a 34-element sprag put in when it was rebuilt in 2001.

Two things that will break a TH400 like that:
1) Loose or weak/inadequate bell housing bolts (personally, I used all Grade 8, and make sure they're tight every month or so);
2) Suddenly letting off the throttle at the big end. I ease off the throttle after crossing.