I spent some good number of years working in a transmission shop doing everything from remove and replace to actual building. I have about a half dozen th350's and about 2-3 th400's under my belt that i have built. if anyone out there perhaps knows more than me to answer a quick question...please do. It seems to me no one runs th350's behind 455's? why not? why always a th400? i know from personal expirience that no transmission in the world is "bullet proof" like some places advertise and it would amaze you how little money it actually costs to build a descent one. it seems in order to do a 455 swap in a 350 skylark i should have to cut and fabricate my driveshaft length, crossmember, and linkage. i know a th350 will bolt to a 455 is there some divine reason why i shouldnt keep my th350? **i have a th350 with full upgrades and shift kit..ect waiting for my 455**
350/400 trans The biggest reason for the heavier 400 is that if your car hooks up well, the front drum will not hold up for very long in a 350 transmission. As you know a steel drum for the 350 is a little pricey for the average person. (not counting the other modifacations you can do to them). I have seen a few people run a 350 transmission behind a 455, but they were low horse and torqe cars that do not get lauched at a track or raced.
Here here I worked in a torque converter shop and it was amazing on how cheap it was. Buy them for 2-3 bucks a pop used. Cut em open [sometime they came off the lathe at 900mph, speawing fluid everywhere 6-8 inches too my left], wash em out, take a hammer and tap on the tabs and make sure all the fins are tight, put in a new washer/bearing [add more for higher stall] weld em back together, pressure check it, balance it and paint it purple and charge $80-150 for them. I cut them open, welded them back together did the pressure check and painted them sometimes. Ohh and the shaft or hub of a TQ as long as the groves are not bad all we did was sand them out with emery cloth. Always sand your TQ hub with some emery cloth so its very smooth. The seals are way over sized and the only thing that hurts them is an un-even surface. Unless it was deep enough too catch your fingernail good we just sanded them smooth on the lathe with emery cloth. -Matt
th350's go boom. My built 350(motor) killed the intermidiate sprag assembly right afther I built the motor up. Replaced the outer race with a heavy duty one, and still broke that... had to dump $300 for a complete front drum/36 element sprag assmebly. So parts wise to build a trans to what I have now, it is about $225 for the rebuild kit w/valve body mods +$300 for the sprag. So you're talking $500+ in just parts to make the Th350 strong enough to handle my 350, and it might not hold up to a built 455. I also had one of the pistons turned down to fit an extra clutch pack in one of the drums, I had the machince shop at my work do it, but someone else probally would have charged a few bucks. Also the normal trans building costs, pressing in bushings, cost me around $50, and any miscelaneous parts needed.... The th350 will have lighter wieght, and less power loss, if you're willing to build it stong enough to hold up...
i have been running the SAME th 350 behind 5 different 455s in my car for 16 years, 76,000 miles and at least 170 driven- to- the- track- and home again 1/4 mile passes-and counting. i drove from southern california to vegas last november for the buick west coast nationals, made a total of 6 time trial passes, 5 eliminations rounds, won the bracket and drove it home again. about 800 miles on the trip as well as the racing. this trans was built CORRECTLY by someone who knows the difference between long term reliability and something that just shifts so hard it spins the tires and beats up the driveline as well as the trans internals. my car has weighed as much as 4200 lbs w/driver to al ite weight of 3500 lbs, currently (vegas weight) oif 3770. i have run a 10 inch 3000 stall converter for 30,000 of those miles and more than half of those passes, although it currently (and at vegas had) an 11 inch 1800 stall converter that is nearly stock. car runs a 9 inch ford rear with a detroit locker and a 3.89 gear for 10 years, switched to a 3.40 last summer just for the vegas trip. car has run as slow as 15.0 @88 mph when i got it to a low et of 12.70 @105-all with the same trans. the only "special" parts in my trans are a hardened input shaft and 2nd drum, with the good hardened sprag race on the back (the part that actually "shatters" on a hard 1-2 shift) these pieces came from an early eighties 4wd chevy th350 pickup, so they WERE available from gm, but nowadays it is easier to buy em from the aftermarket. a th 400 is certainly overall stronger by design-they are also heavier and take more horsepower to turn. in my opinion the th350, with a few good pieces will hold at least 500 horsepower and as proff to that statement, bruce kent, winner of the bowling green nationals in 2000 with his white car, was running a th350 at 10.40s that year.
Wish I had a pic of Joe Chuba's car..anyone know him?He's in Pa. Anyway he has a 69 GS that runs in the 9's w/a T350....... Car leaves wheels up as hard as any,last year at Norwalk he was going high 1.2x 60's.......
I've had good experience with the TH350. My original went in '97- 5 years after I put the 455 in, and it was reverse that went, after 27 years. Supposedly, the tranny I replaced it with was a "built" TH350 (pros did the build and install), but at the time, I would have taken a couple popsickle sticks and a rubber band, if it would make the car move- I had to get to work! After my rebuild 3 years ago, I questioned the TH350, but figured, what the hey, it's paid for. I don't take the car to the track, but I don't exactly putter along, either. I never had a problem. Maybe I will, who knows? Until then, it works. If I get some money, I'd love to put a TH400 in it, even better, a 4 speed manual. But since I'm not exactly rolling in dough, or even have a job...
` I've had 2-3 different 455's in my car over the last 6 years and its always backed with the same built TH350. I'm not running it at great time warp speeds but low 12's and high 11's and the tranny is still with me (Gee, hope I didn't just jinx myself) I haven't changed the tranny since I keep finding more places in the motor to put my money, since the tranny is working fine, why mess with it :grin:
MY th 350 has been in my car for the 11 years I have owned it nothing special just a shift kit and converter it spent 2 years behind the stock 350 and many miles ( was my only car then ) then 5 years behind the 350 running 13.10 in the 1/4 and many more abusive street miles.It has now been behind my 455 for 3 years going 12.30's and 1.68 60 ft's and probably 3000 miles of street use behind the 455. It hasent been apart since it was rebuilt in 92 and if it does go I will never be upset about it and I will probably rebuild it and put it back in and hope for the best.
I've got a turbo 350 that was built for me by a friend in the business for heavy duty usage. I ran it for four years in my 4x4 79 Blazer which besides a few blizzards, I also used it to tow my GS on my open trailer. I wound up dropping a 455 in the truck and I had my trans guy swap the internals into a B-O-P case. I then towed my 24' box trailer for a couple of seasons after totaling the Blazer and tranfering the drivetrain into a 79 4x4 Suburban. I eventually parted out the Suburban and brought the trans back to the shop to get checked out. All that hard usage and the only thing it needed was high-gear clutches. I'm still using that trans in my winter daily driver. It's a crappy 84 Regal V-6 that came with a turbo 200 and I like to refer to as my "sh*tbox". However, it is the only one I know of that sometimes barks the tires on the 1-2 shift! It may not be as heavy duty as the turbo 400 trans in my 87 454 Suburban 2500, but it did the job until I no longer needed it to. I'd have no qualms using that same trans in a GS if I needed to. As a matter of fact you can even buy it off me if you want it, I've already broken it in for you! :laugh: Take it easy.
