how to build a strong th350

[purplemonte]

Anyone have any good sites or suggestions on how to build a strong th350?

[kwkracing]

You dont, u get a th400! lol

[DirkaDirka]

You dont, u get a th400! lol

From just reading what everybody has been saying about the TH350's I am with kwkracing. From what I can tell the TH350 wont hold up to the horsepower like a TH400 can. IMO

[MEMRACING62]

the weak spot in the th350 is the sprag assembly if you build or have it build make sure you go with the best aftermarket one you can buy. money well spent!

[cepx111]

the weak spot in the th350 is the sprag assembly if you build or have it build make sure you go with the best aftermarket one you can buy. money well spent!
X10,000

My buddy has gone thru more than a couple of them buggers on his th350, he got the best of everything in that department and it still tears up.
I'd get a th400 or better yet, a powerglide.

[TopspeedLowet]

The trick is to start with a turbo 400 case, then assemble it with the parts that fit in the case. This is the most durable 3 speed trans that GM makes.
A 350 is best left to the hot rod / car show / show car wana bees
However, for thousands of dollars, there are several trans shops that will make a 350 as strong as a stock $200 dollar 400.
Bruce

[johnracer]

the weak spot in the th350 is the sprag assembly if you build or have it build make sure you go with the best aftermarket one you can buy. money well spent!
I ran one years ago in my low 11 second bracket Nova and the intermmediate sprag is the weak link. High gear only burnouts made it last much longer. I usually carried a spare direct drum/sprag asm just in case. Finally went with a glide 15 years ago and am still running it in my 8 sec Vette roadster........
Johnny

[purplemonte]

ive been running the one in my Monte for 11 years now with a 4000 stall running 7.70 in the 1/8th and for the last year with a 100 shot of nitrous and its still together and its basically all stock inside . I like the tranny , its light and I like the gearing. Its time for a rebuild and if it held up at the dragstrip for this long im sure if I upgrade to some better parts Ill still get use out of it for a long time. Thanks for the recomendation on the sprag.

[shawnp]

Purple...sometimes things unexplainable just happen. You have had some incredible luck with what you have. I would be almost afraid to touch that thing. You know how it works with performance parts, just when it is supposed to make something better......well, I think we all have been there and done that.

[kwkracing]

ive been running the one in my Monte for 11 years now with a 4000 stall running 7.70 in the 1/8th and for the last year with a 100 shot of nitrous and its still together and its basically all stock inside . I like the tranny , its light and I like the gearing. Its time for a rebuild and if it held up at the dragstrip for this long im sure if I upgrade to some better parts Ill still get use out of it for a long time. Thanks for the recomendation on the sprag.

Maybe your tranny is slipping too, a 7.70?

[purplemonte]

Maybe your tranny is slipping too, a 7.70?[/quote]

The 7.70 is on motor,, Im sure if i took the time to do some tuning i could get it down a couple tenths but for bracket racing ive never bothered. On nitrous it averages 6.9 to 7.0 in the 1/8th mile with a 1.50 60 ft time. Im sure the tranny is slipping some it was a cheapo rebuild in 1995.

[kwkracing]

Haha, i see i thought with the 100 shot it was a 7.70. And i also didnt notice that it was th350 you where wanting to rebuilt that has seemed to hold up fine in your application. If nothing has broke, just check for excessive wear and if all is fine, replace the seals and clutchs and go!

[chevyfireball]

Sometimes stuff just breaks. I had my glide rebuilt 60 runs back. It had the biggest input shaft available put in. Its a $5000 trans. Well I figured it was due for a freshen up. Just got the word that the input shaft is twisted; the planetaries are stuffed; and the output shaft is twisted; the keys are destroyed. Who woulda guessed at so much carnage. My builder said he can't believe it hasn't flown apart yet.

That trans has the best of everything in there but s*%t still happened.

[kwkracing]

Man i just had to build one of them junk pile 350's tonight for a neighbor.

[JEFF69Z28]

MY 350 HAS BEEN RACED HARD FOR THE LAST 3 YEARS IN A LOW 10 SECOND SS MONTE CARLO(1/4 MILE)BUT WHEN I HAD IT BUILT MY BUILDER PUT IN SOME AFTER MARKET CLUTCHES,HARDEN DRUM AND SOMEOTHER PARTS I CANT REMEMBER WHAT THEY WERE.HE ONLY CHARGED ME 950.00

[ARUSSELL]

I have a Pro Trans 350, all billet internals, spragless hub, kevlar clutches, reybestos bands, not sure who makes the transbreak valve body, but running in is a 565 Dynoed at 1150 hp and 3400lb car. NEVER missed a lick

[cepx111]

I have a Pro Trans 350, all billet internals, spragless hub, kevlar clutches, reybestos bands, not sure who makes the transbreak valve body, but running in is a 565 Dynoed at 1150 hp and 3400lb car. NEVER missed a lick

One thought comes mind, why?

[JEFF69Z28]

Why not,they are lighter,and i was told they build rpm faster than a 400.if it works it works no reason to switch.

[BEAST477]

I have a Pro Trans 350, all billet internals, spragless hub, kevlar clutches, reybestos bands, not sure who makes the transbreak valve body, but running in is a 565 Dynoed at 1150 hp and 3400lb car. NEVER missed a lick

Wow that sounds like a pretty friendly dyno to me.

[TopspeedLowet]

I have a Pro Trans 350, all billet internals, spragless hub, kevlar clutches, reybestos bands, not sure who makes the transbreak valve body, but running in is a 565 Dynoed at 1150 hp and 3400lb car. NEVER missed a lick

Wow that sounds like a pretty friendly dyno to me.

I thought that was obvious Beast477 when the 350 was holding up. They sell these engines based on the builders dyno that gives these generous numbers to sell them. That power figure is probably what he was told when he paid for it.
Then again this engine my have dual carbs with a small NO2 plate Beast?
Bruce

[BEAST477]

I have a Pro Trans 350, all billet internals, spragless hub, kevlar clutches, reybestos bands, not sure who makes the transbreak valve body, but running in is a 565 Dynoed at 1150 hp and 3400lb car. NEVER missed a lick

Wow that sounds like a pretty friendly dyno to me.

I thought that was obvious Beast477 when the 350 was holding up. They sell these engines based on the builders dyno that gives these generous numbers to sell them. That power figure is probably what he was told when he paid for it.
Then again this engine my have dual carbs with a small NO2 plate Beast?
Bruce

Yeah Bruce he could have a plate I guess he didn't say one way or the other. Just going by what a buddy of mine has a 565 w/tunnel ram and a really good set of heads and on an honest dyno (this guy doesn't sell engines) made 902 HP and it runs strong.

[TopspeedLowet]

I have ran the 556" combo myself with similar results that your friend had Beast477. As a comparison of power, my 582"tall deck,12 degree Profiler headed, cast ported profiler intake with near 15 1/2 to 1 comp using a 6 cc dished piston ( due to the small comb chamber) and Jesel 1.75 ratio rockers and .922" lift at the valve with Pac #1349 springs with 1064# on the nose and 375# on the seat requiring 7/16" push rods. I run a single 1400cfm Dominator on gasoline that makes 1170 uncorrected HP at 7450 RPM and 924 # torque from 5600 RPM to 7100+ rpm. Steve Schmidt & company ported the heads and gave me the valve train combo ( I would have never arrived at this answer on my own or budget) a few years ago. We run real fast with our TH 400 trans with a 2.10 first gear ratio. The stock 400 2.41 ratio is too much ratio at this power level on the starting line to hook it up easily.
Bruce

[signsbyesa]

i upgraded to a 400 and sent it to hughes transmissions and they
installed a race kit w/transbrake for $1,250., the guy told me it
would handle up to 1000hspwr, i'll be lucky to push out 800,
but they cleaned it painted it and it arrived looking brand new :wink:

[Tod74]

You dont, u get a th400! lol

rofl

[cepx111]

Why not,they are lighter,and i was told they build rpm faster than a 400.if it works it works no reason to switch.

But, not Lighter than a glide.

The only people who run T400's instead of T350's have never ran a glide before, well maybe a few but not many.

[russ67chevelle]

set it and forget it!!! ill take a 400 in all my stuff!!!

[Scooterz]

Well.... I have a confession to make.

I have a TH350 behind my BBC (hey, it came w/the car). Fact is, it has served me well so far. I have been concerned with constant abuse however. I like that it is lighter & easier to spin, but I do believe I need TH400 & I am exceeding the HP for my application by 50HP according to my trans guy. I figure I will see how she does, then go 400 after that. I wonder if I will need to modify/change my x-member & drive line for the TH400???

[cepx111]

I wonder if I will need to modify/change my x-member & drive line for the TH400???

You can use the 350/powerglide cross member but you'll have to notch it and then box it up to clear the longer pan.

The output shaft is bigger too so you'll need to swap yokes out on the drive shaft.
Goodluck, Cp

[johnracer]

A 400 is longer overall so you have to get the driveshaft shortened and a 400 slip yoke. Also, you'll need to move the crossmember back to mount it up. Personally, I'd go with a glide.
Johnny

[Scooterz]

Thanks John & CP.

For pure bracket racing, I agree.... the PG is best. I just love to be busy & shift a little more... as it is a street car more than a drag car.

I have notched the X-member already for a larger pan... so it may work already. The driveline change, yoke, & new x-member placement sounds like all I need according to what you guys said. I just had the driveline re-done too!! I swear these things are bottomless pits!!! Should have switched the 350 then.... oh well.

[kwkracing]

Having more gears than you need in a street application is harder on the street than a drag application. Because cruising at low speeds running threw the gears, the convertor will constantly slip. I love my glide on the street and at the track, i can cruise the car around in traffic in low and when i hit the highway, bam, high gear.

[Scooterz]

I hear ya, never ran a PG myself; I love a hard smack/chirp into 1at-2nd & then hit 3rd... enjoy the shifting. The PG is something I have considered however for pure longibity/durability. Will it go in place of a TH350 pretty easily?