th350 rebuild questions

Transmission to Rear-end

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mdabbott2009
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th350 rebuild questions

Post by mdabbott2009 » Sun Jun 29, 2014 9:14 pm

today I got my 350 took apart from my truck. the direct clutch was smoked. Nothing else in the tranny was tore up. that being said would doing the dual feeding help with this? should I go ahead and machine the piston for an extra clutch for a mild street car? also one more question red altos or borg clutches?

thanks michael

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Re: th350 rebuild questions

Post by Hectori » Mon Jun 30, 2014 2:21 am

For a mild street car, depending of course what mild is, I would not bother with machining the piston. Just go with good rebuilt kit like B&M Master Racing Overhaul Kit or Hughes Performance Transmission Rebuild Kit for example. If you want to pay some extra, get Alto red, but you don`t have to.

Best thing you can do for STREET transmission is to put TransGo shift kit there. You still retain automatic, but can drop to 1 or 2 if you want at any speed. Or you can go with full manual version of that if thats your thing. Or just keep it original shifting, if you are worried about mis shift.

You don`t need to over complicate things, just get quality rebuild kit, with good frictions. replace the bushings. Don`t overlook the bushings, they could bleed off. And just raise the line pressure and increase feed with transgo kit. Of course you can go with other brands with shift kit, but IMO transgo has best one.

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Re: th350 rebuild questions

Post by mdabbott2009 » Mon Jun 30, 2014 8:58 am

The tranny before tear down had a transgo kit in it. The bushings were replaced last rebuild but there trashed the sun gear bushings were the worst.

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Re: th350 rebuild questions

Post by Hectori » Mon Jun 30, 2014 1:27 pm

Transgo sells two kind of shift kits. Actually, another one is reprogramming kit, that actually does what is needed.

Actual shift kit That is type "Corrects/Prevents/Reduces"

Reprogramming kit that is "Street or Full-race; Holds 1st, 2nd and 3rd to any rpm; Backshifts to 3rd, 2nd and 1st at any rpm. Tow & Go and Competition combination."

With that reprogramming kit you have a choice tune it to from street to towing to "full race" kind of deal. I think "full race" is kind of a vague term. It also has dual feed option with it.

Do you know which one did your trans had?

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Re: th350 rebuild questions

Post by mdabbott2009 » Mon Jun 30, 2014 9:06 pm

when installed I didn't have any choices came with springs plate and gaskets and had no other option

this is going in a 4wd 6500 pound truck with a mild bbc if that matters any

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Re: th350 rebuild questions

Post by Hectori » Tue Jul 01, 2014 4:33 am

Sounds to me, that it was just that Shift kit. You will need that reprogramming kit.

With 4wd and big block i would go with th400. It`s much better suited to for use with big block and 4wd. Get one, rebuild it with good rebuild kit and reprogramming kit and you have bulletproof transmission. But you do have to modify driveshaft and transmission crossmember, if you go with TH400, as the case is longer.

But if you want to stay with TH350, you can build it to handle the torque. But i need to know what kind of figures you make with that engine, so i can help you with this.

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Re: th350 rebuild questions

Post by mdabbott2009 » Tue Jul 01, 2014 8:08 am

It's a 461 stock heads 9-1 with a 227/233 it probably makes 425/450tq

I'm kinda stuck with a 350 for now since I've already had drive shafts made.

Truck set up is 34in tire with 410s.

When the truck had a little 355 the tranny always worked great but once I put the big block in it didn't last long.

Would the dual feed option hurt the reverse holding?

I'll prob

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Re: th350 rebuild questions

Post by Hectori » Tue Jul 01, 2014 9:40 am

I think it should hold with the quality rebuilt kit and reprogramming kit set to hd/towing, depending on your driving habits and where you drive it. For a street driven daily driver that doesn`t get beat up(or tow) that much, that would suffice.

But with heavy car with 4wd and big block, i would put a HD intermediate sprag outer race and a extra friction to direct clutch. You should also make sure that the wider bushing is used on direct drum. 0.750 wide if i remember correctly. Bushings should be replaced always, as they are under high loads and if worn out, they will bleed of. Transgo reprogramming kit has double feed feature on it. Those mods would cost less than new rebuild kit, so doing them "just to be sure" makes sense.

You probably know this, but installing extra friction is easy. Just assemble direct drum without seals, put frictions and steels there, and measure how much clearance there is. Then just measure thickness of that extra friction and steel, substract direct clutch clearance from that, and then add about 0.010 per friction.

extra steel and friction thickness - Direct drum clearance + desired final clearance = how much you cut off.

So it would look something like this.(0.098 in.+0.069 in.)= 0.167- 0.040in.+0.050in.=0.177in.

But you must measure it to know how much is to be removed. Then just go to a guy that have lathe, and as him to take that much off from the piston. Piston thickness will be somewhere around 0.66-0.67in.

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Re: th350 rebuild questions

Post by mdabbott2009 » Tue Jul 01, 2014 10:49 am

Hey thanks I'll just go ahead and do extra clutches in it. there's no other way to put more clutches in the rest of it is there?

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Re: th350 rebuild questions

Post by Hectori » Wed Jul 02, 2014 1:31 pm

mdabbott2009 wrote:Hey thanks I'll just go ahead and do extra clutches in it. there's no other way to put more clutches in the rest of it is there?
You need 5 low, 5 direct, 5 forward and 3 intermediate clutches. Depending where your transmission came from, you might have different count of frictions in there. those 5/5/5/3 you can fit there by machining the pistons. And you will be fine with it.

I think it is possible to add more clutches there with modifications, but i doubt that there would be any benefits gained from it.

You can get away with less frictions if you just have sufficient line pressure to hold the clutches.

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Re: th350 rebuild questions

Post by wyrmrider » Wed Jul 02, 2014 2:13 pm

do some searching
for example replacing the wavy with a flat steel
x2 on the sprag- but use manual load when starting with a heavy load
what kills 350s and most trans is hooking up after a water burnout- and you will not be doing that
x2 on the transgo REPROGRAMMING kit
I drove past Transgo yesterday on my way back from Buy Low market (bananas 3lbs/$)
Gil Younger designed kits that had endurance and longevity and still worked well
others shifted harder and broke parts
Git the big transgo kit then call DAVE with the phone number in the kit if you have any questions
there may be options on planetary materiel and number of planetaries but its been a long time since I built my last 350 for a 65 nova

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Re: th350 rebuild questions

Post by Hectori » Wed Jul 02, 2014 2:26 pm

wyrmrider wrote: for example replacing the wavy with a flat steel
I would succest that only on race trans. It is hard on sprag.

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Re: th350 rebuild questions

Post by wyrmrider » Wed Jul 02, 2014 3:05 pm

exactly
that's why he needs to do his homework
lots of mis-information out there that is race/ drag only and breaks parts
BTW I'd never use B&M or Hughes but being down the street from Transgo I'm spoiled
have tried B&M but not Hughes who may have quality at a quality price

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Re: th350 rebuild questions

Post by Hectori » Wed Jul 02, 2014 5:42 pm

wyrmrider wrote: exactly
that's why he needs to do his homework
lots of mis-information out there that is race/ drag only and breaks parts
There are lots of racers giving advices for street transmissions, without realising that true street cars and race cars are totally different deal. And usually it seems to be that street trans can hold up on racing quite good, but racing trans does not survive long on the streets.
wyrmrider wrote: BTW I'd never use B&M or Hughes but being down the street from Transgo I'm spoiled
have tried B&M but not Hughes who may have quality at a quality price
I have B&M kit now on try and i am actually ordering Hughes kit tomorrow. Just trying to find the one that fits best for my needs for performance build. I have used transtar, alto OE and TCI. On a basic stock rebuild, i like the transtar kit the best.

The B&M is the first kit that i will not use Transgo kit, but that is just because B&M has its own reprogramming kit with the set and i want to try that. At the moment i am not that impresset with it.

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Re: th350 rebuild questions

Post by wyrmrider » Thu Jul 03, 2014 7:24 pm

who does the R&D on B&M (or other ) kits?
I can vouch that Transgo does their own
note that when their patents on the Torqueflyte mods ran out other shortly came out with similar valves
who builds B&M converters?
They do use one of the best rebuilders to private label their stuff.
IDK Hughes my impression is that you can't go wrong- quality at a price
you never get more than what you pay for--and vice versa

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