[Cliff R]

Here's something to ponder on. In the TH350 and the TH400, the low roller sprag NEVER gives any troubles. It is not any larger or stronger than the intermediate sprag, which is known to be a "sore" spot in both units. Why doesn't the low sprag fail in high HP applications.......maybe because it isn't involved with an extremely "hard" 1-2 shift? I can guarentee this, if you have a manual valve body and ALWAYS started in second gear, you wouldn't be able to break the "weaker" roller clutch, let alone the 34 or 36 element sprags..........Cliff

[Bumper]

Here is a picture of a bolt in center support.

[Bumper]

Originally Posted by Cliff R

Here's what we include here to prepare the TH350 for serious applications.

Full set of bushings
Full set of thrust washers, including selectives
4L60 bolt in center support
4L60 low/reverse sprag with long rollers
Hardened intermediate sprag race
New intermediate sprag
5 forward frictions/steels (Raybestos or Borg Warner)
5 low/reverse
5 direct (machine the apply piston for one additional friction/steel)
3 intermediate (leave the waved apply plate in service)
New band
New filter
New seals
New gaskets
New sealing rings
Transgo shift kit (high performance)
One peice carrier over the front planetary (if it came with a 2 peice unit)

Retain all the new bushings with red loctite. Air test all the clutch packs on the bench, on the pump inverted in a vise, and again once the unit is assembled. Set the shaft end play to about .010-.020". Check all sealing ring surfaces for scoring, wear or damage. Check both planetaries for excessive play at the pinions. Check all torrington bearings for rough or tight spots.

The kick down cable is not needed, tap the hole in the case for an NPT plug. Soak all frictions overnight before assembling the drums. No "special" or "high performance" frictions or steels are required, but never a bad idea if you don't mind the extra cost. Do not disable either accumulator, new HD springs are never a bad idea.

TH350's are tough units, but the cases are weak at the bellhousing area. Correct pinion angle is a must, and NEVER use a solid mount on the rear of the transmission....Cliff

Thanks Cliff Ruggles for sharing that, you're book on Q-jets is killer and is a total bargain for all the info it has.

[Cliff R]

Thanks so much. We are nearly finished with our second book, it's on the 4L60 and 4L60E transmissions. I'm finding it quite a challenge compared to the Q-jet book. Quite a bit more complicated, as transmissions are quite complex in comparison to carburetors. Hoping to have it finished up pretty soon.....Cliff

[bad69bird]

Originally Posted by Bumper

In post #1 he stated 450 horse so all that would be needed is the 20 dollar intermediate sprag race ?

...and read the rest of post#1...specifically the second to last sentence. "Will my torque eventually destroy my tranny?"

I was giving an example of how a well built T-350 WILL survive a high HP/TQ motor.

[Indian Uprising]

Thanks for all the help!!! dont mean to ruffle any feathers... my car is current a 450hp app. haven't been running it long... Started street strip but now its race only... so I am already looking down the road at the next combo... the 650HP... damn racing is freakin' addictive (my only problem has been all this rain we've been having)

I just want to see if you guys have th350s living in the 9-10sec range.

Thanks for all the help!

and Pontiacdude I'll be coming to you for my future engine builds!

[firebirdcrazy1959]

I raced my car with a T350,it went bad from sitting 5 years[would not work one day],then i put in a "rebuilt"350 from a guy.One day after coming out of the gas station i punched it hard from 1-2 then let off before 2-3.After that now it makes a clicking noise in 3rd gear?I'm just going to use a PX code T400 i had in my 70 Firebird when i put the 462 in the 81 SE.I like the T350 better but don't have any more.I have 3 T400's.I guess i can get both T350's fixed also.

[NHRASuperStock455SD]

Originally Posted by Bumper

A TH350 can handle 600 horse and 600# of torque with only a hardened intermediate sprag race, dual feeding of the direct clutches and adding one additional steel and clutch to the direct drum. Also the 2-3 accumulator can be modded with a shim or just block the 2-3 feed in the valve body to catch a firmer 2-3 shift.

Use of standard intermediate roller clutch is underrated in a TH350. The sprag type 36 element is generally considered stronger, mostly because it has more elements so greater contact area, more evenly spread around the diameter of the race. But they can roll over as we know. The lowly roller type element may have less contact area but it actually has to BREAK the race to fail.

The TH350 has a bit of a bad reputation due to people using shift kits that hit the hard parts with a lot of shock and using low capacity cores.

You can take what Bumper said to the bank on this! I think TCI sells these sprags in a kit form. All future 350's will get them from us. We destroyed the 8 roller sprag way too many times, and yes we took off in 2nd gear in the burn outs. If a 400 6X motor blows them in a light car, then just think what our big motor would do. They only lasted 2 runs, and we broke it 4 times last year. After installing the 36 roller sprag tons of runs, no troubles.

Lynn

[Cliff R]

Lynn, did you destroy the outer race, the sprag, the drum, or all of it?

The aftermarket "hardened" outer race is sufficient for most builds. For serious work the TCI 36 element sprag and drum are preferred. They basically install a smooth hardened inner race onto the drum, then add a 36 element sprag clutch, and hardened outer race. Very similiar to the set-up used in the TH400 transmissions to replace the roller type sprags.

Once the 36 elements sprag set-up is installed, the only way it can fail is to roll it over, or break the snap ring and push it off the drum, the same way they fail in TH400's.....Cliff

[PONTIAC DUDE]

You can put the ..when is it time to step up to a T-400 over a T-350 in the same catagory as............ the how much will a Pontiac block take before you need an IA II block.

Just different hp levels comparing the tranny deal to the block deal........... or is it?



They also race T-200 too, but ........

[NHRASuperStock455SD]

Originally Posted by Cliff R

Lynn, did you destroy the outer race, the sprag, the drum, or all of it?

The aftermarket "hardened" outer race is sufficient for most builds. For serious work the TCI 36 element sprag and drum are preferred. They basically install a smooth hardened inner race onto the drum, then add a 36 element sprag clutch, and hardened outer race. Very similiar to the set-up used in the TH400 transmissions to replace the roller type sprags.

Once the 36 elements sprag set-up is installed, the only way it can fail is to roll it over, or break the snap ring and push it off the drum, the same way they fail in TH400's.....Cliff

Cliff,

All of the above. Jim Paquet tried every trick in the book to make it work. The only thing that will hold the power is the 36 roller. JPT does not buy his from TCI, he builds his own. Kenny Shawver said there is no way a 8 roller sprag will hold a SS engine. Even a 6X motor. After 4 tries, the modified unit had a max life of 2 runs. With the 36 roller we have had at least 25 runs without a failure. It is definitely the weak link for the 350T.

Another item has cropped up over the years and that is that some guys have trouble with cracking the bellhousings. Many machine off and use the aftermarket, but we have never had any trouble. John Angeles and Bill Eadelis both broke theirs. Don Kennedy, my brother, Phil Monteith and I have never broke one. Must be the way we mount it or the car.

Your list looks good, but if you have over 500HP I would definitely do a 36 roller sprag.

Lynn

[Cliff R]

Lynn, the outer race is typically the failure point for the TH350 roller clutch. They also do not like to be "shocked". I was told several years ago by an "old timer" to only use one clutch for intermediate, and leave the waved apply spacer in place, and do not disabble the accumulator. Never tried it, but the logic is sound.

We leave the accumulator in place, and the waved apply spacer, use 3 clutches, hardened outer race and have never broken one. The 36 element sprag clutch units only advantage over the roller sprag is evening out the pressure over greater surface area. The roller clutch must break to fail, the 36 element sprags can be "laid over" and fail as well.

The life expectancy of a TH350 at the bellhousing area, when the pinion angle is WAY off, a solid rear mount is used, and/or excessive chassis flex is about half a dozen runs!.....Cliff