TH350 build [Archive] - Chevelle Tech

: TH350 build


ekacpuc
Mar 26th, 12, 1:25 AM
I've read alot about the TH350 and now think I understand this.. I'm trying to rebuild my TH350 (blown seal and needs work) to handle my 454.



Here's the plan so far and any questions about them:


H.D direct drum and 36 element sprag. A given..

Dual feed. Thats the inner seal that's removed from the direct drum piston? I read the wiki but he just says the seal seperating the two halfs..

Direct piston machined for extra friction and steel (found a source for one ready to go I think..)

Drill 2nd feed to .125" and 3rd .125"-.140". I could just drill em both .125 and be fine? Or should I go slightly larger for the 3rd feed?

Will be using a front planet for a late model (for the roller instead of washer).

Splitting a low reverse friction and stuffing it into the intermediate piston cavity. Do you do this no matter what? Or just if you find your indermediate clutch clearance loose? I don't see where you would measure that clearance so I'm thinkin its just somethin you should do..


Finally the part I'm most unsure about... The 2-3 accumulator. How do you know how long to cut the pipe? My C6 I just threw a #8 nut on top of the existing spring, kinda pre compressed the spring. What way would be ideal?


Also what about the servo for the band? Is there a certain one I should get? Example is my C6 the one that clamps the most is the R code servo..


Greg

NickeyChevelle
Mar 26th, 12, 12:13 PM
:cool: IMHO, pick up a TH400 that needs work (off craig's list, etc.), invest your time and money in the TH400 that you've mentioned for the TH350 you've got, and end up with a stronger TH400...

ekacpuc
Mar 26th, 12, 5:30 PM
Th350 is a strong unit.. Takes less power to turn also. I won't be upgrading... It's sorta like throwing away a good 2 bolt block in favor of a 4 bolt... The 2 works fine.


Hopeing someone knows a little bout trans..

jakeshoe
Mar 26th, 12, 6:29 PM
A TH350 doesn't "take less power to turn" than a TH400.

You can use the nut on the accumulator piston as a spacer.

There is no servo in a TH350 to upgrade.

The seal you want to remove is actually on the drum, and rides on the center of the piston.

Larger feed holes make it shift firmer. .125" on both feed holes is fine.

tonkas69
Mar 26th, 12, 6:48 PM
Question? When you remove the spring from the accumulator and replace it with a spacer do you want the piston all the way down (into the VB) or up against the servo (tranny case).


NVM I found my answer

Between the piston and the e-clip in the VB. I read ur write up Jake. :beers:

ekacpuc
Mar 26th, 12, 11:52 PM
Indeed the TH350 internals wieght more. Takes more power to get em spinning, sorta like using a bigger flywheel. Also the trans itself weights more, thus taking more power to get your rig rolling


I was trying to avoid the whole TH400 vs TH350 debate. I didn't mean to argue with the guy who wrote the article I'm asking questions about.. I simply mean its generally accepted that the TH350 sorta wastes/uses more power due to weight.

ekacpuc
Mar 27th, 12, 12:49 AM
Question? When you remove the spring from the accumulator and replace it with a spacer do you want the piston all the way down (into the VB) or up against the servo (tranny case).


NVM I found my answer

Between the piston and the e-clip in the VB. I read ur write up Jake. :beers:



So we're trying to shove the piston down into the bore? Not hold it open? Confusing, my C6 you just yank the springs and put a pipe where the springs were. Not that way on the TH350?


Greg

steinklatre
Mar 27th, 12, 1:02 AM
I have a TH400 apart right now that were doing a rebuild on if you have any related Q's I can take some pics if needed!

jakeshoe
Mar 27th, 12, 4:10 PM
Indeed the TH350 internals wieght more. Takes more power to get em spinning, sorta like using a bigger flywheel. Also the trans itself weights more, thus taking more power to get your rig rolling


I was trying to avoid the whole TH400 vs TH350 debate. I didn't mean to argue with the guy who wrote the article I'm asking questions about.. I simply mean its generally accepted that the TH350 sorta wastes/uses more power due to weight.

I have some insight into this, that is why I say what I do. There is more to the picture than what the transmissions or internals weigh. So we'll just agree that it is generally accepted by those who don't really know.

I'm not knocking you using a TH350. That is your choice for whatever reasons you choose. They are a pretty decent unit when built right but if you are trying to save a ton of HP as opposed to a TH400, it ain't happening. There are ways you could make it consume less HP, but there are ways to do that on a TH400 as well.

ekacpuc
Mar 28th, 12, 2:17 AM
I have some insight into this, that is why I say what I do. There is more to the picture than what the transmissions or internals weigh. So we'll just agree that it is generally accepted by those who don't really know.

I'm not knocking you using a TH350. That is your choice for whatever reasons you choose. They are a pretty decent unit when built right but if you are trying to save a ton of HP as opposed to a TH400, it ain't happening. There are ways you could make it consume less HP, but there are ways to do that on a TH400 as well.



This isn't helping... My point is, if you stick a fat guy in my truck and drive it then take that fat guy out and stick a skinny guy in it the fat guy uses more HP.


Everything in life is about trade offs. I figured out the answer to my question best I could... Woulda been nice to have the author answer my questions instead of debate th350 vs th400.. You could say I'm wrong any way you'd like but it doesn't change a thing.


You could make a bus run a 1/4 mile faster than heck if you want. Just as you could indeed build a TH400 to "eat" less hp BUT it will always be heavyier.. It's all about money, for me the best bang is a TH350.. There are ways to make the TH350 "eat" even less... Heck there's plenty of 4L80s out there I could use too that'd be "better"..


I'm dissapointed in you frankly for us wasting so much time debating this..


Thanks,
Greg

ekacpuc
Mar 28th, 12, 2:18 AM
I don't mean to sound like a know it all... I don't know it all, but c'mon! What I do know is your replies arn't putting me any closer to a answer to my questions...



Here I was trying to stear clear of a TH350 vs TH400 debate...



I'll just go ahead as planned, I did my C6 without the help of any "pros" and it works just fine.

This was fun but isn't productive.


Greg

jakeshoe
Mar 28th, 12, 4:48 PM
Remove the spring, reinstall the piston in the VB, use a 3/8" nut, 5/16 flat washer, and reinstall the eclip.

Your fat guy/skinny guy explanation is simplified. What if the skinny guy drags the brakes all the way down the dragstrip? I.e. frictional losses.

The TH350 suffers more frictional losses than a TH400.
The parts that matter the most (during acceleration), are just as or almost as heavy in the TH350 as the TH400, so the small weight difference has less effect than it would seem and not enough to overcome the additional frictional losses.
The is why in "most" cases the TH400 doesn't "take more power to turn". The phrase itself is incorrect.

You made an incorrect statement. I corrected it, not necessarily for your benefit, but others who read here.

wes69ss
Mar 28th, 12, 8:55 PM
i've read alot about the th350 trans and i THINK i understand this. just because you read something doesnt make it 100% fact. good people on this forum are giving you good advice and you want to get into a pi$$ing contest. you are argueing with guys that have built these trans and not just read about them on the net. Wes, trans builder since 1982

tonkas69
Mar 29th, 12, 3:26 PM
Ok so if you lock down the accumulator piston down is it necessary to install the band and just leave the servo free floating in its bore.

rkd
Mar 30th, 12, 12:08 AM
Thread hijack!

A TH 350 weighs more than a TH400?