I knew this trans was dead... TH350 Rebuild

[da_raabi]

Looks like I'm tackling another trans rebuild. Built my first 400 last year, and its going strong in my daily driver C30. So after thoroughly TRASHING this craigslist TH350 in my Camaro, its time for a rebuild.

Symptoms:
1. Its a craigslist tranny. Nuff said
2. End play bad enough to make me lose park: http://www.gmsquarebody.com/threads/th350-wont-engage-park.19992/
3. Loss of third gear, then progressively lost second
4. Nasty nasty squeal in first at higher RPM
5. MASSIVE heat issues. Ended up red-lining the temps on the engine
6. Its a craigslist tranny

7. Did I mention its a craigslist tranny?

So the final death knell was when I took the car to a cruise meet (its first ever) in New Smyrna on Saturday. I knew I had issues (rarely got third gear to engage) but went anyway. Ended up cruising the whole way in second gear, and even that was SLIP SLIP SLIP. Red-lined the temps on the engine, but got there. On the way home it was even worse, but at one point I got it to shift through and hold third, so I FLOORED IT. Just trying to get home. It got me up to about 60-70 then I lost the gear completely. RPMs went up, speed went down.

Sunday we pulled the trans and started investigating. Here's what I found.

1. Previous rebuild only used one check ball, I guess this is a shade tree shift kit?
2. Most clutches were worn and pitted badly. Some looked brand new (previous rebuild was in 2013 according to a date written on the case)
3. Obvious heat problems (you think?). Some steels actually turned blue/purple and the case is darkened (see pic below)
4. Shavings found down around the direct clutch, although I have not yet got the direct clutch out.
5. Two rollers were not being held by their springs in one of the sprags. The springs were completely flattened.
6. Significant debris in the pan and on the magnet. I had cleaned these completely 2 months ago and have probably put only about 20 miles on the trans since then...

This was all found during the initial tear-down. I have not started doing any component tear-downs yet, other than looking at the one sprag.

Here are some initial pics:

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[HotRodPC]

Yep, that one got hot !!!

 

[Derrick]

I think reason 1,6,7 are great points.

 

[ScottyB]

But where did you get it???

 

[da_raabi]

But where did you get it???

Bought it off some guy north of Orlando. What pisses me off is he said it was a good transmission. Oh well, it was $150, so that's not too bad.

I'm looking at about $475 or so for a rebuild, unless I find more issues. That includes a torque converter, rebuild kit, torrington bearing kit, HD 700R4 center support with the wider low sprag, new intermediate sprag with a hardened carrier and a shift kit. Already got a new governor 2 weeks ago that I'll just clean and re-use.

 

[ScottyB]

Bought it off some guy north of Orlando. What pisses me off is he said it was a good transmission. Oh well, it was $150, so that's not too bad.

I'm looking at about $475 or so for a rebuild, unless I find more issues. That includes a torque converter, rebuild kit, torrington bearing kit, HD 700R4 center support with the wider low sprag, new intermediate sprag with a hardened carrier and a shift kit. Already got a new governor 2 weeks ago that I'll just clean and re-use.

Sorry, I was just being a smart ass.

 

[crazy4offroad]

I only used 1 check ball during my TH350 rebuild, makes for harder shifts. Hopefully he left the correct one in lol. I also drilled the separator plate feed holes out to 1/8" to increase line pressure, doubled up the bushings in the sun gear and re-drilled the oiler hole, set up internal dual-feed on the directs, used the hardened intermediate sprag race and hardened input shaft, and used the wider .750" direct drum bushing. But I didn't go as far as the 32 element sprag or milling the direct piston to accept another clutch and steel. It has handed some hot holeshots, and at WOT shifts hard but I mainly run it like that in the dirt. The few times I have ran hard shifts on the street it felt like it was about to twist something in half. But keep in mind the truck's running 38s and 5.13s lol.

 

[da_raabi]

I only used 1 check ball during my TH350 rebuild, makes for harder shifts. Hopefully he left the correct one in lol. I also drilled the separator plate feed holes out to 1/8" to increase line pressure, doubled up the bushings in the sun gear and re-drilled the oiler hole, set up internal dual-feed on the directs, used the hardened intermediate sprag race and hardened input shaft, and used the wider .750" direct drum bushing. But I didn't go as far as the 32 element sprag or milling the direct piston to accept another clutch and steel. It has handed some hot holeshots, and at WOT shifts hard but I mainly run it like that in the dirt. The few times I have ran hard shifts on the street it felt like it was about to twist something in half. But keep in mind the truck's running 38s and 5.13s lol.

Sweet, that's kind of what I'm looking to do. I just don't want to go quite so extreme on the shifts. I want firm, but not harsh. This is a fairly light Camaro so I don't want to bust the tires loose going into third!!

I was planning to leave the check balls in and use a shift kit to do the dual feed.

I've heard of doubling the sun gear bushings, does this mean stacking them? As in push in one extra deep then push in another after it?

What do you mean by re-drill the oiler hole?

I've got access to lathe, so I was thinking about doing the extra clutch. Probably going to skip the hardened input shaft.

This is behind a stock RV-model 454. No mods except long tube headers. I might throw a performer on it down the road, and maybe a cam, but its fun right now so no big plans. I want to make sure this trans holds up. Hopefully my planned mods will achieve that.

 

[da_raabi]

Finally ordered some parts. I'm going for about 75% of the common upgrades. Including:

1. Hardened intermediate race
2. Extra sun gear bushings
3. 4L60E "Turbolator" steels in the low/reverse clutches
4. 5th clutch in the directs
5. Internal dual-feed
6. HD 700R4/4L60E center support
7. Transgo SK350 shift kit

The only things I'm not doing are the Red Eagle frictions, hardened input shaft, and 36 element sprag. Hopefully everything I am doing will help this trans hold up to the big ol 454!

 

[crazy4offroad]

I've heard of doubling the sun gear bushings, does this mean stacking them? As in push in one extra deep then push in another after it?

Yes.

What do you mean by re-drill the oiler hole?

The sun gear has an oil hole that if you double up the bushings the oil hole gets blocked. Re-drill the hole through the bushing by going through the oil hole in the sun gear.

I've got access to lathe, so I was thinking about doing the extra clutch. Probably going to skip the hardened input shaft.

Cool let me know how that goes!

This is behind a stock RV-model 454. No mods except long tube headers. I might throw a performer on it down the road, and maybe a cam, but its fun right now so no big plans. I want to make sure this trans holds up. Hopefully my planned mods will achieve that.

A little more stall on the converter will make it more funner

 

[da_raabi]

Yes.


The sun gear has an oil hole that if you double up the bushings the oil hole gets blocked. Re-drill the hole through the bushing by going through the oil hole in the sun gear.


Cool let me know how that goes!


A little more stall on the converter will make it more funner

Thanks for the info.

I'm looking at a Dacco 10.75" converter with a 1700-1900 stall. I think stock would have been around a 1200 stall, like my truck. Rockauto has this converter (P# B35) for about $70 after the core return. Is that enough stall for my application? Keep in mind this is in a fairly light 80 Camaro with 3.73s and 28" tires.

 

[crazy4offroad]

It might be, since it's a big block. I put in a 2400 and it brake stalls at about 1600 before it starts powerbraking but i expect it to loosen up with use.

 

[da_raabi]

Finished up the dissassembly last night. Getting that low/reverse spring pack out sure is a duzy. Now, I'm not sure if I did this or if it was already like this, but would the retainer being bent like this make the low/reverse clutches burn up? Just trying to understand why this tranny grenaded so bad.

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[da_raabi]

I also discovered that the PO removed the intermediate servo spring. Is that normal for a "shade tree" shift kit?

Completed disassembly pics:

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[crazy4offroad]

That bent retainer sure could have contributed to it, wonder how the hell that happened? All things being equal i would guess the PO did it during install. Whatever method he was using to compress it wasn't applying even pressure. Leaving out the intermediate servo spring is a common mod to make the 2-3 shift much harder but i think there's more to it than just leaving out the spring.