Technical TH350 lost third gear - binding?

I did..... I'm guessing that's a problem? Care to fill me in?

 

B&M kit should basically be a plate. It’s fine. When I did mine I just drilled the plate and duel fed the direct clutch in the drum. Shifts firm not hard. That’s all I wanted. Some of the kits shit too hard.


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I have never been a big fan of there shift hits. My personal choice is TransGo.

 

So I found the B&M at Advance Auto on clearance for 12 dollars. I thought it was worth a shot! I'm hoping to start on it after work tonight if all goes well.

 

You know I got to thinking about your problem. If the problem is the 2nd overrunning clutch stuck, it would start in 2nd gear when you put it in drive. You wouldn't have a first gear. If it didn't hold, you wouldn't have second.

I took a good look at the hydraulic diagram and found something that I vaguely remembered. The 3rd gear clutch has two apply areas. In 3rd gear it uses the smaller apply area, in reverse it uses both apply areas. If the lip seal that separates the two areas were to fail, there is a path to try to apply the reverse clutch. If you don't find a hard part failure causing the problem, I would take a close look at the lip seal in the center of the 3rd/rev clutch.

 

No it would not be starting out in 2nd gear, the intermediate clutches are not applied in 1st. And also no to the center oil seal in the direct drum causing the problem.

Bill

 

You can leave the center seal out of the direct clutch drum with no problem. Just makes the surface area to apply the clutch bigger. I did that on mine. You do have to plug a hole in the plate though or it can cross leak. I suspect he has a cross leak around a check ball. Possibly the plate is damaged from the ball hitting it.


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Yes, you are correct. That also points to the possibility of binding in high if the overrunning clutch were bound up.

 

Alright. Got it apart. I noticed this "hole" above the shifter. Is this supposed to be there?

Also there's a bunch of crud in the oil and on the filter.

 

Also support plate has indentions around 2 bolt holes.

 

your sprag is gone, pull it out

 

Yeah that’s a lot of metal!


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I went ahead and put the shift kit in it so I could still move it around. No improvement.

I'll be pulling it this winter.

 

So it has been a long time since I posted, but I thought I would come back and wrap this up. The trans ended up having an exploded sprag on the intermediate section along with a ton of other janky stuff done to it. I found missing wave plates, missing springs in the valve body and a bolt stuck in the 1-2 accumulator cavity. I don't know how the trans lasted 25 years like this!

Just thought I would share.

 

Glad you came back with an update. Might be a good time to look for a 200R4 as a replacement.

 

If it's NOT a busted sprag, then it ate the direct clutches; welcome to the TH-350 transmission. They also have a tendency to actually break the bell-housing, but that's not the issue here. Your support plate has been off and on a few times (why the bolts have sunk into the plate); some shift kits come with a new one (has a new fluid path machined into it) that's installed under the old one; it's the easiest way to dual feed the clutches, without getting into the transmission. Your transmission needs a rebuild; time to pull it out. I am Butch/56sedandelivery.

 

You can leave the wave plates out, especially in the high drum, as long as you add a steel or so to correct the clearance. Makes it shift firmer. I usually put the one back in the forward clutch so they don’t engage so hard. As for the bolts, I stuff bolts in all kinds of valves. Bolts, nuts, whatever I can find that is the right length. LOL


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They were essentially "bypassing" all the factory, "soft shifting" characteristics with those mods. I remember guys used to stick a section of broom handle in the accumulator; the factory spring would frequently break. I am Butch/56sedandelivery.

 

Stuff wears out. Just ask "your boy Ice T".

I lunched a tranny in something just the other day. No warning it just went. There are two things you can do, one is open it up and repair it the other is replace it. If you open it up let us know what you found.

 

oh boy
I feel another one of my funny racing stories coming on...
That reminds me of something in my drag racing days.
On a super tight budget, I rebuilt a th350 for the race car, and bought a transbrake kit for it.
Ok. Ran great.
Worked great.
After quite a few races (2seasons? 3?), the tranny still felt good so we decided we didn't need to freshen it up quite yet.
Well,
When the trans brake is engaged, it pressures the Reverse clutch and the Drive clutch, thereby locking the trans.
You stage with Direct, Low, and Reverse all engaged.
When you let go of the button, reverse lets go, and you get a surge forward for a great launch in low gear.
Ok so far.
My buddy did his burnout.
Stage.
Lock the trans.
Tree starts counting.
Rpms about 4,000 with pedal to the floor.
Turbo spooling up.
Ready.
Direct clutches start to slip at 20lbs boost.
Just barely before Green, the car starts to back up as if it wanted to go somewhere else.
It was hilarious, and it must have looked quite odd to the crowd in the stands.
Oh well, that's racing. at least it was for us.


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