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Old 12-06-2011, 06:49 PM
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T-350 rebuild (have problem)

Hello all and thanks in advance for taking the time to view my issue.

A buddy of mine asked me to rebuild his TH350 in a 70' model Chevy C-10. Since I've successfully built 7 or 8 for myself and others I agreed.I am a pretty good hand with a wrench but by no means a transmission tech! Watch how it comes apart,reassemble in reverse order. Not to mention the first two I ever did was under the supervision of someone who did know what, how and where. This person sadly has past and therefore I have lost that resource.

The truck has sat for about 10 years and he reported to me the transmission just quit pulling when it got parked. I figured okay, I can handle this... well I've had it apart twice now and am still scratching my head.

Yes, I installed a master kit, all seals replace, all new clutches, measured pump wear and looked for over heating, worn thrust washers, bushing and meticulously cleaned every valve, spring, part and case.

Installed the transmission, checked that it took reverse and drive, they do and pickup immediately.

We started our test drive and it made it's first shift at about 23 mph WOO HOO were running good! Waiting for the second shift at 35 or 40 and absolutely nothing. The rpm keeps climbing and we keep picking up speed but no last shift.... ever. I readjusted the kick down. I disconnected the kick down. No change. I tried letting out of the gas abruptly and getting back on it, nothing.

I called a friend who works at one of the local tranny shops and explained this. He said it sounds like it's in the governor. I pulled the governor, the valve moves, no broken springs, and the weights have freedom of movement. Tried it, same thing. I even replaced it with one from a donor transmission. No change.

I removed the transmission the second time, removed everything again, pulled the pulled all the clutch assemblies down again, made sure I didn't cut any seals. Put it all back together installed it, and still the same issue.

It seems that it is starting out in 2nd? Although in the same breath it seems as though it isn't shifting into high based on the rpm of the eng. Here is why I say this.

Starting in D1 and manually shifting into D2 it shifts as advertised. Shifting from D2 into D3 there is no shift. However if you shift from D3 back to D2 it down shifts. Then you shift from D2 to D1 and you get another down shift. It's driving me crazy!

Alternatively if you start out in D3, you get one shift at about 23 mph, then no shifts all the way up to 55. But if you slow to 40 then shift to D2 it does down shift and again slow to about 25 and shift from D2 to D1 it down shifts again!

Additional note: When in low every once in a while it sounds like something is grinding very quickly and then it stops. It may do it 2 out of 5 times when shifting down into low. Also it seems to do it when you say hold the shift lever in a way you would be overtraveling the linkage. When I had the tranny apart the 2nd time I specifically looked for metal in the pan, found non. I looked for obvious chaffing or grinding marks I saw none. After the second installation and test drive it replicated the noise twice.

Forward gearing picks up immediately and seems strong through full acceleration. Reverse gear picks up immediately but seems somewhat sluggish to me but does backup.

Anyone who may think they know what I'm up against please please give me a clue my friend will absolutely appreciate it and I will as well.... I figure the tranny is coming out at minimum once more I would love to make it the last.

Thanks!

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Old 12-06-2011, 07:11 PM
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Modulator hooked up and working (sorry- had to ask)?
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Old 12-06-2011, 07:38 PM
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Check the Gov feed holes & Screen?
Pressure Test?
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Old 12-06-2011, 08:13 PM
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Quote:
Originally Posted by Vellmen
Hello all and thanks in advance for taking the time to view my issue.

A buddy of mine asked me to rebuild his TH350 in a 70' model Chevy C-10. Since I've successfully built 7 or 8 for myself and others I agreed.I am a pretty good hand with a wrench but by no means a transmission tech! Watch how it comes apart,reassemble in reverse order. Not to mention the first two I ever did was under the supervision of someone who did know what, how and where. This person sadly has past and therefore I have lost that resource.

The truck has sat for about 10 years and he reported to me the transmission just quit pulling when it got parked. I figured okay, I can handle this... well I've had it apart twice now and am still scratching my head.

Yes, I installed a master kit, all seals replace, all new clutches, measured pump wear and looked for over heating, worn thrust washers, bushing and meticulously cleaned every valve, spring, part and case.

Installed the transmission, checked that it took reverse and drive, they do and pickup immediately.

We started our test drive and it made it's first shift at about 23 mph WOO HOO were running good! Waiting for the second shift at 35 or 40 and absolutely nothing. The rpm keeps climbing and we keep picking up speed but no last shift.... ever. I readjusted the kick down. I disconnected the kick down. No change. I tried letting out of the gas abruptly and getting back on it, nothing.

I called a friend who works at one of the local tranny shops and explained this. He said it sounds like it's in the governor. I pulled the governor, the valve moves, no broken springs, and the weights have freedom of movement. Tried it, same thing. I even replaced it with one from a donor transmission. No change.

I removed the transmission the second time, removed everything again, pulled the pulled all the clutch assemblies down again, made sure I didn't cut any seals. Put it all back together installed it, and still the same issue.

It seems that it is starting out in 2nd? Although in the same breath it seems as though it isn't shifting into high based on the rpm of the eng. Here is why I say this.

Starting in D1 and manually shifting into D2 it shifts as advertised. Shifting from D2 into D3 there is no shift. However if you shift from D3 back to D2 it down shifts. Then you shift from D2 to D1 and you get another down shift. It's driving me crazy!

Alternatively if you start out in D3, you get one shift at about 23 mph, then no shifts all the way up to 55. But if you slow to 40 then shift to D2 it does down shift and again slow to about 25 and shift from D2 to D1 it down shifts again!

Additional note: When in low every once in a while it sounds like something is grinding very quickly and then it stops. It may do it 2 out of 5 times when shifting down into low. Also it seems to do it when you say hold the shift lever in a way you would be overtraveling the linkage. When I had the tranny apart the 2nd time I specifically looked for metal in the pan, found non. I looked for obvious chaffing or grinding marks I saw none. After the second installation and test drive it replicated the noise twice.

Forward gearing picks up immediately and seems strong through full acceleration. Reverse gear picks up immediately but seems somewhat sluggish to me but does backup.

Anyone who may think they know what I'm up against please please give me a clue my friend will absolutely appreciate it and I will as well.... I figure the tranny is coming out at minimum once more I would love to make it the last.

Thanks!
i would say that you have a problem with either the direct clutch drum or you have a problem with the pump or sealing rings that go to the direct drum.
the shifting you feel when you drop in into manual 2 is nothing but engine braking, when you put the trans in manual 2, it applies the band. the reason you dont feel anything in drive is because it should have engine braking in 3rd and youre not getting 3rd.
the direct drum is on for both 3rd and reverse.
thats all i can think of at the top of my head, maybe theres someone else who might have some additional info that can/will help.
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Old 12-06-2011, 10:40 PM
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Thanks for all the info and questions.

Yes the modulator is working and was replaced.

Yes the governor passageway is clear and open. (removed the micron filter on second tear down)

No, I did not pressure check. How and what should I have pressure tested? The drums?

Direct drive drum, the one that was in the rebuild had the brass bushing worn pretty badly (no brass left) I pulled another Direct drive drum from a donor that had a much better bushing. However in mentioning of the sealing rings... it seemed as though when installing the pump I had ZERO problem getting the rings through the center of the drum. If memory serves me correctly I thought I remembered having trouble getting those to install as the pump is being set. This was not the case and I passed it off as my memory failing.

So, if they should fit tighter (seal better) and they are not are we on the right track? Is it possible the bushing in the drum even though it appears in really good shape a root cause? Can this bushing be replaced?

Any more suggestions?

Thanks: tnsmith10, SSedan64, and cobalt327

I really appreciate your time.
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Old 12-07-2011, 05:44 AM
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Quote:
Originally Posted by Vellmen
Thanks for all the info and questions.

Yes the modulator is working and was replaced.

Yes the governor passageway is clear and open. (removed the micron filter on second tear down)

No, I did not pressure check. How and what should I have pressure tested? The drums?

Direct drive drum, the one that was in the rebuild had the brass bushing worn pretty badly (no brass left) I pulled another Direct drive drum from a donor that had a much better bushing. However in mentioning of the sealing rings... it seemed as though when installing the pump I had ZERO problem getting the rings through the center of the drum. If memory serves me correctly I thought I remembered having trouble getting those to install as the pump is being set. This was not the case and I passed it off as my memory failing.

So, if they should fit tighter (seal better) and they are not are we on the right track? Is it possible the bushing in the drum even though it appears in really good shape a root cause? Can this bushing be replaced?

Any more suggestions?

Thanks: tnsmith10, SSedan64, and cobalt327

I really appreciate your time.

if you bought a master overhaul jit then, the kit should have come with new sealing rings for the pump and the 1-2 accumulator. and they are metal rings.
one thing id look at is the input drum where the sealing rings go and make sure the drum isnt "cut" where the rings ride. also, depending on how bad the bushing was on the drum may also point out damage to the bottom side of the pump where it goes into the direct drum.
air checking clutch packs and drums is essential in making sure that the trans will be hydraulically sound for operation. it may be possible that you cut a lip seal when installing the direct piston or, the thought of maybe installing a lip seal backwards comes to mind.
its easiest to air check the direct drum while its sitting on the pump before installation.
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Old 12-07-2011, 05:33 PM
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Much thanks for the reply,

Yes I did install the new rings, 1-2 accumulator looses me.

I am pulling the trans tomorrow and will pull the pump and direct clutches and drum. I will inspect the items you mentioned.

Cut seal? Maybe, doubtful I was very careful.. backwards? lol more possible than cut in my opinion. I will break the drum back down and look.

I have a compressor (25 gal) and an air chuck for airing tires, and a air nozzle for blowing air. Is there a shade tree method of air checking the drum? I assume I attempt to induce air at the check ball?

Thanks again
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Old 12-07-2011, 07:51 PM
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Quote:
Originally Posted by Vellmen
Much thanks for the reply,

Yes I did install the new rings, 1-2 accumulator looses me.

I am pulling the trans tomorrow and will pull the pump and direct clutches and drum. I will inspect the items you mentioned.

Cut seal? Maybe, doubtful I was very careful.. backwards? lol more possible than cut in my opinion. I will break the drum back down and look.

I have a compressor (25 gal) and an air chuck for airing tires, and a air nozzle for blowing air. Is there a shade tree method of air checking the drum? I assume I attempt to induce air at the check ball?

Thanks again
i mentioned the sealing rings because with your current problem, it made me wonder if you changed them. i was basically providing info on the rings that should come in the kit the 1-2 accumulator rings are part of the kit where as you will notice that the sealing rings were not provided for the band apply servo in the case or for the 2-3 accumulator. (depending on the kit. transtars kit does not come with them).
anyways, back to your trans.
to air check the drum, take the pump and sit it upside down through a hole on a bench or a large coffee can will work. place the direct drum on the pump as if it were in the trans. there are a few round drilled holes on the pump where the pump gasket goes. with you blow gun, start applying air to the holes. you should be able to hear and see the clutches apply in the drum if everything is right.
theres 4 or 5 holes in a row, to verify which is for the direct drum, put air through the holes first before putting the drum down and put air through the holes till you find which one it is.
once you find which one it is and test the drum, you will be able to find at that time whether you have a problem in that drum or not or, if its a sealing ring or, if theres even a problem there in the first place.
with the 350's you say that youve built so far, i dont think youll have a problem figuring out what i explained above, if you do, ill see what i can do on putting a pump and drum together and take some pics for you.
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Old 12-07-2011, 08:07 PM
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Thanks for the info on testing the direct drum. Pictures shouldn't be necessary, but I'll let you know. Is there a way for me to test the intermediate drum?

QUOTE: band apply servo in the case or for the 2-3 accumulator END QUOTE

This ring was also provided in my kit and it was installed.

Back to the direct drum... is it safe to assume if the clutch does not actuate, and I disassemble the drum and find all the seals intact and installed correctly the issue is with the rings? If so what should I be looking for to correct the issue?
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Old 12-07-2011, 09:15 PM
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Quote:
Originally Posted by Vellmen
Thanks for the info on testing the direct drum. Pictures shouldn't be necessary, but I'll let you know. Is there a way for me to test the intermediate drum?

QUOTE: band apply servo in the case or for the 2-3 accumulator END QUOTE

This ring was also provided in my kit and it was installed.

Back to the direct drum... is it safe to assume if the clutch does not actuate, and I disassemble the drum and find all the seals intact and installed correctly the issue is with the rings? If so what should I be looking for to correct the issue?
there is no drum for the intermediates, theyre applied by the piston in the backside of the pump.
if youre talking about the forward/input drum, it also can be tested through the pump as well. just put the direct and forward drums together and then slide the pump down over them.
as far as the air testing goes, you should be able to see and hear where the leak is. especially if things are still wet with fluid. the wet air test will show bubbles where the leak is.
if the seals are in fine and you cant see or feel any problems with the sealing rings and the drum is not ring cut, then start checking for a crack in the backside of the pump that the drum rides on. (stator)
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Old 12-07-2011, 10:10 PM
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im willing to bet u got the 2nd gear clutch cleaence to tight if u do it will take off in 2nd go to 3rd but if u use manual low it will bind and make a horrible noise also did u replace at the intermediate sprag u might have one to many clutches in the 2nd gea pack
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Old 12-10-2011, 04:21 PM
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okay, I'm back for some more of your guys professional help!

We got the tranny out today and tore back down.

I was asked to check the sprag installed inside the low reverse roller clutch. It was in properly and completely seated. I was asked if I thought the low reverse clutch stack was too tight. It seems free, there are 5 rotors, as the TH350 parts break down I have indicates.

I was also instructed on "pressure checking" the direct drive drum. The direct drive drum will not move. It did once... it pumped out like 3/8" and after that when trying to move it again it only moved like 1/8". I inspected the drum, it has wear from the pump rings. So I used another direct drive drum which doesn't have ring grooves. It won't move at all now. I was using 40psi, and the intermediate clutch ring moves smoothly and every time. The forward drum also moves easily with 40 psi. I cranked the pressure up to 90psi and tried the direct drum again, it still won't move.

We took it down, and examined the 3 seals in it. They all look fine. Now I must ask. The inner most and the outer seal both face toward the drum? The middle seal faces opposite right? Hope so because that's how they look they should go.

So at this point I assume I am losing my pressure at the rings? I installed the new ones that came with the kit. I have them properly locked and the points where they lock are staggered like when installing rings on a piston.

I even soaked the rings and bushing with trans fluid. Should I put fluid under the pressure plate in the drum?

Again thanks and hope someone can help!
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Old 12-10-2011, 07:27 PM
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When air checking a clutch , the whole clutch pack should be assembled so the piston is not moved too far and damage a seal or the spring retainer.

If you are putting 90psi to the direct drum clutch via the pump / stator support, where is the air going to? Is the air rushing out a leak or is the air pressure held solid with no leakage?
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Old 12-11-2011, 11:10 AM
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it's leaking out

I started with 40psi, I only went to 90 to see if it were the sprigs I wasn't over coming. You can hear the air leaking out at both pressures
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Old 12-11-2011, 04:35 PM
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Well I believe I found the problem. At least I hope so I have reassembled the tranny and will put it in tomorrow.

I pulled the direct drum apart again, don't know what made me do this but I added an ounce or two of fluid inside and reassembled it.

I did a pressure check, it moved out, then back in and wouldn't move again. BUT, I noticed fluid coming out by the springs. I pulled the spring assembly again and removed the drum piston. Upon examination I found it cracked, not a small crack but about 1/3 of the way around it. Hairline at best but crack non the less.

I installed a piston from the donor drum and the drum piston moves as advertised now! Hopefully problem solved!!!

I want to say thanks to you all for your ideas, suggestions and comments. Due to your suggestions you helped me zero in the problem! Thanks again!!
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