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Old 09-22-2003, 05:22 PM
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Angry My band is fine

Guess I'm in for a real challenge now. Heres one post about it...
Heres another one, these both decribe the problem.
The band has .026 of smooth material on it, nothing broken, the rear servo piston seal looks a little rough, like some shavings were all over it.
Not enough to be obviously blown. The direct drum looks a little worn where the center support sealing rings ride.

Still have a lot to check over if anyone can add some key spots to check as to why it would lose reverse completely, have no engine braking in manual first and have 400 psi line pressure in reverse at 2200 rpm I would be more than happy to hear about them. Third gear works ok, in fact all forward gears work perfect.

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Old 09-22-2003, 05:43 PM
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4l80e no reverse

replace the band , if you have another band compare them. Jason you said it shudder in reverse but third was ok, and that comes in low gear engine braking as well the only thing that makes any sense is the rear band or the piston that apply's the band if direct drum shows wear you should change the drum and rings to the late style (rings) you might even change the center support wear a lot in early unit. best ideas I have with out being there to see what you have......
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Old 09-22-2003, 06:56 PM
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Quote:
best ideas I have with out being there to see what you have......
I know what you mean and I do appreciate your efforts in helping me this far
I did put the low gear and band back in along with the servo and air checked it. It seems to have a strong grip and it holds using 90 psi. No leaks.
I checked the direct seals too, they're ok.

One thing I found that I don't like is the very end of the input shaft in the trans where there are two teflon seals, this looks ok but the bore it goes into ?(EDIT PART 3301 HERE) looks like it has been machined about four different sizes inside. Hard to explain, doesn't look like wear but I have a feeling it's not supposed to look like this. The sealing rings are slightly concave and there doesn't appear to be a smooth spot for them to ride on.
Not sure which of my trans' sympoms this would cause maybe no (noticable) lock up?
Sorry for not knowing the proper terminology and names of parts.

BTW after I did the pressure test and stall tested it in reverse to 2000 rpm and the pressure went up to 300 psi, the truck has not even tried to move in reverse, it doesn't even seem to take up driveline slack where as before it would shudder but at least move.

All I have are three old rough (grooved?)style th400 bands, would these work or does it need the smooth band?

Last edited by Jason; 09-22-2003 at 08:39 PM.
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Old 09-23-2003, 04:07 PM
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Airworld, what do you think of the high line pressures it had in reverse?


Quote:
I took some pressure tests to make sure everything else is ok, it slips in reverse, here are the results. All readings taken in reverse.
120 psi at 700 rpm.
180 psi at 1000 rpm.
400 psi at 2000 rpm while it's trying to move in reverse.
Heres what I thought was odd after the above test it stopped trying to move in reverse and the pressure would go up to 450 psi at 2200 rpm and then shoot down to 350 psi.
I'm trying to get as many opinions as I can, even if you are correct with the band being bad, it still has a problem and that is the high pressures in reverse only, normal in every other range.
Thanks if you choose to relpy if not it's ok too.
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Old 09-23-2003, 05:38 PM
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band is fine

checked with our other shop for answer, there thoughts or best guess is that the piston that apply the band is cracked .crosley said valve body trouble if all things check out ok replace valve body?????
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Old 09-23-2003, 07:18 PM
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I disassembled the whole rear servo piston, unlike a th400 this one has a spring at the end between the pin and piston, looks like to cushion it's apply.
All the parts look ok, like I said I put the gear train up to the reaction carrier and rear band back in the case and installed the rear servo and air checked it at 90psi.
I pressed the air nozzle valve once and the band applied fast and tight and held until I removed the nozzle, when I removed it a lot of air pressure came back out, while it was pressurized it was not leaking.
My thoughts are a hydralic leak somewhere between the pump and reverse servo.

I thought the boost valve Crosley was talking about is in the pump.

Anyway I talked to my usual converter shop and they have a guy next door who works on a lot of 4L80's from the converter internals back- the whole thing. I guess I'll go bug him, see what he says.
Thanks for your help



Quote:
Sonnax has a nice replacement boost assembly
I was thinking of getting a transgo SK4L80E kit described as ---# 46930 SK 4L80E New extreme quality boost bushing with matching boost valve. Corrects/Prevents/Reduces: High pressure parts breakage; has boost valve and pressure relief valve; direct clutch burnup; soft 2-3 slide-bang 1-2; low pressure due to solenoid filter breakup; no upshifts without diagnostic codes.
Ever install one?

Last edited by Jason; 09-23-2003 at 07:18 PM.
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Old 09-23-2003, 07:30 PM
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Quote:
Originally posted by Jason
I was thinking of getting a transgo SK4L80E kit described as ---# 46930 SK 4L80E New extreme quality boost bushing with matching boost valve. Corrects/Prevents/Reduces: High pressure parts breakage; has boost valve and pressure relief valve; direct clutch burnup; soft 2-3 slide-bang 1-2; low pressure due to solenoid filter breakup; no upshifts without diagnostic codes.
Ever install one?
the Sonnax valve has a built in relief valve #34200-10K

The transGo stuff is top quality. I was told by a friend the Sonnax valve lasts longer , less wear than the TG unit. Read the instructions 3 times , then start on the tranny.

TG does the pressure release differently from Sonnax to avoid the parts breaking pressures.

Yes you must have some cross leaks . You mentioned the sealing ring area being worn out.

Any valves stuck in the vb?
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Last edited by Crosley; 09-23-2003 at 07:45 PM.
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Old 09-23-2003, 08:06 PM
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Any valves stuck in the vb?
No.
The only things I find questionable are the parts I tried to describe before. The end of the input shaft, inside the trans, has two teflon seals on it, all thats ok but the area that these seals ride on are grooved up pretty good. Doing a pressure test on this it seems to be part of the forward clutch circuit, very little leaks out from this area and the forward applies.

Other than that the gaskets are very brittle, no signs of crossleaks anywhere including the pump.
The boost valve (in the pump) seems to have a ridge in the sleeve, it catches very slightly.
Thats all I've seen and I've looked everything over and cleaned parts for about 4 hours, nothing else wrong

Quote:
Yes you must have some cross leaks . You mentioned the sealing ring area being worn out.
Slightly more than what I've seen, I have a brand new 4L80 drum somewhere, hopefully I didn't use that in my nova. Would a th400 sprag type drum interchange ( I would figure it would).
The bushings towards the front of the trans including the center support are shot too.
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Old 09-24-2003, 08:34 AM
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double check the stroke on the rear servo. we have welded on to the apply pin when the servo had to stroke too far.

I think you know the differnece of the drums. The race is wider.
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