'93 4T60E - Same trans, different prob - Slips in low/reverse after rebuild - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-26-2007, 08:58 AM
mjw mjw is offline
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'93 4T60E - Same trans, different prob - Slips in low/reverse after rebuild

Greetings all,

I finished rebuilding the 4T60E mentioned in an earlier post. Many thanks to airworld2 and the others that replied to that thread. Now I have a different problem with this thing. After the rebuild, it slips in low and reverse, unless I disconnect the vacuum modulator line. (valve is not sticking/modulator is new). Up and downshifts are fine, TCC lockup is fine, and it's not making any noises. There is no slip or shudder in 2nd, 3rd, or 4th and no trouble codes are set (not even an 1870, which is odd).

I was extremely cautious during reassembly, and am positive that I don't have any cut lip seals, damaged clutch pistons, excessive clearances, etc. All seals, sealing rings, clutch pistons, steels & frictions were replaced, as were the vanes in the pump (which was fine, by the way). Everything is torqued, and I air-tested everything during re-assembly and all clutch-packs and servos applied and released properly. Also replaced the TC (and pre-filled it before reinstallation) and flushed the cooler.

As a sanity-check, I took hundreds of 'before-and-after" photos to be able to refer to, just in case something like this happenned. I went though all of them to ensure that I didn't miss something or install something improperly. Everything looks as it should. The correct valve body, spacer plate, and channel-plate gaskets are there, all check-balls are present and accounted for in the proper locations. Made sure I didn't mix early and late parts, etc.

I also completely disassembled, cleaned and lubed the valve body and ensured that all valves moved freely when I finished. Also tested all the solenoids. About 20K miles earlier, I had the valve-body out to replace the 1-2 & 3-4 shift valves, and to install a TCC regulator & isolator kit, TCC clutch-apply kit & modulated line boost valve kit. I never had any valve-body problems after that, but I disassembled everything again because this trans had just ground up a lot of hard parts and I didn't want to chance having any stray metal fragments causing sticky valves.

I'm trying to find somewhere local to purchase a 400psi guage so I can take some readings and not guess at what might be causing this, but in the mean time, I'm trying to gather some information and would appreciate anyone's feedback that may have had similar problems with a 4T60E, or at least just know a lot more about them than I do. I'm trying to understand what's in common between low and reverse in this particular transaxle, and at the moment, the only thing I can think of is the reverse boost valve. As I understand it, the reverse-boost valve is responsible for boosting line pressure when in low or reverse. It seems possible to me, that if it sticks, it could be causing slipping in low & reverse. I'm guessing that when I pull the vacuum hose off of the modulator, line pressure increases, and that's why the slipping stops. Almost like simulating the effect of the reverse-boost valve.

What do you folks think? I know it's hard to tell without knowing what the actual line pressure is, and that's why I'm hunting for a guage. But until I find one, I'd really appreciate your feedback as respect your expertise. I'd much rather pull the valve-body than the whole tranny again to fix it. Thanks in advance!

--mike

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Old 03-26-2007, 02:18 PM
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4t60e

the gasket set comes with two different sets of valve body gaskets, did you match those to your spacer plate? also did you check main pressure regulator valve for movement?another problem can occur on test drive the gasket between case and channel plate can blow out if you don't have the bolt's tight.two things that are used to apply forward and reverse in common,

input clutch, and input sprag

I would remove the trans look to see if input clutch shows signs of slipping check iput sprag too, I don't feel your trouble is going to be easy to find you'll need to go over everything with a fine tooth comb.
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Old 03-26-2007, 06:44 PM
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Oh, the pain........ lol

Quote:
Originally Posted by airworld2
the gasket set comes with two different sets of valve body gaskets, did you match those to your spacer plate? also did you check main pressure regulator valve for movement?another problem can occur on test drive the gasket between case and channel plate can blow out if you don't have the bolt's tight.two things that are used to apply forward and reverse in common,

input clutch, and input sprag

I would remove the trans look to see if input clutch shows signs of slipping check iput sprag too, I don't feel your trouble is going to be easy to find you'll need to go over everything with a fine tooth comb.
Hi again,

Thanks for the reply. Yep - I know about the different VB gaskets. I used the 8682280 & 8682281 for the '93. They're identical to the ones that came off. This is so annoying because I'm real meticulous about stuff like this because I only wanted to do this once. - I keep things real clean and take lots of photos to refer back to if needed.







I did check all the valves. Most were suspect, so I disassembled and cleaned everything. This thing had so much metal in it, that I went to great lengths to clean, check, lubricate, and protect everything. But still, it sure doesn't take much for a valve to stick, so I wouldn't be a bit suprised if the regulator valve, or reverse-boost valve (or both) were sticking. It's too bad really, because this VB has several Sonnax parts in it and it's worked so well for so long.

Was also very cautious about checkball locations, but still, everyone makes mistakes, so I took more pix.





As for the channel plate, I double (maybe triple) checked everything. All bolts are tight and the right gaskets are there as well. I'm pretty sure the checkballs are also in the right place too.





Interesting point about the input clutch and sprag. I hadn't considered that because it doesn't slip at all in 2nd, 3rd or 4th, and the input sprag is applied in all forward gears, right? But, then again, line pressure is (supposed to be) a lot lower, in 2, 3 & 4, because the vehicle is already moving and less force is needed to keep the clutches applied. I think that's the reason. Could be wrong. lol - I will definately check if I have to pull it.

Something else I should mention. I replaced the sprag in the 1-2 roller clutch, just because I had one. I think they use the same as the older THM-350. I seem to remember that the sprag would fit in both directions, and that surprised me. But, when I assembled it, it free-wheeled in the CCW direction and would hold in the CW direction, which is correct.



If by chance I have the sprag in upside down, and perhaps it can't hold as well as it's supposed to, can that in any way cause a slip in reverse?

Speaking of reverse, I pulled the reverse servo cover and piston out today since it's easy to get to, just to double-check the piston and pin bore, piston seal and spring. All are fine.

I really want to measure the line pressure. I couldn't find a guage locally, so I ordered one and should have it in a few days. I say that because I want to see if the line pressure jumps up when in low and/or reverse like it's supposed to. If it doesn't, then I might not have to pull the tranny again to fix it. Maybe just the side cover, pump and valve body. I'd also like to see what the pressure is in other gears as well to see if the pump has weak output. It looked fine to me, and I did replace the vanes, o-rings and seals, but anything's possible.



Well, please keep the comments and suggestions coming folks. I really, really appreciate it. I'll eventually get to the bottom of this, and when I do, I'll post the info for all. Thanks again!
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Old 03-26-2007, 09:39 PM
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nice and clean! looks better than some work of some buiders ive met.
anyways, back to the trans. it seems as though u may have cut the low/reverse piston lip seal. i say this because normally its just reverse that has the higher psi., not the forward gears... doubt if even in manual low, that ull see pressures above 125 unless u floor it. reverse should be 175-225 or higher(dont have a book in front of me).
hope thats not it, but thats what it seems like.

this is without the sprag being in the equation... maybe airworld can chime in on if thats the problem and not what i think it is...
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Old 03-26-2007, 11:30 PM
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Quote:
Originally Posted by tnsmith10
nice and clean! looks better than some work of some buiders ive met.
anyways, back to the trans. it seems as though u may have cut the low/reverse piston lip seal. i say this because normally its just reverse that has the higher psi., not the forward gears... doubt if even in manual low, that ull see pressures above 125 unless u floor it. reverse should be 175-225 or higher(dont have a book in front of me).
hope thats not it, but thats what it seems like.

this is without the sprag being in the equation... maybe airworld can chime in on if thats the problem and not what i think it is...
Hey, thanks for the compliment. I definately believe in clean when reassembling trannys.

As for the low/reverse piston lip seal.... well, to be honest.... you lost me. Low/reverse piston on a 4L60E? You sure you're not thinking of a different model trans?

To my knowledge, there are four sets of clutches (input, 2nd, 3rd, 4th), three bands (fwd, d2, reverse), and three sprags/roller clutches (input, 1-2 roller, 3rd). I'm not aware of a low/reverse piston in this particular trans. Here's a power flow chart:



As for the pressures, you're right. Reverse almost always has the higher pressure associated with it. But many trannys also boost 1st/low as well, and this is one of them. And, it varies with how much vacuum is present on the modulator. Have a look at the line-pressure chart:



I dunno. I'm hoping it's a stuck valve. I ordered a guage today and should have some readings to post in a few days. It should at least help narrow down the possibilities. I'll keep you posted. Thanks again for the reply.
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Old 03-27-2007, 06:15 AM
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4t60e

1-2 roller is correct, but as you can see it has no affect in reverse.oil pressure gauge will only waste your money,this tool stays in my tool box. your slip is deeper than oil pressure.after talking with other family member your parts supplier we have come to the conclusion I have had that problem and replaced valve body.
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Old 03-27-2007, 06:27 AM
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yea, ur right, i was just going off of what is usually in most trans... it seems like if its not a stuck valve, then possibly the sprag as u had mentioned by the chart u show...
1 thing that does come to mind by looking at the chart is, how is it in d2 or d3? does it seem to hold? if so, even with higher pressure needed for low and reverse, if it was the sprag, id imagine ud feel it in manual 2nd, or d3 as well, since the sprag is applied on both of those gears manually... gl on ur project, looks like uve done ur homework.
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Old 03-27-2007, 08:27 AM
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Quote:
Originally Posted by airworld2
1-2 roller is correct, but as you can see it has no affect in reverse.oil pressure gauge will only waste your money,this tool stays in my tool box. your slip is deeper than oil pressure.after talking with other family member your parts supplier we have come to the conclusion I have had that problem and replaced valve body.
Hi again,

I hear ya about the guage, but have one on it's way regardless. I guess I'd feel differrent if I'd spent $400-$500 for a Snap-On set, but I'm out less than $30 for guage, shipping, and hose. Just waiting for it's arrival.

I'm inclined to agree with you about the valve body. Not sure about it having to be replaced, but feel that the problem is probably related to something in the valve body. Should know within a week or so.

--mike
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Old 03-28-2007, 06:50 AM
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i did some checking in the axiom parts book yesterday and found that ur using the wrong sprag... the sprag u have is for later model, (i verified part #'s between the 350 sprag and the 1 u have in the trans now) get the right sprag...
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Old 03-28-2007, 02:09 PM
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4t60e

early 4t60e did use older 350 low roller for 1- 2 roller the didnt change until 95 or 96. you can also use early pre 87 700 low roller.
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Old 03-28-2007, 02:33 PM
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Cool - Thanks.

Quote:
Originally Posted by airworld2
early 4t60e did use older 350 low roller for 1- 2 roller the didnt change until 95 or 96. you can also use early pre 87 700 low roller.
I thought so too. Thanks for the info. Also, as you've probably already read in a different forum, I picked up another valve body this morning but don't want to tear anything apart until I measure line pressure, just to have another data point. My guage should show up today, and if it reveals what I expect (hope?) it to, I'll replace the VB rather than pulling the whole trans.

Fingers crossed......

--mike
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Old 03-28-2007, 09:02 PM
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gads, i guess its time to get glasses or my bosses axiom book is wrong... cause my axiom book agrees with u there airworld...
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Old 04-04-2007, 02:07 PM
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Input clutch - (What's wrong with this picture?) lol

Quote:
Originally Posted by airworld2
the gasket set comes with two different sets of valve body gaskets, did you match those to your spacer plate? also did you check main pressure regulator valve for movement?another problem can occur on test drive the gasket between case and channel plate can blow out if you don't have the bolt's tight.two things that are used to apply forward and reverse in common,

input clutch, and input sprag

I would remove the trans look to see if input clutch shows signs of slipping check iput sprag too, I don't feel your trouble is going to be easy to find you'll need to go over everything with a fine tooth comb.
Well, I took the pressures, and they were pretty poor (in D1 @ Rev):

D1 @ 0'' Vac - 1250 rpm ~170 psi:



Rev @ 0"" Vac - 1250 rpm ~180 psi:



D4, D3, D2 @ 18" Vac - 1250 rpm ~75 psi:



So, I ripped it apart and lookie what I found.... Bingo on the input clutch. It appears to me that no matter how careful I was, that I messed up reassembling the input/3rd drum. Have a look at the below pix. The top of the input piston is above the snap ring!

When I pulled the bottom half apart, I found the snap ring for the input clutch piston return spring assy to be out of (above) it's groove. So, I don't know if I put it in the o-ring groove instead of it's own groove, or just didn't have it seated in it's own groove, or what. Also should a thin snap-ring be where the one in the picture is? Did I reverse the thick and thin snap-rings in this drum? doh!





The pump looks fine, so I'm guessing that with the input piston being up so high that a lot of pressure was being exhausted past the lip seal, and perhaps that's why reverse was slipping as well. Just a guess though. What do you folks think? The valve body looks fine, but I already have a replacement so I'm not fooling with the old one. Live and learn I guess....

.... feeling more and more like a dummy everyday. Guess it's good that I changed careers! lol
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Old 04-04-2007, 02:35 PM
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4t60e

some sort of mis assemble on drum stack up or lip seal cut, but oil pressure low will also cause as you know burnt clutch lining.
you didn't mix up 3rd snap ring and input snap ring, its looks as if piston is bound up and not releasing the piston?
thin snap ring is for third thick is input I tried to inter change them on a drum here after you I looked at your pictures to see what it looked like it fits but doesn't look correct I guess you could make that mistake if you are not familiar with 440 or 4t60e and 4t65e drums,
thats a mistake I haven't made yet
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Old 04-10-2007, 02:11 PM
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Re-assembly... "take 3"...

Quote:
Originally Posted by airworld2
some sort of mis assemble on drum stack up or lip seal cut, but oil pressure low will also cause as you know burnt clutch lining.
you didn't mix up 3rd snap ring and input snap ring, its looks as if piston is bound up and not releasing the piston?
thin snap ring is for third thick is input I tried to inter change them on a drum here after you I looked at your pictures to see what it looked like it fits but doesn't look correct I guess you could make that mistake if you are not familiar with 440 or 4t60e and 4t65e drums,
thats a mistake I haven't made yet
Well, after going through this thing with a fine-tooth comb, I found three distinct blunders, including the input/3rd drum. I'm actually surprised it moved at all. Good thing I don't do this for a living anymore - lol

In the input drum, I definately had the snap-rings reversed. If you use the thick one in the middle of the drum for the 3rd clutches, the top of the input piston hits the snap ring and the piston won't always release. Looks like that's the whole reason for the thinner one. There's lots more space now:



You were right about having the input clutch pack too tight. Now I've got about .084 on the input clutches and about .050 on the 3rd clutches:



As for second gear (which, oddly enough was working fine) I found too much clearance there as well. Just over .095. I had Alto frictions and steels, and not enough of them. There's about .035 now:





Even 4th was toast when I tore it down. Again there was too much clearance. I found that I had a pair of .077 steels where there should have been 2 .134s' and an .077. It now has the right stuff and I've got about .050 clearance:



I should have this thing back together this evening, and hopefully for the last time. I'll let everyone know how it goes. Oh and, forget about all that nonsense I said earlier about being extremely careful when I put it together the last time. Aparently I don't know what the heck I'm doing! LOL

.......crawling back into my cave with tail between legs....
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