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Nature: "Transmission shifts satisfactorily through 2nd and 3rd speeds (Dr range), but will not shift into 4th speed (Dr range)." Cause: " Sticking 3-4 shifter valve and/or governor valves." Correction: "Completely disassemble and inspect valve body and governor assemblies".
Sounds like you spent a lot of time of the 3-4 shifter valve. Have you completely disassembled the governor assembly and inspected cleaned it?
Nature: "Transmission shifts satisfactorily through 2nd and 3rd speeds (Dr range), but will not shift into 4th speed (Dr range)." Cause: " Sticking 3-4 shifter valve and/or governor valves." Correction: "Completely disassemble and inspect valve body and governor assemblies".
Sounds like you spent a lot of time of the 3-4 shifter valve. Have you completely disassembled the governor assembly and inspected cleaned it?
I get that part, but it says governor assembly’s like plural, is there more than one? The only one I’ve seen is the one that sticks out where the side pan goes. That’s where I’m lost
I get that part, but it says governor assembly’s like plural, is there more than one? The only one I’ve seen is the one that sticks out where the side pan goes. That’s where I’m lost
and no I have not removed the governor because it sounds like there’s 2 and I’m not sure which one to remove
and no I have not removed the governor because it sounds like there’s 2 and I’m not sure which one to remove
There are at least two, but they're both in the same valve body.
See the illustration below.
The thing about these spool valves, is that they fit in their bores to very close tolerances.
At least ten thousands of an inch and maybe up to 100 thousandth tolerance.
Debris so small you can't see it can still cause problems.
check the paragraph below.
Quote; " It can be assumed that the valves and plugs are free in their operating positions.
If they will fall of their own weight in their respective bores when the valve body is shaken slightly."
There are at least two, but they're both in the same valve body.
See the illustration below.
The thing about these spool valves, is that they fit in their bores to very close tolerances.
At least ten thousands of an inch and maybe up to 100 thousandth tolerance.
Debris so small you can't see it can still cause problems.
check the paragraph below.
Quote; " It can be assumed that the valves and plugs are free in their operating positions.
If they will fall of their own weight in their respective bores when the valve body is shaken slightly."
when I cleaned the valve body I made sure all pieces were cleaned and slid back in there place with no restrictions. What about this governor that’s behind the parking bracket? Is that messing up my 4th gear? Do I need to clean it? And that rear servo I think it’s attached to the case and the bands.
when I cleaned the valve body I made sure all pieces were cleaned and slid back in there place with no restrictions. What about this governor that’s behind the parking bracket? Is that messing up my 4th gear? Do I need to clean it? And that rear servo I think it’s attached to the case and the bands.
Look at the previous illustration.
Note that parts #27, 41 & 42 comprise the 3 to 4 shift valve.
Th entire valve assembly has to come out to be cleaned.
As others have mentioned, ultrasonic cleaning is best.
Look at the previous illustration.
Note that parts #27, 41 & 42 comprise the 3 to 4 shift valve.
Th entire valve assembly has to come out to be cleaned.
As others have mentioned, ultrasonic cleaning is best.
I cleaned all those parts. I’ll do it again I guess, but there has to be another part of the trans that also controls this 3-4 shift and if I’m opening it to clean the valve body again might as well do what else controls that shift I just need to know what exactly. Governor behind parking bracket or the servos front and or rear?
I cleaned all those parts. I’ll do it again I guess, but there has to be another part of the trans that also controls this 3-4 shift and if I’m opening it to clean the valve body again might as well do what else controls that shift I just need to know what exactly. Governor behind parking bracket or the servos front and or rear?
remember that little o ring I showed you that fell out? Which by one on that illustration is that?
Look at the previous illustration.
Note that parts #27, 41 & 42 comprise the 3 to 4 shift valve.
Th entire valve assembly has to come out to be cleaned.
As others have mentioned, ultrasonic cleaning is best.
is the 3-4 shifter valve the one that has a pin holding part of it into the valve body? I want to make sure I clean whatever needs to be cleaned because last time sucked and I’m not looking forward to doing it again
im just trying figure out how it came off when the pan came off? It must go on the outside of that shifter selector. But does it go over that little pin or under it. Just doesn’t make sense how it could fall off when I took the side pan off. If anyone else has an idea of what other part I must take off and clean next time I try this operation, please jump in. And I even been watching the videos of the hydramatic rebuild on YouTube which I think that guy has commented on this post his username looks familiar. But I didn’t hear him say a lot of explanation on what each parts do.
I cleaned all those parts. I’ll do it again I guess, but there has to be another part of the trans that also controls this 3-4 shift and if I’m opening it to clean the valve body again might as well do what else controls that shift I just need to know what exactly. Governor behind parking bracket or the servos front and or rear?
The early Hydra-Matics were hydromechanically controlled.
A basic knowledge of hydraulics is helpful.
The front and rear servos apply the bands. The fact that you're getting 3 gears rules them out as a problem.
Yes, the " governor behind the parking bracket " is another valve body and should be entirely disassembled and cleaned thoroughly.
"Decisions " on when to change gears are driven by the pressure on certain valves. The pressure is created by the front and rear pumps.
It is modulated by the TV control and the gear selector (NDSLR)
Make sure all those governor valves slide freely, especially the 3 to 4 valve , # 41 on the illustration.
Last edited by Charlie Jones; Feb 26, 2024 at 09:14 AM.
The early Hydra-Matics were hydromechanically controlled.
A basic knowledge of hydraulics is helpful.
The front and rear servos apply the bands. The fact that you're getting 3 gears rules them out as a problem.
Yes, the " governor behind the parking bracket " is another valve body and should be entirely disassembled and cleaned thoroughly.
"Decisions " on when to change gears are driven by the pressure on certain valves. The pressure is created by the front and rear pumps.
It is modulated by the TV control and the gear selector (NDSLR)
Make sure all those governor valves slide freely, especially the 3 to 4 valve , # 41 on the illustration.
ok this helpful! It’s hard for me to understand things but when you dumb it down for me it helps me understand it then gives me a better chance of doing what needs to be done. Ok so I’ve done the 30mph test shut the engine off put it back in drive and the engine started up so I was told that means my pumps are good. Ok so to break it down, I will again disassemble the valve body and clean it as well as that governor behind the parking bracket. For that governor, am I just taking off what I can get to since the trans is still in the car? I know there’s two front bolts and there’s the shaft that has metal rings around it kind of like rings on the pistons in the engine. But does that come out too?
The attached diagrams might help clarify what is going on between 3rd speed and 4th speed. Basically, the rear unit doesn't change state (clutch is on in 3rd and stays on in 4th). The front unit changes by applying the clutch and taking the band off, so both clutches are applied and both bands are off.
From the diagrams, the things that can stop the front unit from going from band on/clutch off, to band off/clutch on are:
The early Hydra-Matics were hydromechanically controlled.
A basic knowledge of hydraulics is helpful.
The front and rear servos apply the bands. The fact that you're getting 3 gears rules them out as a problem.
Yes, the " governor behind the parking bracket " is another valve body and should be entirely disassembled and cleaned thoroughly.
"Decisions " on when to change gears are driven by the pressure on certain valves. The pressure is created by the front and rear pumps.
It is modulated by the TV control and the gear selector (NDSLR)
Make sure all those governor valves slide freely, especially the 3 to 4 valve , # 41 on the illustration.
just to confirm, I’m removing this governor correct?
And do I need any special tools to install it back in?
The attached diagrams might help clarify what is going on between 3rd speed and 4th speed. Basically, the rear unit doesn't change state (clutch is on in 3rd and stays on in 4th). The front unit changes by applying the clutch and taking the band off, so both clutches are applied and both bands are off.
From the diagrams, the things that can stop the front unit from going from band on/clutch off, to band off/clutch on are:
Hey guys so my super 88 55 automatic I let sit for 6 weeks after cleaning the valve body and still no 4th gear, but yesterday I finally drove it and it tried to go into 4th gear. Any ideas?
The most likely candidate to resolve your issue is going to be a new transmission since it's likely the rear transmission band has broken. Simply pointing out the basic truth straight-away up front.
NOTE: In the URL link I sent to you what Glenn (redoldsman) states:
If you can find a 55 transmission fine, if you can find a 54 transmission even better.
I thought if it was going into third then it wasn’t the rear band? Again just cleaned and inspected the whole valve body and let it cook in one of those high temp cleaners and put it back together using atf on each part and still no 4th gear so idk now
Chris,
When you get brave enough to tackle tearing down the valve, I would suggest you invest in an Ultra Sonic Cleaner. You can get a small one at Harbor Freight for about $90. It's the only way to go when you want to get small parts clean. All you need is warm water and a shot glass of Simple Green. The parts will come out looking like new. Just make sure you take lots of pictures as you take the valve apart. The diagrams in the manual are very detailed but you need to make sure you identify each spring and each valve spool as you take the valve apart.
I've done a couple valves so if you need help just let me know.
Wally
so I’ve cleaned the valve body a second time with ultrasonicccleaner. Can someone explain what goes on in the trans when it goes from 3 to 4th gear?? It can’t all be only valve body. Is part of it the rear band? Rear servo? Governor where parking pawl is? I’m wondering if my rear band needs adjusted?
Chris - Post #94 specifically states what happens with the transmission when the shift is from 3rd to 4th gear. I've include the .pdf file as an attachment.
Chris - Post #94 specifically states what happens with the transmission when the shift is from 3rd to 4th gear. I've include the .pdf file as an attachment.
so it could be the front band not releasing or could be the pressure regulator? Cuz my VB is spotless as should be. I know it’s all been stated before I’m just having a hard time understand it.
The attached diagrams might help clarify what is going on between 3rd speed and 4th speed. Basically, the rear unit doesn't change state (clutch is on in 3rd and stays on in 4th). The front unit changes by applying the clutch and taking the band off, so both clutches are applied and both bands are off.
From the diagrams, the things that can stop the front unit from going from band on/clutch off, to band off/clutch on are:
I didnt have time to read all 100+ responses. Pardon if this was discussed/performed.
Did you check the trans pressures in each gear? That's the first step in troubleshooting a hydraulic pump. (aka a trans). A cross leak will be blatantly evident.
I didnt have time to read all 100+ responses. Pardon if this was discussed/performed.
Did you check the trans pressures in each gear? That's the first step in troubleshooting a hydraulic pump. (aka a trans). A cross leak will be blatantly evident.
I did do the pump test driving at 35mph and shut the car off and put it in drive came right back on, is that what you mean by pressure test?
I did do the pump test driving at 35mph and shut the car off and put it in drive came right back on, is that what you mean by pressure test?
also, I noticed a nut right above the side pan which adjust one of the bands, would that need adjusting if I’m getting up to third gear? Maybe it’s not releasing to get into 4th?
Should be a pressure port somewhere on that trans. I know nothing about that model.
A hydraulic trans is a hydraulic trans. They mostly operate off the same hydraulic principals, thus similar troubleshooting techniques.
Part of trans troubleshooting is reading the pressures in each gear, while its on the lift. There are specific pressure ranges to look at. Get a hydraulic pressure gauge that goes to 300PSI or more. Plug it into the service port and read away. You will need find those specs. I don't have GM Hydramatic books. I have Hydra-Matic books 1965 and up.
Pressures above or below the recommended ranges indicates a cross leak in a hydraulic circuit or a blockage. Narrow it down to which circuits bad then rip into it and look for the defect. Blown lip seal bad frictions broken springs or other hard parts. Which means time for a rebuild.
A band adjustment isn't going to help with no 4th gear. Liken a band adjustment to adjusting shoe brakes. It just improves hold operation on the drum.
I wasn't aware of any 4 forward gear automatics in any GM until the 200 & 700 series GM transmissions in the 80s...until I just Googled it. Never done learning. Makes one wonder why GM didn't keep building 4 speed autos between 55 and mid 80s. Cheap gas?
Last edited by droldsmorland; May 16, 2024 at 05:54 PM.
Should be a pressure port somewhere on that trans. I know nothing about that model.
A hydraulic trans is a hydraulic trans. They mostly operate off the same hydraulic principals, thus similar troubleshooting techniques.
Part of trans troubleshooting is reading the pressures in each gear, while its on the lift. There are specific pressure ranges to look at. Get a hydraulic pressure gauge that goes to 300PSI or more. Plug it into the service port and read away. You will need find those specs. I don't have GM Hydramatic books. I have Hydra-Matic books 1965 and up.
Pressures above or below the recommended ranges indicates a cross leak in a hydraulic circuit or a blockage. Narrow it down to which circuits bad then rip into it and look for the defect. Blown lip seal bad frictions broken springs or other hard parts. Which means time for a rebuild.
A band adjustment isn't going to help with no 4th gear. Liken a band adjustment to adjusting shoe brakes. It just improves hold operation on the drum.
I wasn't aware of any 4 forward gear automatics in any GM until the 200 & 700 series GM transmissions in the 80s...until I just Googled it. Never done learning. Makes one wonder why GM didn't keep building 4 speed autos between 55 and mid 80s. Cheap gas?
I saw the opening where a pressure gauge would hook up but is that really necessary if I’m get 1-3 gears and not fourth. Obviously some kind of pressure is there. I’m wondering where the double transition valve is in the trans and if I can get to it? As I’ve asked before, is there a governor not in the valve body that needs my attention? I’m for sure checking out that pressure regulator valve this weekend. I’m just trying to find all things I can do besides the valve body since I already did that, that I can get to while the trans is still in the car and I don’t have a lift. So I gotta do the best with what I got. Any volunteers want guide me thru some steps on Saturday send me a private message with your number because this messages back and forth takes too long and can be undetailed enough some times
Any other advice guys I’m gonna tackle this tomorrow. I’ve been reading the book and watching videos but it’s a lot of information and I’m only concerned with getting into 4th gear and what causes that. Pretty sure in the valve body the 3-4 shifter valve has a pin that goes in to hold it in place but I don’t see in the book how exactly that works. I just put it back in the way it looked like it was.
Should be a pressure port somewhere on that trans. I know nothing about that model.
A hydraulic trans is a hydraulic trans. They mostly operate off the same hydraulic principals, thus similar troubleshooting techniques.
Part of trans troubleshooting is reading the pressures in each gear, while its on the lift. There are specific pressure ranges to look at. Get a hydraulic pressure gauge that goes to 300PSI or more. Plug it into the service port and read away. You will need find those specs. I don't have GM Hydramatic books. I have Hydra-Matic books 1965 and up.
Pressures above or below the recommended ranges indicates a cross leak in a hydraulic circuit or a blockage. Narrow it down to which circuits bad then rip into it and look for the defect. Blown lip seal bad frictions broken springs or other hard parts. Which means time for a rebuild.
A band adjustment isn't going to help with no 4th gear. Liken a band adjustment to adjusting shoe brakes. It just improves hold operation on the drum.
I wasn't aware of any 4 forward gear automatics in any GM until the 200 & 700 series GM transmissions in the 80s...until I just Googled it. Never done learning. Makes one wonder why GM didn't keep building 4 speed autos between 55 and mid 80s. Cheap gas?
if there’s no 4th gear is there a band that is applying or not applying and if so which band would that be?
There are no bands applied in 4th gear. Only clutches.
Here is a troubleshooting chart courtesy of Motor's Auto Repair Manual.
yhank you for the images, I pulled out the 3-4 shifter valve and governor with parking pawl and cleaned up everything however now my car won’t go into any gear! If I put it in a gear and rec it high it will jerk the car and kill it like it’s Ben trying to go so I have no clue now
It sounds like you've given it your best and it might be time to bite the bullet and pull it out and do a full rebuild. It's pretty difficult to try what you're doing laying on the ground outside in your driveway. Even seasoned mechanics wouldn't attempt a transmission, that's why there are people who specialize in transmissions and there are very few in the whole country who want to do one of these.
It sounds like you've given it your best and it might be time to bite the bullet and pull it out and do a full rebuild. It's pretty difficult to try what you're doing laying on the ground outside in your driveway. Even seasoned mechanics wouldn't attempt a transmission, that's why there are people who specialize in transmissions and there are very few in the whole country who want to do one of these.
I watch ed the hydramatic rebuild part 1-3 but he doesn’t say what parts do what. My problem is that it used to go 1-3 years no doesn’t even go into gear so I’m puzzled
Try watching these if you really want to learn about it and are willing to try the rebuild yourself.
This first one it's a five part series given by a professor from a tech college.
In this second one he does a full tear down and rebuild. https://www.youtube.com/@johndodd6150
In this third one he does a rebuild and does a really good job of detailing the assembly and gives information on what other books to source and tools. It's a three part series but everything has already been apart and cleaned.
