Transmission is out and pump lugs are good. T/V has movement as well. RVMB built by Tubro Action.
727 Help Please
- Thread starter Illahe
- Start date
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Hmm. Did you take the pump all the way apart or just look in the reaction shaft support and see the lugs?
The pump is apart and appears to be all right, though I did take some of the stator support off on the lathe to remove the groves in the face. Going re-assemble the pump to check the end play of the transmission. Air check the servos, and the clutch packs. Don’t know how to inspect the V/B.
Next question, can you post a picture of your input shaft, and stator support to make sure the years match up?
If just the front pump is removed from the transmission, you will be able to see if the input shaft broke free from the input hub. I doubt that happened, but a good visual check to ensure. Going to a neutral box is not very common. At least not in my experience.
You installed the valve body out of the box from turbo action correct? What is the part number in the valve body? Is it 17156?
I’ll check and see if it’s got a # engraved.
The stater support and input have the two ceiling rings. I believe it’s the 71 through 75. I did have to take some material off the stater support face that’s up against the pump gear. It was scored up a little bit. I had a local guy spin on the lathe and take the Scores out of it. When I spoke to the local transmission shop, they suggested I reassemble and check the input shaft play.
Did you take the front pump and stator support apart or did you just remove the front pump from the trans and leave it as a whole unit? Please post photos of the stator support and pump body separated with the pump gears in the body still. ***I apologize you already said you took it all the way apart. I am getting up for work and forgot you responded to that question lol.
.062 is a little much end play for a race unit. But I wouldn’t expect it to become a neutral box from having that much end play with only a few minutes of run time.
The valve body is a simple turbo action reverse manual non low band apply with only one check ball inside.
I am a little stumped on this one. I would probably be taking the trans fully apart and re checking everything. If you lost pressure, you will see that in the clutches if you ran it for a while while it would not move forward or backward.
I would be making sure the converter is not damaged and that’s the issue. The turbine is what drives the input shaft but needs fluid pressure to do so. So like I said I’m a little stumped with the front pump lugs being in tact.
.062 is a little much end play for a race unit. But I wouldn’t expect it to become a neutral box from having that much end play with only a few minutes of run time.
The valve body is a simple turbo action reverse manual non low band apply with only one check ball inside.
I am a little stumped on this one. I would probably be taking the trans fully apart and re checking everything. If you lost pressure, you will see that in the clutches if you ran it for a while while it would not move forward or backward.
I would be making sure the converter is not damaged and that’s the issue. The turbine is what drives the input shaft but needs fluid pressure to do so. So like I said I’m a little stumped with the front pump lugs being in tact.
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Is there 2 sealing rings on the pump stator? Kim
I was thinking same thing Kim looking at the photo. but was trying to figure out how that would still not allow the car to go forward in 1st gear or 2nd gear.
There still may be more than 1 problem. Then with the pump gears being milled down could they be causing cavitation? Maybe he has the lu input shaft in a regular converter. I don’t know if that would even fit. Pics sure would help.
OP R U GONNA POST ANY PICS?
Ya I was kind of wondering if there was more than one thing going on as well. Sure seems pump related as I know you agree.
Yes, there are two sealing rings on the pump stator. I just air checked the unit as I did on the build and the servo's apply along with the clutch packs when pressurized. Then verified the pump clearances and they are .0035 with a depth mic and and the paper to housing clearance test is good.
When Installed, I filled the torque converter and the trans mission. I did light it off in park until the engine was timed and idle set as its a solid flat tappet build. The fluid was foaming so the unit was cycled to neutral and topped off again.
There are pics in the thread. I have the pump down and will post a few pics in 5 minutes.
Foaming fluid certainly points to cavitation. Did it continue to foam after putting it in neutral? I think Kim is onto something with the milling of the pump stator support. Pump gears being .0035 down may be an issue. But I don’t have the specs in front of me of what is considered acceptable on this measurement to be certain.
No, the trans fluid settled down when it was cycled into neutral. after the unit lost power transmission the transmission was over full. When the unit was pulled the converter had hardly any fluid in it.
With the fluid being over full while the car was running, after you lost movement, that tells me you lost pressure and fluid was no longer being pushed through the transmission. Whether it be from the front pump, the converter, or an internal part in the transmission failed causing no movement. Something quit functioning properly.
You’re to the point where I would completely disassemble the transmission, inspect every component with a fine tooth comb, and if all checks out, re assemble. If everything checks out, I would get the converter swapped out, even if you have a loaner, just to see if that fixes the issue.
If the stator in the converter fails, which is the fluid coupling device in the converter that multiplies the torque, I believe you would lose movement. Especially after doing a stall speed test, which is hard on stators.
I am to the point of spit balling because if someone came to me with this problem and the transmission checked out, I would be looking at the converter as the failure point.
Kim, thoughts?
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Thank you! Its a brand new converter. 8" 4700 stall, mechanical diode. The converter function, though, is beyond my understanding. Thank you for the help.
Well the mechanical diode is much stronger than a conventional sprag, but there are other components in a converter which could fail. What brand converter is it?
Also do you have access to another front pump?
Dynamic brand Converter. I have several cores here that could be pillaged for a pump.
I would get a front pump out of one of your cores. Making sure it’s 1971-1977 stator.
Take it apart, clean it, re assemble it. Then use that in your transmission. I would also tighten up the end play to .020-.030 assuming you have thrust washers in your geartrain and not Torrington bearings.
I am by no means someone who claims to know it all, because I do not. There may be others who disagree, which is fine, but if it were a transmission that I was building for someone who is experiencing the same issues you are, that is how I would approach the situation.
Thank you, Sir.
Those pump gears look pretty bad in my poinion. Is this after they were cleaned up? It could possibly be the converter valve in the valve body is in backwards or the manual valve is misadjusted. With next to no atf in the converter it sure sounds like the pump. Kim
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