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Rob

Leaking Range Valve:

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Posted (edited)

Been chasing an air leak under my 80 R-612 and have traced it to the transmission range valve leaking out the vent. It is an A-4688 style valve. My spare transmission has an A-5000 mounted on it and I'm going to order a replacement valve for the R model. Is the A-5000 a better valve or should I stay with the A-4688 as both are readily available and about the same cost.

Thanks,

 

Edited by Rob

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Posted (edited)

Pretty easy decision. The A-4688 valve is cast iron construction and the A-5000 is cast aluminum. Obviously a cost saving measure to Eaton.

A rebuild kit for either valve is right at $9.00 so I'll rebuild both the original, and a spare I found on the shelf. I actually have an A-4688 on my storage shelf and after taking it apart is very simple. The rebuilt kit consists of O rings, seals, and compression springs with a perimeter gasket where the block seals to the transmission case.

With a piece of fuel line hose taped to a yard stick for reach, and the other end of the hose to my ear, I can plainly hear the rush of air through the exhaust vent. This is whether the range is in high or low, overdrive, or direct so the leak is through the sealing ring on the inlet side of the sliding piston, (#23 in the A-4688 diagram).

 

 

 

Edited by Rob

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3 hours ago, Rob said:

Been chasing an air leak under my 80 R-612 and have traced it to the transmission range valve leaking out the vent. It is an A-4688 style valve. My spare transmission has an A-5000 mounted on it and I'm going to order a replacement valve for the R model. Is the A-5000 a better valve or should I stay with the A-4688 as both are readily available and about the same cost.

Thanks,

image.png.e2790609abef7fc23ee932bab28ad04d.png

Not trying to be smart ass, but we usually ask you these questions.

 

1 hour ago, Rob said:

Pretty easy decision. The A-4688 valve is cast iron construction and the A-5000 is cast aluminum. Obviously a cost saving measure to Eaton.

A rebuild kit for either valve is right at $9.00 so I'll rebuild both the original, and a spare I found on the shelf. I actually have an A-4688 on my storage shelf and after taking it apart is very simple. The rebuilt kit consists of O rings, seals, and compression springs with a perimeter gasket where the block seals to the transmission case.

With a piece of fuel line hose taped to a yard stick for reach, and the other end of the hose to my ear, I can plainly hear the rush of air through the exhaust vent. This is whether the range is in high or low, overdrive, or direct so the leak is through the sealing ring on the inlet side of the sliding piston, (#23 in the A-4688 diagram).

image.png.5cf0f5f5d76bae7f03f8f9936c27c1d4.png

image.thumb.png.e3ae4d78b60c11557623f75c35126aba.png

image.png.2355bd9f366b448b886a5018b55644cf.png

See. You’ve already got it figured out.

LOL!

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We all get lucky I suppose.....

Took the pressure washer with a heavy soap concentration to soak everything to look for bubbles. Found a pressure regulator leaking for the release cylinder on the winch drum, and valve plate on the compressor cylinder head, (Midland 1300) when it was running, and that was it. The air leak would deplete the receiver(s) setting the brakes in about 20 minutes, (tops) so was a pretty good leak. I don't have the best of hearing any longer thanks to close proximity jet engines at airfields, but setting on the shop floor with my head between the transmission and frame rail I could hear air escaping. Tape measure wasn't stiff enough to hold the fuel line stable so the yard stick came into play. Worked well going under the cab but above the fuel tank to get right at the area.

Necessity is the mother of invention sometimes.

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Can’t hear nothing but a ring in my ears, 

(blame that on dumbass when younger) can’t see nothing without reading glasses on & a flashlight. Getting old is tough!

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Do it up 100% no air issues, oil or coolant drips and no grease on zerks or past seals. DOT goes over board on us that run older units. They seem to feel that we are easy marks. Paul

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I've always had that ringing since a boy. I kinda overcome it and it's always been there so natural for me. Airfields, diesel engine generators, diesel trucks, and firearms haven't done me no favors through the years as far as hearing.

"Momma" swears I have selective hearing however.

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1 minute ago, 41chevy said:

Do it up 100% no air issues, oil or coolant drips and no grease on zerks or past seals. DOT goes over board on us that run older units. They seem to feel that we are easy marks. Paul

Been heavy onto that of late. Been through several cans of "Easy-Off" oven cleaner to break years of caked on grease buildup as the truck really was no stranger to a grease gun. Throwoff areas of the universals have more than an inch of "cake" from flinging grease.

Started researching insurance this morning for lowboy type work. Going to get the truck working before going through a cleanup and new paint. Once I get the proper insurance in force it's easy to switch trucks on the policy while one is worked on. Really want to doll this one up and have the tanks and front wheels polished as it's pretty ratty looking now. I noticed I'm down to about 40% brakes on all wheel ends so going to pull a drum to measure and ensure they are legal yet too.

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The air leak at the vent can also be a seal leaking from the rear box inside or a pto air control leaking to the inside.

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9 minutes ago, theakerstwo said:

The air leak at the vent can also be a seal leaking from the rear box inside or a pto air control leaking to the inside.

Ditto. The Combination Cylinder disk cracked on my 8ll a couple years ago, resulting in a decent leak through the vent as the air would leak to the vented side of the high/lo range

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Posted (edited)

The main case vent in the top cover is not leaking. The vent leaking is the one on the A-4688 valve itself, (#23 in the attachment).

 

 

Edited by Rob

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48 minutes ago, theakerstwo said:

The air leak at the vent can also be a seal leaking from the rear box inside or a pto air control leaking to the inside.

I don't have an air shift PTO on the truck and did check both the splitter, and range cylinders with regulated shop air when bench checking the transmission prior to the install. This range valve is from the original transmission, but was not tested prior to the swap to this transmission. It was not presenting problems in the earlier installation I know of. There were however two hoses replaced at the same time citing decay, and age. Don't know if they leaked or not but were not going to last long if left in service. Can't really disconnect the lines for the range valve easily with the valve in the truck so did not.

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9 minutes ago, Rob said:

I don't have an air shift PTO on the truck and did check both the splitter, and range cylinders with regulated shop air when bench checking the transmission prior to the install. This range valve is from the original transmission, but was not tested prior to the swap to this transmission. It was not presenting problems in the earlier installation I know of. There were however two hoses replaced at the same time citing decay, and age. Don't know if they leaked or not but were not going to last long if left in service. Can't really disconnect the lines for the range valve easily with the valve in the truck so did not.

Although it doesn't matter the top cover in this truck is the set forward shift position meaning the transmission is an RTOF-12513 where the donor transmission now installed was an RTO-12513. The "F" designation relates to the top shift cover and placement of the shift handle in this cover. It is a direct bolt on swap for the two types. I have complete gasket and seal kits in my cabinet for this series of transmission but didn't need them for this swap.

Soon as I run across an 18 speed priced reasonable, this one too will come back out.

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Posted (edited)

Hopefully back in good graces:

 

 

She appears to be pleased but we'll see how long that holds out:

 

 

 

242K on the clock and we'll probably see 300K, or until it rusts to the ground. Been a good car which we purchased new.

Edited by Rob
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That's what you call getting your moneys worth, with that many miles!!    terry:MackLogo:

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New valve installed this evening and air leak is history. Ordered a new valve plate gasket for the top of the compressor but won't see it till next week. 

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Rob it may be the valve bad but it also can be air by/passing the hi/low cyl seal on the piston.A way to check that is when range is I hi range take the line off of the front port of the range cyl.If air is come from the port of the cyl then the cyl may be rusty and leaking by.

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8 minutes ago, theakerstwo said:

Rob it may be the valve bad but it also can be air by/passing the hi/low cyl seal on the piston.A way to check that is when range is I hi range take the line off of the front port of the range cyl.If air is come from the port of the cyl then the cyl may be rusty and leaking by.

Hi Glenn;

I kinda did as you suggest but pulled the lines at the range, and splitter cylinder(s) pressurizing each side with 60psi and didn't notice any leakage in these area(s). The lines are easy to remove at the cylinders. I've not mocked up a jig to test the valve itself but it looks clean through the ports. I've not taken it apart but plan to for a good look. They could, or may leak at higher pressure but I seem to remember they normally operate at about 60psi effectively?

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Posted (edited)

Left the truck with just about 120psi, (governor shut off pressure) in the receivers last night and it's about 115psi this morning. It's lost about 5psi in the overnight hours so probably going to call it good at this time. The truck has always lost it's pressure overnight but was able to hold it several hours before setting the brakes in the past. Don't get the impression I don't set the brakes, but I do test this ability often as it ensures the diaphragms are good in the emergency side of the chambers. Years ago I had one with a slight leak and the inspector let me through with a promise I'd change it. I did when back at the shop as spares are kept. 

Edited by Rob

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You know how all those "attaboys" build up and it takes a single "Aw Shit"! moment to wipe them all out? Well, I've returned to square one as I burnt her toast this morning.....

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Burnt toast and rotten must have a tape worm 

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Excessive speed blows the paint off the spoiler, she might need to slow it down a little.

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10 hours ago, other dog said:

Excessive speed blows the paint off the spoiler, she might need to slow it down a little.

I'll let you tell her that. Word to the wise would be keep your distance when you start.😉

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