700r4 output seal

[good times]

Just wondering if i can replace the output shaft seal on my 700r4 wirhout pulling the tranny and if there are any special tools i will need for this.

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[chengny]

FWIW:

I had a problem that I thought was a rear tranny seal leaking. I probably changed the seal three times, and it still leaked. I had the truck up on jack stands working on the exhaust for a few days with the front of the truck higher than the rear. This thing was leaking pretty bad. Enough to cause a puddle on the floor. Then I found the answer to my problem. This is a very easy fix to an annoying problem. I never knew this existed. Learn something new everyday I guess.

Some GM transmission yokes, primarily those used on trucks, have a weep hole that relieves pressure buildup caused by the yoke moving back an forth as the vehicle passes over bumps and other road irregularities. If the trans in your truck leaks fluid when the vehicle is parked uphill, fluid may be coming out of the weep hole due to failure of an output shaft O-ring.

If your truck has this weep hole (arrow in photo below), you will be able to see it with the driveshaft removed by flipping the yoke to the side. It will be in the center behind the u-joint.

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The O-ring in question (pn GM3764601, 700R4 shown) is installed in the cup on the transmission output shaft (arrow in photo below). Access it by removing the transmission extension housing.

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To remove the extension housing, you will need to remove the driveshaft. Be prepared to catch any tranny fluid that comes out. Mark the location of the rear u-joint on the pinion yoke at the rear so you can install it in the same location. This will make sure it is not installed out of balance. You will need to pry the u-joint out of the rear yoke a little. Be careful to not let the cups fall off the u-joint. Next remove the speedo cable from the sleeve in the extension housing. Now unbolt the extension housing from the transmission. Again catch the transmission fluid. Make sure the rubber seal on the extension housing is intact. You should see something similar to the above photo depending on what type of transmission you have. Make a mental note of where the metal cup is located at on the output shaft and slide the cup off. The O-ring, (pn GM3764601) will be in the groove inside the cup. Replace the O-ring and slide the cup back on the shaft. Try to get the output shaft in the center of the cup as best you can. This will let the driveshaft yoke go all the way in without it hitting the end of the cup. The rest is the reverse of removal. To help from ruining another O-ring, use a little tranny fluid on the outside of the yoke before sliding it back into the transmission. This will also help save the rear seal from damage.

 

[350runner]

Hey Jerry do you by chance have a link that sells these o rings. I know for sure I need one.

Sent from the dust in front of you!

 

[350runner]

Found one. http://www.makcotransmissionparts.com/64380.html

Sent from the dust in front of you!

 

[chengny]

Good - I am going to start charging these vendors a sales commision for all the business I shoot them.

 

[350runner]

You must be registered for see images attach

Sent from the dust in front of you!

 

[MadOgre]

FWIW:

I had a problem that I thought was a rear tranny seal leaking. I probably changed the seal three times, and it still leaked. I had the truck up on jack stands working on the exhaust for a few days with the front of the truck higher than the rear. This thing was leaking pretty bad. Enough to cause a puddle on the floor. Then I found the answer to my problem. This is a very easy fix to an annoying problem. I never knew this existed. Learn something new everyday I guess.

Some GM transmission yokes, primarily those used on trucks, have a weep hole that relieves pressure buildup caused by the yoke moving back an forth as the vehicle passes over bumps and other road irregularities. If the trans in your truck leaks fluid when the vehicle is parked uphill, fluid may be coming out of the weep hole due to failure of an output shaft O-ring.

If your truck has this weep hole (arrow in photo below), you will be able to see it with the driveshaft removed by flipping the yoke to the side. It will be in the center behind the u-joint.

You must be registered for see images attach

The O-ring in question (pn GM3764601, 700R4 shown) is installed in the cup on the transmission output shaft (arrow in photo below). Access it by removing the transmission extension housing.

You must be registered for see images attach

To remove the extension housing, you will need to remove the driveshaft. Be prepared to catch any tranny fluid that comes out. Mark the location of the rear u-joint on the pinion yoke at the rear so you can install it in the same location. This will make sure it is not installed out of balance. You will need to pry the u-joint out of the rear yoke a little. Be careful to not let the cups fall off the u-joint. Next remove the speedo cable from the sleeve in the extension housing. Now unbolt the extension housing from the transmission. Again catch the transmission fluid. Make sure the rubber seal on the extension housing is intact. You should see something similar to the above photo depending on what type of transmission you have. Make a mental note of where the metal cup is located at on the output shaft and slide the cup off. The O-ring, (pn GM3764601) will be in the groove inside the cup. Replace the O-ring and slide the cup back on the shaft. Try to get the output shaft in the center of the cup as best you can. This will let the driveshaft yoke go all the way in without it hitting the end of the cup. The rest is the reverse of removal. To help from ruining another O-ring, use a little tranny fluid on the outside of the yoke before sliding it back into the transmission. This will also help save the rear seal from damage.

That would not apply to a 4wd

 

[MadOgre]

On the rear of the transfer case with the drive shaft removed use a screw driver and hammer to punch the metal outer part of the seal in towards the out put shaft. You may have to do this in several places on the seal then simply pull it out. Be sure not to damage the tail housing or out put shaft.

If there is a weep hole in your yoke installed on your transfer case I would suggest buying one that does not have that or plug it with some thing like a set screw or grease nipple, although be sure to never pump grease into it LOL.

The transfer case pumps fluid down the inside of the out put shaft to the end and then is forced through the mating splines of the yoke and out put shaft and returns to the transfer case through the rear bearing.

If you have a 4wd and there is a hole in your yoke you have a problem.

 

[chengny]

Hence the "FWIW" preface.

I didn't know if he was talking about the case extension seal or the output shaft seal. I first thought case extension , so here is what I first responded with:

Rear Oil Seal Replace

1.Remove drive shaft.
2.Pry out seal with screwdriver.
3.Install new seal with a suitable seal driver.
4.Install drive shaft.

But when I read it, I thought it came across as kind of sarcastic. So I deleted that and thought I would discuss the most likely reason for his leak (a worn output shaft seal/o-ring). The weep hole aspect was included as a bonus.

A TSB on this issue:

File In Section: 4 - Drive Axle

Bulletin No.: 46-41-01

Date: September, 1994

INFORMATION

Subject:
Slip Yoke Replacement and U-Joint Servicing

Models:
1995 and Prior Light Duty Trucks

U-joints that are pressed out of the propeller shaft or slip yoke must not be re-used. When it is necessary to press out the u-joint to replace a slip yoke, a new u-joint must be installed. A new u-joint is necessary as the bearing cup seals and slingers are easily damaged. If these components are damaged, dirt and water can contaminate the bearing causing early bearing wear-out. Replacement of the rear u-joint is not required if the retaining straps holding the u-joint to the rear axle pinion flange are removed.

Light duty trucks make use of three types of yokes:

1. Vented slip yoke. This yoke can be identified by a small hole in the center of the slip yoke welch plug. This yoke uses grease for internal lubrication. The internal splines of the yoke should be coated with a light covering of grease before installation to the output shaft. A small amount of grease may be forced from the vent hole during operation. No attempts should be made to plug the vent hole.

2. Non-vented slip yoke. This yoke has no vent hole and relies on transmission or transfer case fluid for internal lubrication. Grease should not be used on the yoke internal splines as it may contaminate the transmission or transfer case fluid.

3. Bolted or fixed yoke. This yoke does not slide so it needs no internal lubrication.


The transmission/transfer case output shaft seal should be inspected for damage before installing the yoke. The seal lips should also be greased before yoke installation for longer seal life and better performance.

 

[chengny]

Here are a couple of images. They probably won't be much help, but they at least show what the parts look like and how easy the job would be if you had those special tools:

You must be registered for see images attach

You must be registered for see images attach

 

[350runner]

Thanks man!

Sent from the dust in front of you!

 

[MadOgre]

Hence the "FWIW" preface.

I didn't know if he was talking about the case extension seal or the output shaft seal. I first thought case extension , so here is what I first responded with:

Rear Oil Seal Replace

1.Remove drive shaft.
2.Pry out seal with screwdriver.
3.Install new seal with a suitable seal driver.
4.Install drive shaft.

But when I read it, I thought it came across as kind of sarcastic. So I deleted that and thought I would discuss the most likely reason for his leak (a worn output shaft seal/o-ring). The weep hole aspect was included as a bonus.

A TSB on this issue:

File In Section: 4 - Drive Axle

Bulletin No.: 46-41-01

Date: September, 1994

INFORMATION

Subject:
Slip Yoke Replacement and U-Joint Servicing

Models:
1995 and Prior Light Duty Trucks

U-joints that are pressed out of the propeller shaft or slip yoke must not be re-used. When it is necessary to press out the u-joint to replace a slip yoke, a new u-joint must be installed. A new u-joint is necessary as the bearing cup seals and slingers are easily damaged. If these components are damaged, dirt and water can contaminate the bearing causing early bearing wear-out. Replacement of the rear u-joint is not required if the retaining straps holding the u-joint to the rear axle pinion flange are removed.

Light duty trucks make use of three types of yokes:

1. Vented slip yoke. This yoke can be identified by a small hole in the center of the slip yoke welch plug. This yoke uses grease for internal lubrication. The internal splines of the yoke should be coated with a light covering of grease before installation to the output shaft. A small amount of grease may be forced from the vent hole during operation. No attempts should be made to plug the vent hole.

2. Non-vented slip yoke. This yoke has no vent hole and relies on transmission or transfer case fluid for internal lubrication. Grease should not be used on the yoke internal splines as it may contaminate the transmission or transfer case fluid.

3. Bolted or fixed yoke. This yoke does not slide so it needs no internal lubrication.


The transmission/transfer case output shaft seal should be inspected for damage before installing the yoke. The seal lips should also be greased before yoke installation for longer seal life and better performance.

lol sorry I seriously don't know what FWIW stands for.

 

[350runner]

For what it's worth...

Sent from the dust in front of you!

 

[chengny]

You know that Buffalo Springfield song that starts with "Stop children, what's that sound?". The name of that song is "For What It's Worth".

 

[oneluckypops]

Everything above is really good advise. But unless I missed it no one really touched on a couple different things.

A properly lubricated seal does not go bad for no reason, worn out bushings and or bearings cause them to fail. Be sure to check for excessive slop in the output shaft, very common for rear case bushings to fail and cause the seal to fail.

Also on the weep hole leaks in the pinion shafts, If you develop a leak in this area I highly suggest you check for a plugged transmission case vent tube. If you have a plugged up vent tube and you plug your weep hole in the pinion you can have several future problems arise
High case pressure causing fluid to blow the dipstick out of the tube and loose fluid there, older weaker valve body gaskets can blow out, as well as input shaft seals.