Transmission Leak

[texasmike]

After my '84 C10 sits for 3-4 days, oil from the convertor drains back into the pan, raising the level and leaking out through the splines in the slip yoke. I'm trying to find a good quality replacement, such as Spicer or Dana, before removing the drive shaft. Everything is original with a 700R4 transmission.
Can anyone tell me what the center-line of joint to the end of spline measurement is and where I can find a good quality new replacement yoke? I've been told that repairs to stop the leaking usually don't work.
Thanks everyone.

 

[Bextreme04]

After my '84 C10 sits for 3-4 days, oil from the convertor drains back into the pan, raising the level and leaking out through the splines in the slip yoke. I'm trying to find a good quality replacement, such as Spicer or Dana, before removing the drive shaft. Everything is original with a 700R4 transmission.
Can anyone tell me what the center-line of joint to the end of spline measurement is and where I can find a good quality new replacement yoke? I've been told that repairs to stop the leaking usually don't work.
Thanks everyone.

Replacement what? There are two styles of slip yoke. If yours has a hole on the end under the u-joint that the fluid is leaking from, then you should have an O-ring and sleeve on the output shaft. When you start getting fluid leaking out of the slip yoke, that O-ring has usually failed.

 

[texasmike]

I didn't want to go into the transmission to replace the sleeve and O-ring and was told to find a yoke without a hole in the end of it.

 

[Bextreme04]

I didn't want to go into the transmission to replace the sleeve and O-ring and was told to find a yoke without a hole in the end of it.

I'm so confused. You would rather buy a whole new yoke, than buy a $0.58 o-ring? You still need to pull the sleeve and old o-ring off if you are going to put a different design slip yoke in there. I would personally just pull the extension housing off and replace the bushing and seal on the bench while allowing easier access to the sleeve and seal at the same time. It's 4 bolts... should take all of 5 minutes to remove.

I would order parts #348, 374, 066, and 074 in this drawing. https://www.wittrans.com/parts?type=700R4&section=52_case

If you are at the point where the inner o-ring is busted and leaking, you are likely at the point where that bushing will be worn and the output seal is also worn. All of those bushings and seals should run you less than $20 combined and are readily available almost anywhere. If you dont feel comfortable pressing in new bushings or ordering parts, just pull the extension housing and take it down to your local transmission shop. They can replace the bushing and seal and give you the tailshaft seal and extension housing o-ring right off their parts shelf usually. I would bet $60 for the local transmission shop to do it for you including cost of parts. It's literally a 5-10 minute job for them to do that.

A new yoke is going to cost you close to that or more and you will still want a new bushing and seal and have to access the sleeve and o-ring to remove them or they will interfere with the new yoke.

 

[texasmike]

Thanks for all of your time to help me with this issue, Eric. I see that I'm going to have to give this a lot more thought and planning. I am just a shade tree mechanic who is approaching 80 and don't feel very comfortable with some projects. Getting to the ground and back up can be a challenge sometime and laying on my back under the truck isn't real inviting. I don't mean to sound like a wimp or a ***** but it is what it is. My concern is F'ing something up and then trying to find help to come to my home or having the truck towed to a repair shop. Good trustworthy help is so hard to come by these days.
Thanks again.
Mike

 

[texasmike]

Eric, can you answer a few questions? About how much fluid do you think I need to drain from the system? I see the repair manual calls for a special tool to install the sleeve. How hard is it to remove it from the shaft? Will I have to remove anything else in the speedo assembly besides the cable? Thanks.

 

[Bextreme04]

Eric, can you answer a few questions? About how much fluid do you think I need to drain from the system? I see the repair manual calls for a special tool to install the sleeve. How hard is it to remove it from the shaft? Will I have to remove anything else in the speedo assembly besides the cable? Thanks.

You shouldn’t have to drain anything. I have never tried to remove a sleeve, so I’m not sure. It would probably be best to remove the speedometer shaft to make sure it doesn’t have any issue if you are removing the tail shaft.

 

[texasmike]

Thanks again, I think I’ll give it a try.

 

[Jeff MacQ]

Hey Mike- I just finished a similiar repair on my 83 gmc c1500. Bextreme is spot-on with his info. I pulled the tailshaft extension housing, (4) 1/2" bolts (reinstall at 35 ft lb)
I got a kit off amazon, bushing and seal for 12$. The housing o-ring was harder to find, but I after some effort got delco oem, 3 for $6. There is a great youtube vid for this job at youtube (search 9PIrZDP5xVo or 'tail shaft seal and bushing replacement')
You do have to jack it up fairly high, but its not hard to acess. Loosen (to give an inch of play) the 2 trans mount bolts and jack the transmission up an inch to allow the tailshaft to clear the mount easily upon reinstall. I used a 4×4 under the pan and a pump jack.
Fyi, i only replaced the seal, hoping / gambling that the bushing wasnt the problem. You may want to walk the tailshaft to a local shop to have them remove/replace the bushing, if you are inexperienced with that and want to only do this once.

 

[texasmike]

Thanks for all of this great information, Jeff. Did replacing just the O-ring next to the sleeve/bushing stop the leaking for you? When you pull the extension case away from the output shaft, does the shaft just pull out? I only have 56k miles on my rig and the bushing shouldn’t be worn out. Have you heard that replacing the yoke with one without a hole would also stop the leaking?

 

[Jeff MacQ]

Sorry for the delay, I'm in the process of moving and it has been a tough week.

It seems the seal is holding with no leaks. I replaced the large o-ring that surrounds the housing where it mates with the tranny. My truck / tranny has 105k miles. I saw no o-ring on the output shaft near the speedo gear or governor. You only remove the driveshaft, 4 bolts at the rear. The tranny output shaft does not move or need adjustment. It sounds harder than it actually is, you can do it, the driveshaft is unwieldy but not that heavy, just be careful to not bang it on anything, they dont take side impact well.

 

[Jeff MacQ]

Meant to edit, i replaced the rear seal and as recommended, the tail shaft o-ring.

 

[Jeff MacQ]

Mike, these are the part #s for my 83 gmc c1500 with the 700R4 tranny:

GM Genuine Parts 1358899 Automatic Transmission Case Extension Seal

GM Genuine Parts 8673526 Automatic Transmission Rear Output Shaft Seal​

 

[texasmike]

Hi Jeff.
Thanks for all of the good information and help. I have just a couple of questions if you have the time. Did you have to loosen and move the speedometer assembly back slightly to disengage the gear before pulling the case extension off? Could you tell if the output shaft seal (small O-ring) which goes on the shaft and rests against the shaft sleeve, was missing, damaged or pinched? This is the part that prevents the fluid from running along the splines and leaking thru the metal plug at the end of the slip yoke. My plug must have a rusted out spot on it and leaks only when the drive shaft stops with that spot somewhere in the 5:30 - 6:30 position. I have seen a good video showing how to seal the plug, inside and outside the yoke. The rear case extension seal which the yoke fits thru, is not leaking and was replaced around 4k miles ago. Did you loose much fluid when you removed the case extension? I hope all of this isn't too confusing and thanks for your help.

 

[Jeff MacQ]

Yes, disengaged the speedo cable, comes off simple like a screw top bottle. Didn't see a small o-ring on the shaft & wondered about that. Guess I will look more into that once i'm settled. Didnt lose much fluid, several ounces.
The yoke questions are getting beyond my knowledge / experience -the vid i linked summarizes what i know/ learned doing this job (in a hurry). If the tail housing bushing is bad it can cause/ result in a wrecked seal fairly soon