Drivetrain T5 leak - output shaft when on an incline

stangman16 · Jul 16, 2021

I have a T5 in my '66 mustang which leaks through the output shaft when the car is on an incline. Had it towed, and it leaked loading and unloading while on an incline - practically poured out that rear seal. Rear seal was replaced some time ago and the appears to be no leak while the car is level and running..

I had bought this off someone who had supposedly rebuilt it and I ended up breaking a dog tooth and replaced it myself using a t5 rebuild book many years ago.. didnt notice any missing parts or have spare parts afterwards. All gears work fine now too.

Not sure if this is a WC or non-WC trans. Attached is a pic of the inside i had taken.

Is there something possibly missing inside the trans that I need to look at which should block fluid from draining out the output shaft while on an incline?

Rdub6 · Jul 16, 2021

Have you replaced the tail shaft bushing, or just the seal?

Mustang5L5 · Jul 16, 2021

Was this T5 overfilled? The only thing that prevents the T5 from leaking out the rear is the tailhousing seal. There is a short and a long one, and it's possible that if the long one is used and the car is low, that the driveshaft does bump into it damaging it and causing a leak. Was the seal installed with some grease where the driveshaft rides against it?

The bushing inside will keep the output shaft from wobbling too much, but when the vehicle is static, the seal against the driveshaft yoke should still contain the fluid inside the trans.

When these transmissions are built and sold new, there is a plug that is installed on the mainshaft that fits into the bushing at the end. WHen the trans is installed at the factory, the driveshaft pushes this seal in. At this point it's no longer needed. When a virgin T5 is rebuilt, you'll usually find this black rubber seal on the mainshaft, but it does nothing to prevent leakage once a driveshaft is installed.

stangman16 · Jul 16, 2021

Rdub6 said:
Have you replaced the tail shaft bushing, or just the seal?

I have replaced the seal, havent touched the bushing. I suppose I could change that as well.

stangman16 · Jul 16, 2021

I filled the trans to where fluid starts to come out of the fill hole while the car is level.

I believe i have the short seal installed and I dont think I had used any grease where the driveshaft rides against it.

Are you thinking the seal got damaged?

On a side note, the driveshaft is the same one that went into my 4spd toploader, no changes were made to it or the yoke when I swapped to this T5.

Mustang5L5 said:
Was this T5 overfilled? The only thing that prevents the T5 from leaking out the rear is the tailhousing seal. There is a short and a long one, and it's possible that if the long one is used and the car is low, that the driveshaft does bump into it damaging it and causing a leak. Was the seal installed with some grease where the driveshaft rides against it?

The bushing inside will keep the output shaft from wobbling too much, but when the vehicle is static, the seal against the driveshaft yoke should still contain the fluid inside the trans.

When these transmissions are built and sold new, there is a plug that is installed on the mainshaft that fits into the bushing at the end. WHen the trans is installed at the factory, the driveshaft pushes this seal in. At this point it's no longer needed. When a virgin T5 is rebuilt, you'll usually find this black rubber seal on the mainshaft, but it does nothing to prevent leakage once a driveshaft is installed.

Rdub6 · Jul 16, 2021

stangman16 said:
I have replaced the seal, havent touched the bushing. I suppose I could change that as well.

The bushing doesn’t keep the fluid in, but a worn out bushing will cause seals to fail pretty quickly.

General karthief · Jul 16, 2021

I'd try a new yoke and seal,

Mustang5L5 · Jul 16, 2021

If you grab the yoke of the trans, is there any up/down/side to side play?

If the bushing is failed, it will wobble and destroy the seal

stangman16 · Jul 16, 2021

Mustang5L5 said:
If you grab the yoke of the trans, is there any up/down/side to side play?

If the bushing is failed, it will wobble and destroy the seal

Just got home and checked, it is the long seal, and the driveshaft seems to be slightly compressing it. I will change it for the shorter seal. When i touch the seal (the boot part) fluid leaks out. There is a slight wobble when i grab the yoke. Looks like you all figured out the problem. Thanks!

How do you get the bushing out?

7991LXnSHO · Jul 16, 2021

There is a slick tool, or you can pull off the tailshaft. The tool is worth it.
Here is an Aussie changing the bushing on some transmission.

View: https://youtu.be/4vAuDKDV-ok

stangman16 · Jul 17, 2021

Having a hard time finding the right tool and bushing installer. Found one that said for GM T5, would this work? Not sure of the differences in this area between Ford and GM. I know the shift area locations were different...

Rdub6 · Jul 17, 2021

stangman16 said:
Having a hard time finding the right tool and bushing installer. Found one that said for GM T5, would this work? Not sure of the differences in this area between Ford and GM. I know the shift area locations were different...

I’m not sure what stage of disassembly you’re in, if any, but I pulled the trans out. I removed the tail shaft and brought it to a shop to remove the old bushing and press the new one in. Cost me about $30 bucks!

Mustang5L5 · Jul 17, 2021

Is it the tool in this thread?

Need to replace the output shaft bushing on your T5? Here's the tool to get.

I drove it flush since that's where the old one was. IIRC, the tool doesn't quite get it there, but just put something about the right size over it and tap it a few times. Other than that, the tool works great.

www.stangnet.com

manicmechanic007 · Jul 18, 2021

Make sure it is not the air pisser hole in the yoke that is leaking. I assume you've checked the basics like seal condition yoke diameter and bushing clearance and the garter spring is there. You will see pros like me put real thick grease on the splines. The ford stuff is teflon driveline grease XG-8A. You could try one of the splined rubber washers like Ford used on the AOD-E yokes in the late 80's. I have had to remove the yoke and braze up the pisser hole on the bitchy ones

zookeeper · Jul 18, 2021

Inspect your yoke for grooves worn into it. If it has them, a speedy sleeve will make it good as new.

General karthief · Jul 18, 2021

zookeeper said:
Inspect your yoke for grooves worn into it.

OMG @Noobz347 look another one, ahhh, after reading it a couple hundred times maybe not, too hot out, can't make up my mind

stangman16 · Jul 19, 2021

Pulled the driveshaft and the yoke is trash. Fluid is leaking out the back of the yoke and it is worn with grooves on the surface. I will replace the yoke, u joints and bushing inside the tailshaft.

I notice I have about 3/4" from the yoke to rear housing - is this sufficient or will I need to have the driveshaft shortened?

Thanks again!

manicmechanic007 · Jul 20, 2021

3/4 is great needs to be 1/2 at least

Drivetrain T5 leak - output shaft when on an incline

stangman16

Active Member

Attachments

Rdub6

So while I wait to figure out my rear end issues

Mustang5L5

That is…until I whipped out my Bissell

stangman16

Active Member

stangman16

Active Member

Rdub6

So while I wait to figure out my rear end issues

General karthief

wonder how much it would cost to ship you a pair

Mustang5L5

That is…until I whipped out my Bissell

stangman16

Active Member

7991LXnSHO

wanna catch the space herp

stangman16

Active Member

Attachments

Rdub6

So while I wait to figure out my rear end issues

Mustang5L5

That is…until I whipped out my Bissell

Need to replace the output shaft bushing on your T5? Here's the tool to get.

manicmechanic007

zookeeper

General karthief

wonder how much it would cost to ship you a pair

stangman16

Active Member

manicmechanic007

Similar threads

Drivetrain T5 leak - output shaft when on an incline

Active Member

Attachments

So while I wait to figure out my rear end issues

That is…until I whipped out my Bissell

Active Member

Active Member

So while I wait to figure out my rear end issues

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

Active Member

wanna catch the space herp

Active Member

Attachments

So while I wait to figure out my rear end issues

That is…until I whipped out my Bissell

wonder how much it would cost to ship you a pair

Active Member

Similar threads

Privacy & Transparency

Privacy & Transparency