T-56 Magnum owners...can't get mine to stop leaking!

[DropTopSnake]

So we put a Magnum (American Powertrain) in the 04 cobra about 4 months back...had the stock cobra driveshaft shortened and balanced after making sure what length we needed after mounting the Magnum.

We had all the same clearance issues as most others have posted about, nothing a bit of grinding and BFH didn't take car of.

After initial install...everything felt good. No weird vibrations, shift 10x better than the stock T-56...but the infamous leak from the rear seal where the yoke goes into tranny rear seal has me screwed. Oh yeah, we also installed a brand new upgraded yoke that we got from American Powertrain also.

We've pulled the driveshaft and replaced the rear seal twice now, with the upgraded metal reinforced Duralast branded seal that American Powertrain recommended. Still leaking after I take the car for drives.

It is only happening when driving the car it seems...as I can get under there and wipe up the residue and it doesn't come back until driving again. Seems to be worse the more I stomp the go fast pedal...which is logical. My driveshaft angle doesn't seem to bind the seal, and I only have about 2mm of yoke shaft showing out of the seal...so it is seated in the rear of the tranny well. Fluid level has been checked everytime I'm under there and all is good there (after adding some for top off more than once after a couple weeks of leaking after some datalogging, etc)

Hoping to not have to pull the tranny again and send back for warranty...

Might try and get my gopro mounted under there today and see if maybe I can get some video to see exactly what seems to be going on.

Any advice or suggestions are appreciated if you've got any knowledge to share.

Thanks in advance for your time

 

[SlowSVT]

Call D&D or Liberty

 

[P49Y-CY]

just how much is it leaking?

 

[arodsvt]

I have the exact same issue......

 

[arodsvt]

I have the exact same issue......need to make time to drop it off.

 

[DropTopSnake]

As far as "how much"...hard to actually quantify, but it's more than enough to be a problem. It gets "flung" all over the place under there and ends up having runs and drips all the way down both of my full length sub frame connectors, and slightly puddles up on top of the Mac prochamber midpipe. After parking in garage, I can put a plastic lid down there to catch the main drips and it looks like a little less than about 1oz of fluid by morning, then doesn't leak at all until next time I go joy drive a bit. But that 1oz doesn't count for all the Amsoil that has been flung all over the undercarriage and dripped onto road while actually driving.

 

[SlowSVT]

I wonder if the OD on your yoke is a little undersize where the seal properly. Is the surface where the seal sits on the shaft machined smooth? You stated there is a 2 mm gap from bottoming out the shaft which is kinda close. If the seal is riding-up on the fillet where the shaft meets the yoke it won't seal. It leaks when the oil is flailing around when you dive it.

I will get you the OD of the yoke shaft on my Magnum later today and post the measurement

 

[DropTopSnake]

You might be on to something slowsvt. No worries and no rush, but if you can get me your yoke shaft OD, that would be fantastic. The surface of the yoke seemed nice and smooth if I remember correctly...

Thanks in advance for your time and effort my man...

 

[DropTopSnake]

Also brother, what specific brand yoke did you go with? I saw some of your old posts about this from 2014...

 

[DSG2003Mach1]

You might be on to something slowsvt. No worries and no rush, but if you can get me your yoke shaft OD, that would be fantastic. The surface of the yoke seemed nice and smooth if I remember correctly...

Thanks in advance for your time and effort my man...

ya he really might be, when I dropped my magnum and the driveshaft that came in the kit (previous owner bought it, not sure where from) and when I pulled the DS out it fit that seal so well there was a "pop" when it broke the suction with the seal

 

[SlowSVT]

Also brother, what specific brand yoke did you go with? I saw some of your old posts about this from 2014...

Here is one of my post with the info you need.

http://www.svtperformance.com/forums/showthread.php?1055325-T56-Magnum-Slip-Yoke


I am really beginning to think the seal is riding-up on the corner fillet. That will require shortening the driveshaft further (3-4 mm gap vs. 2mm).