Hot Rods Ford 8" Rear Leak Question

Hello All. I am hoping you can help me. I have a Mercury with a stock 8" Ford rear. The pinion seal was leaking. Using the factory shop manual steps, I removed and replaced the pinion seal. I used all Ford service tools. I re-installed the pinion nut and checked the rotational toque to make sure that it was in spec with the shop manual. I did not touch the crush washer or internals. Everything was marked before removal so the drive shaft and the pinion yoke are in the same spot as removed. I filled it with gear oil until there was a dribble from the fill hole. No leaks. Then I watched it over about a week.

It is leaking now from the center of the yoke (previously it was around the pinion seal). It is leaking constantly. It looks like the leak is from the pinion nut. I reused the original nut, but did not seal the threads. I don't believe the shop manual said to. When I check new nuts online they have sealer on the threads.

I have seen some posts online that say the threads and Yoke splines need sealer, while others suggest that a static torque setting of 90-125lbs will deal with the issue. It's on the lift at the moment and want to deal with it once and for all.

BTW, the yoke looked unscored but I have a speedi-sleeve for it. Thoughts?

Is it a torque issue or should I pull the yoke, sleeve it, seal the splines and threads, and reinstall?

Thanks everyone!

 

I always put a bit of sealant on both the yoke splines and nut thread.

If the yoke I unmarked then no need to sleeve it.

 

I usually put a thin wipe of sealant on the backside of the pinion nut washer, especially if there is some scoring of the pinion yoke face. Your yoke could also have excessive spline wear.

 

I'd buy a new pinion nut, clean the yoke in the spline area with some brakeclean, put some sealer in there and install the new nut. You need to check the turning torque of the pinion before doing this. I think you need closer to 150 ft lb on the nut.

 

I put sealer on the splines, it stops that leak. A new nut with the pre applied sealer also works.

 

Definitely will speedi sleeve the yoke now and replace nut. My Torque-o-Meter gave me 25 in/lbs of rotational torque when I initially reinstalled. In line with the service manual recommendation. If I keep wheels on the ground I was assuming about 90-100lbs. of static torque. So 25in/lbs rotational translates to 150ft/lbs static? I will try and get a torque reading wheels down, but my gut is its currently < 150lbs. Thanks everyone I really appreciate your help!

 

How tight you get the pinion nut is not really related to the preload. The preload is a result of the thickness of the crush sleeve. If it has used bearings and you get that much preload torque at that little tightness of the nut, you really need a new crush sleeve.

 

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If using the original nut I install blue Locktight on the nut.

 

Thanks, everyone. I took a look again at the Shop Manual, and it says to replace the nut. I missed it and didn't seal the nut when I reinstalled it. Going to order a couple replacement nuts, sleeve the Yoke and redo.
You guys are great I appreciate everyone helping me on this.

 

I recently had a pinion seal go out on the 8" in my M-car. I pulled the whole pinion assembly (keep track of the orientation of the pinion so you can put the gear teeth back together in the same spot, and also keep track of the adjustment shims). I took the assembly to the machine shop to have them crush a new crush sleeve for me - they're tough little buggers. The shop manual says that the preload for used pinion bearings is only something like 10-15 in./lb. rotational torque (you may want to double check that, but I'm pretty sure I set mine at 11 or 12 in./lbs.).