Loose Pinion Nut

bhuff30

Founding Member
Dec 11, 2001
6,037
35
129
Olathe KS
The pinion nut on my 97 GT keeps backing off. The previous several time I installed the nut, I did everything correctly: new crush collar, new pinion nut and torqued the pinion nut to get the proper drag on the pinion.
This time, I am not wasting so much time. I am thinking 100 ft*lbs of torque and plenty of loctite on the threads. What do you think? Is 100ft*lbs the highest I dare to go to avoid crushing the collar further? Blue loctite in case I ever need to take it apart?
 
  • Sponsors (?)


Tell us HOW you measured the pinion pre-load. Why is this important? Because in the rear end work I have done, it takes far more than 100 foot pounds to turn the pinion nut to establish the correct pre-load.

Also, blue loctite won't cut it. Use the red loctite. However, if you are using a NEW pinion nut, no loctite is needed as the nut already has it applied.
 
The last time I tightened the pinion nut, I ended up over-crushing the crush collar (150ft*lbs I recall?). I took the carrier out, replaced the collar with a new collar, installed a new nut and torqued the nut until I got the desired rotational pinion drag. Drag was measured by an in*lb torque wrench with only the pinion installed. I did the best I could with a click-style torque wrench (I don't own a bar style yet). Even though it was a new nut, the nut still came loose after just 5k miles.
I'll get some red loctite and re-use the old nut. New nuts haven't been staying in place for me, so I see no reason to spend money and try again. So do you think 100 ft*lbs will work well? Tighter seems more likely to stay in place, but I obviously don't want to risk crushing the collar more.
 
I'm not sure we fully understand what's going on. The pinion nut is NOT tightened to a specific torque reading. The ONLY thing that matters is the pinion pre-load. Even if the pre-load is too low, the nut should not back out.

Therefore, I think there's something else going on. For example there's a part missing (thrust washer). Orrrrr the replacement bearings were not fully seated in the 1st place. Which if true would mean that the nut isn't backing out but the bearings are moving together.
 
I fully understand that pinion drag (and hence preload) is dependent on the amount the crush collar is crushed, and not torque on the pinion nut. I demonstrated this in my prior posts. I am certain the rear end is assembled properly. It worked great for a while, but I have slowly felt it getting looser and looser lately... coinciding with some hard launches and powershifts.
Yes, the proper way to tighten the pinion nut is to tear down the entire rear end, replace the crush collar, install a new pinion nut and crush to achieve the proper pinion drag.
OR: Another way that would work but won't be found in the ford service manual is to use loctite and torque the pinion nut to a value below that where the crush sleeve would be re-crushed. This only requires removal of the 4 driveshaft bolts, so I can spend more time with my family than under the car. After all, pinion pre-load is set by the crush collar and I have a good setup already. Anyway, I will use some red loctite and torque to 100 ft*lbs. I am just guessing I dare not go higher or the collar will be crushed further and I will have to teardown and do the whole job.