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8.8 Diff. Pinion Bearing Preload PROBLEM

13K views 11 replies 8 participants last post by  Lex  
#1 ·
I am replacing my 2.77:1 gears with 3.73:1. I purchased a Summit Racing ring and pinion and installation kit. I removed the shims behind the pinion gear (between gear and head bearing) and they measured .030". I decided to install .030" worth of new shims behind the new head bearing and 3.73 pinion for starters. I replaced the cups for both bearings and a new crush collar. All parts went back in the order which I found them and I verified the assembly against my Chiltons exploded diagram. I have .007" gear lash and a textbook contact pattern as indicated with gear paint.

The instructions said that with new bearings, you should tighten the pinion nut to 125'/lbs, check preload by using an inch/lb torque wrench on the pinion nut and increase torque in 10'/lb increments untill the preload is measured as 25"/lbs on the pinion nut (for new bearings). My Chiltons gives 140"/lbs for drag on a complete assembly after replacing simply the input oil seal.

Problem is this: As I torqued the nut, I frequently checked the endplay on the pinion shaft. Just when the play was totally taken up, the pinion nut felt as though the companion flange bottomed out on the splines. The nut stopped turning and even with a large breaker bar and as much torque as you dare put on the nut, the pinion has NO MEASURABLE pre-load. You can turn it easily with 2 fingers, even after the entire assembly was installed including axles.

Has anyone in the know run into this?

The only fix I can think of is a thicker pinion shaft oil slinger ( the thin washer behind the seal and before the bearing). If I'm correct that the splines have bottomed out, this (thicker oil slinger, or stack of them) would hold the companion flange out from the end of the splines and allow the bearings to preload. Am I on the right track? Is this a common problem???

Jerry
 
#2 ·
I ran into the same problem doing a gear swap for my son.After confirming that the nut wasn't bottoming out,I had to use the handle off of my floor jack to get enough torque to crush the washer.Then i was able to set the preload on the bearings.
 
#3 ·
Holy *&^%? Batman! Your telling me you can put that much torque on the threads and they won't strip! I thought that crush collar looked tough but all my info kept saying it should squish around 150'/lbs and I must have had 225'/lbs on it!

Jerry
 
#5 ·
Jerry, in the Bad Shoe Productions video, the guy had 2 4ft breaker bars and was torquing the crap out of them to get the crush collar to get where he needed it. I bet he put 250-300 ft/lbs on it.

Another option on these is to use a solid crush collar that doesn't actually crush. The guy goes over that in the video.

Good luck.
 
#6 ·
Good! At least I know I'm OK. I was alone and with as much force as I was putting, I couldn't read the torque wrench! It is the preload your after though.

Don't you hate it when your info is so far from the truth? 150'lbs...righhhhht!
 
#7 ·
Yup - you are just starting to crush the crush sleeve - be really careful with this part as it is really easy to over crush the sleeve and then you need to start over again. I don't know why they give torque readings as those are immaterial - you keep tightening it until the rotational torque is whatever the specs are for new bearings - 20-25 inch pounds I think. As you start to crush the sleeve, it will only take about a 1/16 of a turn to start bumping up the rotational torque - I lay on my back perpendicular to the driveshaft with my foot up against some part of the car and a breaker bar and put gradual leverage on it - it will take about every ounce of strength to turn it once all the slop is out of the pinion.

Good luck!!
 
#8 ·
Mine is on jack stands and I was lifting one end off the stand. I'll put it on the floor to get better leverage.
Thanks
 
#9 ·
Your not going to smash the crush sleeve with only 150 ft. lbs. Not sure at what tq it will,but for me it's starts to crush with a 4' cheater bar. Sneak up on the final bearing tq. as you tighten the nut. Can't go past it without getting a new sleeve and starting over.
 
#10 ·
This is from a different vehicle and probably a no no but it works I quote the repair manual " slacken the nut while measuring breakaway torque" yada yada yada " retighten to breakaway torque + 10%" From a "shaguar" manual. You will find that with a big jump in ratio like that you'll have to fart around to get the correct clearance. Bob
 
#11 ·
I had to use 2*4' breaker bars, and I'm estimating it took close to 400 ft-lbs to get it torqued - one bar against my stomach, both arms pulling the other bar toward me.
Instead of "check every 10 ft lbs" I would suggest scribing index marks on the but and on the pinion flange.

IT GOES QUICK AT THE END!!! My preload went from "nada" to "perfect" with less than 1/16" of rotation measured on the outside perimeter of the nut. Really - fight the urge to "reef it a quarter turn and see".

good luck!
 
#12 ·