I am putting together a 12 bolt axle from an Impala- first axle rebuild i've done before On tightening the pinion nut with an impact gun i can't seem to get the play out of the pinion (it can still be lifted up/down 1/16"), i have a new crush sleeve in place. The bearings look ok but i'm wondering if there not Has anybody come across this problem before? Also i bought the axle but it was already stripped Many thanks.
most impacts will not be strong enough to crush it you should not use an impact anyways ...thinkabout it...while the bearings are loose you're just banging them around/causeing damage ...most do the setup without seal......... support the rear end with the yoke in a large vise use breaker bar with an extention pipe handle do it slowly ..most do it by feel ....but there are specs for new&used bearings...lite oil on them... motor manuels are your friend..........
Thanks for your reply. I was under the impression from checking out these instructions http://www.hotrod.com/techarticles/drivetrain/gm_12_bolt_differential_install_guide/index.html that that an impact gun was best as they snapped there breaker bar! It does seemed to be wound down pretty tight from the impact gun yet still has a lot of slop.
having the rear end fail on you on the road is no fun get a friend/make a new one ...get help not by using a article like that>they are trying to sell a tool explain more fully what you are doing to the rear end ??? how far apart was it ??? these are one of the harder rears to do
I use a 3/8 plate that bolts to the yoke and has a 4 ft 3/4 bar welded to it ,I then find a spot to wedge the breaker bar,a spot on chassis etc, and pull on the bar. I have broken snap on breaker bars, and bent the bar on some rears you want around 20-25 inch pounds of drag on new bearings slight drag on used
You can use an impact wrech ,but you still should support the pinion yoke so it the gun doesn't "impact" on the gears.New guns rated at 450 ft lbs of torque will do it with 130 plus psi of air.Go carefull once the pinion starts to tighten up as it's all to easy to overtighten the bearings.Yeah,about 12 in lbs for used bearings,25 for new ones.And do use a small torque wrench,don't quess.
Thanks for the replys. Just looking to reassemble it really- it came with gearing 3.38:1 with little wear- this suits my 55 truck and th350 fine. It was stripped completely except the posi unit which was all intact. The pinion also had the large bearing still in place. I would think its either knackered bearings or i'm just not tightening the pinion nut tight enough yet! The axle is out of the truck. Thanks.
Pretty common problem, we've talked about it before. I usually put the crush sleeve in a press and put enough pressure on it to get it to give. Then you can put it on the pinion, assemble the rear end and it will set up right. Larry T
Hey i got it sorted thanks to the crush sleeve advice! It was down to the new crush sleeve which wouldn't crush! So i put the crush sleeve in that came with the axle and it tightened down with the impact gun lovely. Is .004 - .005 inch too tight for the backlash?
Putting the old crush sleeve back in is not really sorting it. The crush tube is intended to be a one use item. Basically its purpose is to prevent the nut on the pinion from coming loose. On a rebuild it is intended that you replace it so that the correct tension on the nut is acheived to hold it in place and keep the bearings at their correct preload. The correct pre-load is acheived via the shims not the crush sleeve. Bearing pre-load is done with out the seal as that will result in extra drag on the pinion shaft and give a false reading on bearing preload measurement. Once that is correctly set then install seal, fit crush sleeve and nut. If that nut moves (loosens) which it is more likely to do, given that the old crush tube is being used, then the pre-load will be lost. This can result in movement of the pinion fore and aft and deflection sideways. All of this will add up to premature wear and possible failure of the crown wheel and pinion set. You should use the new crush tube as intended. Putting the crush sleeve in a press is not a good idea either as you have no idea what amount of deformation has taken place. Should allow the crush to take place in situ as intended.That can be a real chore in terms of holding the pinion whilst you wind the nut down.
Yep, most rearends I've set up call for .008, some say + or - .002. But you're still out of spec there. Larry T
Tightening the pinion nut with an impact gun? I would never even consider it.Too easy to overtighten,imparts a brinnel surface in the bearing and generally not within any torque spec at all.Guess if you were just doing it in a truck for offroad use only but for something I had to rely on far away from home...nope.
I too am with most of you with the "Impact Gun " . That is NOT the tool to do rear end set up with ! Use a good socket , 1/2" breaker bar and a pipe and turn it slowly to get it where it's suppose to be and always check the tracking and use a dial indicator. Your best bet it to have someone show you how to set one up . That is one of those things that is best to learn from someone else . Yes you can read a dealers manual but I wouldn't really take an article to set a rear up . It's just my opinion and I have set up many ring and pinions over the years ! Other than that just take your time and don't rush it . You will know if it's set up right when you drive down the road . Good Luck ! Retro Jim
As for the backlash spec what you need to bare in mind here is that the factory spec is for new gears. Once they bed in and have been used for a while the lash will open up to some extent. The amount depends on the number of miles on the gear set , type of use etc. As they say an ounce of prevention is better than a pound of cure. In this case before a used gear set is dismantled a lash reading should be taken. That is the spec you set it to. Otherwise the meshing pattern will be incorrect. You probably have lost that opportunity. More importantly here is the need to mark up the crown wheel and pinion to achieve a reasonable pattern. If it marks up and shows the pinion is bearing on the crownwheel tooth near the outer part of the tooth then crown wheel is at risk of having the teeth breaking off. It should bear closer toward the inner end of the tooth. As load is applied the mark tends to move along the tooth toward the outer hopefully somewhere about the middle of the tooth. I hope this makes some sense. Often the manuals have pictures of these meshing patterns which make what I'm saying clearer.
fredeuce, is giving you good advise. Go to your local library and find an old motors manual copy the pages on setting up rear end gears. esp. the pic's on gear marking. Any arts and crafts store will have oil paint tubes Prussian blue is trad but any dark color will work . .004 will work for backlash. doesnt matter what rear you copy the ideas on gear set up always apply. plane trains automobiles
The last set that I tried to slip by at .005, whined when they warmed up. So I don't set them up that tight anymore. I'm not an expert, but I've set up 5-10 rearends a year for the last 20 or so years. In fact I've got a set to finish up for a rock crawler today. Larry T
All of the Chrysler rear diffs I have done were .005-.008 backlash.Better to be 7 or 8 than the lower.....
Thanks again fellas. I now have backlash at between .008 and .009 inch Its assembeled now with loctite on the pinion nut- and i'm not sure but think the crush sleeve may have been new anyway? Also the richmond instruction dvd i followed showed the use of an impact gun. I used some yellow stuff on the teeth to check the pattern and it looked good according to the instruction dvd. I will keep a close eye on things for the first 1000 miles or so.
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