7.25 axel new pinion bearings set up

[Chuck Bushey]

I had a growl in the differential and pinpointed it to the front pinion bearing. Got a new bearing set and working to get them installed. Using the same pinion and ring gear. The pinion is marked as -0 so I assumed I didn't need any change in spacers. Specs say the pinion nut should be torqued to 240 ft-ibs and should have a preload drag of 15-25 in-lbs. With nut tight with wrench but not torqued I have 35 in-lbs of drag. Prior to disassembly I had about 10 in-lbs of drag. I'm afraid to try to torque to 240 ft-lbs concerned the pinion might not turn. Anyone have any comments / recommendations.

Happy 4th to you all!

 

[john-9]

first thing to try ,, when torquing the pinion nut go in steps of say 50 lbs/ft and then give the yoke a couple turns forward and reverse , this lines up the bearings and their races then go to 100lbs/ft and turn the yoke and so on to the final torque . if at say 100 lbs/ft you have to much preload you are going to have to replace the crush sleeve and set the preload to the 20-25 lbs/inch for new bearings. there is no real torque spec when using a crush sleeve ( although they say 175 lbs/ft minimum to crush the sleeve ) as once the sleeve is crushed to the correct preload spec you are done you can pull up to 300-500 lbs/ft to crush that sleeve,,, now if your diff uses shims to set the pinion bearing preload then you have to add some shim to bring the preload to spec then torque the nut to the 240 lbs/ft spec.

 

[19DART66]

I don't know about the 7 1/4 rear axles after 1970.
But the 1969 and back I do know use a shim pack to set the pinion bearing preload, and that's why it is calling for 240 lbs/ft to set the preload on the bearings to 15 to 25 lbs/inch.
Just like the 8 3/4, the 741 and 742 cases used shim packs and the 489 used a crush collar.

 

[Chuck Bushey]

Thanks guys, your suggestions are what I am doing. I should have said this is a 66 so it uses spacers and not a crush sleeve. Today I am going to go through these steps again as well as rechecking the backlash and depth pattern. I took all measurements prior to teardown and all were right within specs and so I figure I wouldn't need to change or adjust the spacers - assuming the bearings would be essentially the same thickness as the old. Guess I'll see what happens today. At 72 I don't have a lot of energy or strength and will actually need someone to come help me pull the correct torque if I can get it to that point.

 

[oldkimmer]

Do u have the new cups in all the way? Is the inside bearing pressed on the pinion all the way? Kim

 

[Chuck Bushey]

Okay, this project is kicking my butt! In hindsight I should have tried to take some kind of measurement on the depth of the pinion in relation to the case so I would have had a starting point. Even though I used the same brand bearings (Timken) and the same exact part number, they are not the same. To the last question above, yes the races are fully seated in the case. Just for recap, this is a '66 Barracuda with 293 gears in a 7-1/4 differential.
My new set of questions: Does anyone have a way to set the initial pinion depth on this when you don't have the setup tools referred to in the manual? I need to have that starting point in order to get this thing focused in. Currently I have .098 depth shim - original was .090 and I have added .008 in order to get the backlash within specs - currently my minimum is .0055 and the largest one is .008 so that appears to be good to me, but the pattern keeps coming out as needing to move the ring out from the pinion but when I do, backlash goes out to lunch. Any help you can provide is welcomed. I'd say I'm pulling my hair out over this but I don't have any to pull out.

 

[Sterling]

If you were just changing the bearings and not the gears you should not have had to change the pinion depth. You might have to add or subtract shims to get the pinion bearing preload correct. Not sure how the backlash is adjusted, but I would put the pinion depth shim that came out back in and adjust the backlash. There is a standard measurement from the center of the carrier bearing housing to the pinion for pinion depth. I do have a universal depth gauge, but have not tried it on a 7 1/4" rear. If I don't have the adapters in my depth kit, I try to start with the removed shim from the old gear set to start.

 

[Chuck Bushey]

Thanks Sterling, that is my plan for the morning - to go back to the original shim for depth, and then get the preload again. The problem with preload is that .094 shim gives me 25 - 30 preload and .095 gives me 10 - 15, the spec is 15 - 25. According to the manual, back lash is set by moving the ring in or out from the pinion - shifting shims from left side to right side and vice versa to obtain spec. I though that I had done that originally but the pattern wasn't correct so then I started making adjustments to get the pattern correct and of course that shifts all the other measurements off.

 

[Sterling]

I think that you are doing what I would do

 

[Chuck Bushey]

I realize this is now 3 months since the last post on this thread but since I started it I felt it necessary to update the final results of this project. After going back to the original setup and still not getting the proper results, I ended up starting completely from scratch and went through the step by step procedure. The new bearings, although exactly the same part number and brand they did not match up exactly to the originals. So I ended up having to redo the complete pinion setup. Since shims are not available for this axel I ended up purchasing Shim Stock off Amazon and made my own shims. I got a pack of several different thicknesses and made up my own combinations - a lot of trial and error before I got the proper Depth setting. Then I had to make new shims for the preload, because that bearing was completely different as well - finally got the correct preload. I did also have to adjust the side to side bearings - fortunately I had a stack of those shims and was able to adjust from one side to the other. Long story short I finally got the correct pattern and got everything back in place after being gone for a month and a half of that duration. Yesterday I took it out for the first time since and I have no noise and everything appears to be fine. Thanks all for your feed back and inputs. I think the moral of the story is if changing anything, start over from scratch and begin anew, and if you don't have an original setup tool, plan on being patient with lots of slow breathing.