8 3/4 742 case setup questions

[vintage chromoly]

Hello all.
I did the unthinkable today. I took apart my 742 to some degree. I haven't pulled any bearing or races yet.
I've removed the sure grip and ring gear as a unit and the pinion gear with the bearing.

I'm looking to install a new ring and pinion.

Couple questions:
1- do I need new bearing? The exsisting unit was functioning perfectly and the bearings and races look perfect.
2- Do I need to replace the clutch discs? Again, operating just fine.
3- one shim was split in two on the front pinion shims. There were two shims. Can I buy a shim kit?
4- any issues with motive gears? Have my eye on a set from doctor diff.
5- im assuming I'll need a pinion depth setting tool. Is this accurate?
6- any virtue to a steel pinion yoke on a hot street car with no intention of running slicks ever?

I have a nice starrett magnetic base indicator for setting runout and backlash.
Are you guys using a bearing removal tool like a splitter for the pinion bearing and carrier bearings when removing them?

Thanks for any help anyone can provide!

 

[dvw]

Old bearings will be fine if they look good. Shim kits are available. More time than not the existing pinion shim behind the pinion head will be very close. You need a puller to pull the existing pinion bearing off the pinion. Pattern check is still required even with a pinion depth checker. You need a way of holding the unit. You need a dial type inch pound torque wrench to measure preload. And then it's an art.
Doug

 

[vintage chromoly]

I thought preload was only done on a 489 case with the crush collar.

 

[john-9]

Hello all.
I did the unthinkable today. I took apart my 742 to some degree. I haven't pulled any bearing or races yet.
I've removed the sure grip and ring gear as a unit and the pinion gear with the bearing.

I'm looking to install a new ring and pinion.

Couple questions:
1- do I need new bearing? The exsisting unit was functioning perfectly and the bearings and races look perfect.
2- Do I need to replace the clutch discs? Again, operating just fine.
3- one shim was split in two on the front pinion shims. There were two shims. Can I buy a shim kit?
4- any issues with motive gears? Have my eye on a set from doctor diff.
5- im assuming I'll need a pinion depth setting tool. Is this accurate?
6- any virtue to a steel pinion yoke on a hot street car with no intention of running slicks ever?

I have a nice starrett magnetic base indicator for setting runout and backlash.
Are you guys using a bearing removal tool like a splitter for the pinion bearing and carrier bearings when removing them?

Thanks for any help anyone can provide!

1- if you are going to install a new gear,---- yes put in new bearings.
2- yes--- replace the clutch discs if you have the Powerlock type unit-- just take note of how the clutch discs are stacked on your side gear hubs -- they have to be installed/stacked properly to work right
3- you will get shims to set bearing preload and pinion depth with your new bearing kit.
4- nothing wrong with Motive gears -- excellent gear sets.
5- depth setting tool will get you close to the proper pinion shim selection -- but-- the final say on a gear set up is the gear pattern.
6- your stock yoke will be fine .
7-a splitter will work for the pinion bearing ,, the carrier bearings area little tougher to remove
8- use your original pinion shim under the large bearing to for your initial set up with the new gear ,, do a pattern check and adjust the shim thickness till you get a correct pattern -- then do your final set up with the proper pinion bearing preload
9- doesn't matter which type/make of differential you are working on pinion bearing preload is required for all set ups if you want the gear to live.
10-replace the parts needed now,,, 40 + year old bearings and clutch discs not being replaced -- do you really want to do this twice and ruin a new gear in the process to save a few dollars.

 

[vintage chromoly]

Thanks john.

 

[Daves69]

............
http://www.doctordiff.com/

 

[vintage chromoly]

Update:
Ordered all new stuff from the doctor.
Bearings, gears, front seal, clutch pack and upgraded to the made in USA Timkin bearings.

Got the carrier bearings off and took the sure grip apart. The clutches were worn badly.

Parts will be here Saturday.

 

[vintage chromoly]

Oh yeah,
Went with a 3.73:1 cus I'm crazy like that.

 

[Fran Blacker]

I'd put the old pinion in and measure the depth of the old pinion to get a depth to start with. Mopar gears have a number stamped on them like +2 or -1. . If you put the new gear in it should be close to old gear depth. There should be a shim under rear bearing. That shim on new gear would also be a good starting point to work off of.

 

[Fran Blacker]

If you remove the rear bearing without breaking it I would make it a "setup" bearing. You have the center honed out to just slip on the new pinion gear. This way your not pulling the new bearing off if you need to change shims. If you break the bearing maybe you can find a cheap bearing on ebay to make a "setup" bearing.
PS: the rear bearing is the large pinion bearing. Don't know how experienced you are?

 

[vintage chromoly]

If you remove the rear bearing without breaking it I would make it a "setup" bearing. You have the center honed out to just slip on the new pinion gear. This way your not pulling the new bearing off if you need to change shims. If you break the bearing maybe you can find a cheap bearing on ebay to make a "setup" bearing.
PS: the rear bearing is the large pinion bearing. Don't know how experienced you are?

I'm aware.
That is the plan.
I cut the cages off the carrier bearings and used a splitter and puller setup to pull the inner races.
I'm taking the pinion and pinion gear to the local machine shop to have it pulled in one piece and honed for a slip fit to be used for setup.

 

[Fran Blacker]

https://www.summitracing.com/parts/kti-70382/overview/
You can pull tapered roll bearings with a puller like this, may not be the right size. You grab the rollers on large side on the tapered part of puller in center. This forces the roller against the small end of roll and the lip on bearing. Have broken a few bearings but saved a few. Make good setup bearings if you don't re-used them.

 

[Cranky]

1- if you are going to install a new gear,---- yes put in new bearings.
2- yes--- replace the clutch discs if you have the Powerlock type unit-- just take note of how the clutch discs are stacked on your side gear hubs -- they have to be installed/stacked properly to work right
3- you will get shims to set bearing preload and pinion depth with your new bearing kit.
4- nothing wrong with Motive gears -- excellent gear sets.
5- depth setting tool will get you close to the proper pinion shim selection -- but-- the final say on a gear set up is the gear pattern.
6- your stock yoke will be fine .
7-a splitter will work for the pinion bearing ,, the carrier bearings area little tougher to remove
8- use your original pinion shim under the large bearing to for your initial set up with the new gear ,, do a pattern check and adjust the shim thickness till you get a correct pattern -- then do your final set up with the proper pinion bearing preload
9- doesn't matter which type/make of differential you are working on pinion bearing preload is required for all set ups if you want the gear to live.
10-replace the parts needed now,,, 40 + year old bearings and clutch discs not being replaced -- do you really want to do this twice and ruin a new gear in the process to save a few dollars.

The depth setting tool I have tells me exactly where the pinion gear is sitting.....

 

[vintage chromoly]

A friend took the pinion gear and bearing assembly to the shop today and pulled the bearing off intact. Gonna make a serup bearing out of it.
He called and said there were no shims behind the bearing.
I'm picking it up in the morning.
Not sure how there could not have been any shims behind the bearing.
My friend is a retired millwright, so I'm sure he knows what a shim is.

 

[Fran Blacker]

Have you checked behind the cup? On 489 housings you can put Dana 60 rear bearing shims behind the cup. Bearing is smaller in 742 housing? right?

 

[Cranky]

A friend took the pinion gear and bearing assembly to the shop today and pulled the bearing off intact. Gonna make a serup bearing out of it.
He called and said there were no shims behind the bearing.
I'm picking it up in the morning.
Not sure how there could not have been any shims behind the bearing.
My friend is a retired millwright, so I'm sure he knows what a shim is.

Man....I have never torn down a rear end that didn't have a thick shim behind the pinion bearing in any 8 3/4 but I've see stranger stuff happen with Mom's stuff......

 

[Fran Blacker]

Maybe your friend is thinking a shim is only say .003 or so not .028 or more thick?

 

[vintage chromoly]

I hear ya.
I was expecting a .090 shim or so. My buddy is saying the bearing was tight right up against the pinion gear.
I'll find out tomorrow.

 

[vintage chromoly]

Have you checked behind the cup? On 489 housings you can put Dana 60 rear bearing shims behind the cup. Bearing is smaller in 742 housing? right?

If you're taking about the race in the housing, I knocked those out and there were no shims there.

 

[vintage chromoly]

Oddly enough, the gears were quiet as a church mouse and have a nice pattern on the teeth.