Slant Six Forum
https://slantsix.org/forum/

7.25 question
https://slantsix.org/forum/viewtopic.php?t=36242		 Page 2 of 3
Author:  dakight [ Sat Sep 12, 2009 2:04 pm ]
Post subject: 
I just went out to look for markings on the pinions. The old one only has an "A" stamped into the face of the pinion but the is a 2.127... stamped on the shaft. The new pinion has 2.064 written with a paint pen on the face of the pinion. That would mean the difference is .063 thousanths, or .000063... too small a difference to be significant it seems to me.

The backlash is .011. I reran the pattern and I can see the gray shadow appearing. On the coast side it is centered but way high on the tooth which, if I read the pages correctly means the pinion is shallow and needs more shim. The drive side is also high on the tooth and pushed out toward the fat end (heel).
Author:  RustyRamcharger [ Sat Sep 12, 2009 4:43 pm ]
Post subject: 
Quote:
I just went out to look for markings on the pinions. The old one only has an "A" stamped into the face of the pinion but the is a 2.127... stamped on the shaft. The new pinion has 2.064 written with a paint pen on the face of the pinion. That would mean the difference is .063 thousanths, or .000063... too small a difference to be significant it seems to me.
That dimension is the measurement from the face of the gear to the plane of the centerline of the axle, as measured perpendicular to the centerline of the pinion. The new pinion gear is machined so that it should be 0.063" closer to the axle than the old gear. i.e. whatever shim pack was installed with the old pinion should be increased by 0.063" (1/16") and the new pinion gear will be located in the same place as the old one. WOW! That's a lot! Sometimes the pinions are marked with "+0.nnn" or "-0.mmm", which indicates deviation from nominal in thousanths of an inch. Again, take the difference and adjust the shims by that amount.
Quote:
The backlash is .011. I reran the pattern and I can see the gray shadow appearing. On the coast side it is centered but way high on the tooth which, if I read the pages correctly means the pinion is shallow and needs more shim. The drive side is also high on the tooth and pushed out toward the fat end (heel).
That's consistent with the 0.063" difference in the gears. Add some shims and watch the pattern change. You'll have to back off on the backlash a bit if the pinion has to move that much. If you saved or measured the original shim pack, just add 0.063" to that thickness.

Ken
:-)
Author:  RustyRamcharger [ Sat Sep 12, 2009 4:48 pm ]
Post subject: 
Quote:
This is the newer style diff with the screw type side adjusters. No shims are used on the differential; only on the pinion.
Oops...I didn't reat the entire thread. My latest FSM with the 7.25 is 1970, which requires a spreader tool.

What year did the screw adjusters come into use?

Ken
:-)
Author:  dakight [ Sat Sep 12, 2009 9:57 pm ]
Post subject: 
I'm not sure, but this one came out of either a 73 or a 74 Duster.
*EDIT*

I have the original shim which I measure with a caliper at .027. If I add .063 then I would need a shim pack of .090... that's a very thick shim pack!
Author:  RustyRamcharger [ Sun Sep 13, 2009 4:02 am ]
Post subject: 
Try four 0.020" and a 0.010", unless you have a thicker one. Try to minimize the number of shims. Install the thinest shims so that they are sandwiched by the thickest ones.

Are you using a set-up nut and torquing the pinoin nut with each iteration?
You'll destroy the installation nut because it is self locking. The last time I did a set-up I made a nut using my Shoptask 3-in-1 machine, and case hardened it with Kasnit. It worked well.

Ken
:-)
Author:  dakight [ Sun Sep 13, 2009 4:15 am ]
Post subject: 
I'll give it a try, thanks. I'm using the old nut and saving the new one for the final installation.
Author:  dakight [ Mon Sep 14, 2009 7:35 pm ]
Post subject:  Getting Closer
Here it is with .087 in shims and .012 backlash.

Drive Side:
Image

Coast Side:
Image
Author:  RustyRamcharger [ Mon Sep 14, 2009 8:47 pm ]
Post subject: 
Drive face is low and toward the toe end, while the coast side is low and toward the heel end. This combination indicates that the shim is too thick. Try removing the original 0.027" and adjust the backlash to ~0.006".

Ken
:-)
Author:  dakight [ Tue Sep 15, 2009 5:17 am ]
Post subject: 
I was thinking I had too much shim. .006 seems kind of tight for backlash, but I'll give it a try. Thanks.
Author:  dakight [ Tue Sep 15, 2009 4:06 pm ]
Post subject:  Heel and Toe
Latest iteration, .064 shim, .006 backlash.

Coast Side:
Image

Drive Side:
Image
Author:  RustyRamcharger [ Tue Sep 15, 2009 6:31 pm ]
Post subject: 
The coast face is still low and at the heel. The drive face looks to be low and toward the toe, but the lighting and excess marking compound make it hard to see. Try removing another 0.020" or so. Keep the backlash at ~0.006", and try to use more contact pressure on the gears when you rotate them. Putting a bar or pipe through the yoke will make it easier to turn. A hardwood stick can be wedged between the housing and differential case to provide extra friction.
Ken
:-)
Author:  dakight [ Tue Sep 15, 2009 7:16 pm ]
Post subject: 
I went ahead and took out another .009, the pattern is higher on the tooth now. It covers about 2/3 the width of the tooth skewed to the toe on the drive side and toward the heel on the coast side. It's too dark now to get good photos so I'll look at it again tomorrow. I really appreciate your guidance.
Author:  dakight [ Wed Sep 16, 2009 3:18 pm ]
Post subject: 
At least you can see the pattern now. This is with .055 shim thickness and .012 backlash.

Coast Side:
Image

Drive Side:
Image
Author:  RustyRamcharger [ Wed Sep 16, 2009 5:01 pm ]
Post subject: 
You're getting there. The ideal pattern will be centered on both faces. Having it centered on the drive face is more critical than on the coast face. Try removing another 0.015", and set the backlash to ~0.006".

Ken
:-)
Author:  dakight [ Fri Sep 18, 2009 6:10 pm ]
Post subject: 
Here's the latest. Shim pack is .040 and backlash .006.

Coast Side:
Image

Drive Side:
Image
Page 2 of 3 All times are UTC-07:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/