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7.25 question
https://slantsix.org/forum/viewtopic.php?t=36242		 Page 1 of 3
Author:  dakight [ Sun Jul 12, 2009 2:19 pm ]
Post subject:  7.25 question
When I pulled the bearing caps I was careful to keep them separated side to side, though I have no idea if it matters. However, I forgot to note their orientation. It seems that there is one flat side and one rounded side. The hole for the adjuster lock is closer to the flat side. They will physically fit either way but which is correct; flat side toward the carrier or toward the axle? I'm guessing axle, but I really don't know.
Author:  dakight [ Sun Jul 12, 2009 3:22 pm ]
Post subject:  Gear Pattern- First Try
Here's my first try at marking the gears. The pinion depth shim is .029, the original depth from the previous gearset. The backlash is set to .010; Motive Gear recommends .008 - ,012. The pattern isn't as clean and well defined as I would like but I think it tells me than I need to use a little less shim, maybe .025.

Image
Author:  dakight [ Mon Jul 13, 2009 2:18 pm ]
Post subject: 
bump.
Author:  james longhurst [ Mon Jul 13, 2009 3:51 pm ]
Post subject: 
I've not pulled a 7.25 down before, so I'm no help with the bearing caps. From what I can tell on the pattern though, it looks like the marking compound is being wiped off the outer portion of the gear teeth like the pinion is sitting a bit low in the carrier. Looks to me like you could use a little more shim.
BTW, what gear are you running on that Sure-Grip?

-James
Author:  dakight [ Mon Jul 13, 2009 4:11 pm ]
Post subject: 
It's a 3.55 from Motive Gear. If I understand it correctly it should set up exactly like an 8.25 if that's any help.
Author:  james longhurst [ Tue Jul 14, 2009 9:30 am ]
Post subject: 
If the bearing adjusters are like the ones on the 8.25 axles I've done, the thread into the bearing caps/saddles like a big bolt. If that's the case I doubt they would fit if you had them mixed up. I'd think they are like main caps in and engine block. They may physically fit, but will not align properly. If you don't have a fsm I can dig mine out scan those pages for you that pertain to that axle. Maybe the pics will help. I have '63 and '78 model manuals.

-James
Author:  dakight [ Tue Jul 14, 2009 1:04 pm ]
Post subject: 
That would be very helpful. Mine is a late one so the section from the 78 should be perfect. I appreciate it!
Author:  james longhurst [ Wed Jul 15, 2009 7:01 am ]
Post subject: 
Email sent.

-James
Author:  dakight [ Wed Jul 15, 2009 6:01 pm ]
Post subject: 
Thanks!
Author:  dakight [ Sat Jul 18, 2009 4:21 pm ]
Post subject:  Second Try
Backlash .010, pinion shim .015

Image

Any thoughts?
Author:  RustyRamcharger [ Sat Jul 18, 2009 6:05 pm ]
Post subject:  Re: Second Try
Quote:
Backlash .010, pinion shim .015

Any thoughts?
You're taking the photo straight-on. You need to take 2 photos, one showing the drive face and the other showing the coast face. From what I can make out, the pinion needs deeper engagement (thicker shim).
Don't worry about fine-tuning the backlash until you have the engagement pattern centered over the length of the ring tooth.

Ken
:-)
Author:  dakight [ Sat Sep 12, 2009 9:45 am ]
Post subject:  Take 45
Well, the weather has finally started to cool a little bit and the garage is bearable. Here's my most recent attempt:

First the coast side pattern:
Image

And the drive side pattern:
Image

These are with an .020 shim.
Author:  RustyRamcharger [ Sat Sep 12, 2009 11:56 am ]
Post subject: 
The coast side looks like its centered along the length of the tooth, but up high. I can't really make out a pattern on the drive side. You have way too much marking compound on the coast face and not enough on the drive face. What you are looking for is a grey area where the pressure of the gear contact has pushed the marking compound away, exposing the metal surface. As in the old Brylcreem commercials: "A little dab'll do ya". You can use a cut-up body filler spreader, or a piece of a bleach bottle to spread and relocate the marking compound.

How much backlash is the dial indicator showing? You'll need to improvise a way to hold the pinion stationary in order to make an accurate measurement.

Try again, but use a very thin coating of marking compound, and apply resistance to the differential as you turn the yoke, and turn the yoke enough times to rotate the differential several rotations in each direction. Have a helper restrict the differential while you turn the yoke with a socket wrench, then turn the differential while restricting the yoke, doing both it in both directions. Too much compound acts like a lubricant and hides the pattern. Also check the pattern in at least 4 places around the ring gear when you think you have the final setup.

There's always a little runout in the differential flange and the ring gear. The final setup will be a compromise between the best and worst patterns. Same holds for backlash.

Do you have the FSM, or at least the 7.25 axle pages?

How are you spreading the axle housing? It has to be spread 0.012-0.015" in order to insert the differential with the proper preload shims.

Ken
:-)
Author:  RustyRamcharger [ Sat Sep 12, 2009 12:17 pm ]
Post subject: 
I forgot to mention...If you look at the old pinion, there should ne markings stamped or engraved on the face of the gear. Compare it with the new pinion. The FSM has a chart in one of the other axle sections that shows what the shim difference should be between the old and new. Use that as the basis of the new setup. Did you measure the shim(s) from the original pinion setup?

Similarly you can get the approximate setup of the differential preload from the original shim configuration.

Ken
:-)
Author:  dakight [ Sat Sep 12, 2009 12:45 pm ]
Post subject: 
This is the newer style diff with the screw type side adjusters. No shims are used on the differential; only on the pinion.
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