Rear Axle: 10 Spline to 24 Spline Conversion / Seal Refresh / Ashcroft Locker Install - Page 2 - Defender Source
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  #21  
Old February 1st, 2015, 01:03 PM
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Spent 4 4 hours days at chez galpin (ok, plus another day to unload my galvy and another day to clean everything up) pretty much making a fool of myself rebuilding and installing the diff. It took me probably 22-24 hours to do this job, because I had no idea what I was doing until the very end. I could probably do it now in half the time.

Many thanks to my host for letting me leave my junk there and use his garage!

As measured with a Park in-lb beam torque wrench:
25 in-lbs pinion only preload
35 in-lbs pinion preload with diff (translating to 35.4 in-lbs preload on diff, if I calculated correctly)

Crown gear installed on Ashcroft diff with red loc-tite and torqued to spec, used new 10x3/8"-24x1" long grade-8 shoulder bolts.

Runout on the crown gear was within spec (<= 0.004")

Replaced one carrier cap bolt with the included bolt from Ashcroft to mount the key. Used blue loc-tite on carrier cap bolts after thoroughly cleaning internal threads and torqued to 55 ft-lbs.

When I pulled the pinion from the diff, the original setup had a single 0.030" pinion shim.

In order to get a good pattern after installing , I had to re-shim the pinion gear to 0.213" (???) I went all the way down to 0.008" and all the way up to 0.223".

I didn't pattern my crown gear with the original diff but I imagine that at 0.030" the original mesh wasn't all that great!

Installed new bearings all around (pinion and carrier)

Measured backlash at between 0.004" and 0.007" as per spec, although a few teeth were at 0.008". I went with this because the pattern was better with this backlash and I felt more comfortable with that than running 0.003" to 0.006" with a max at 0.007".

The brass air fitting on the Ashcroft on my diff pointed sideways at the crown gear instead of down and parallel to the crown gear. I added some curves to my copper pipe as strain relief, and blue-loctited the fittings so they wouldn't come loose in the diff.

Drilling the third member is incredibly easy. I'm not sure what material it's made of, but it's incredibly soft - almost like cast iron.

I tested the locker using a QD test fitting and got it to engage at around 65-70psi. Without the locker engaged, the halfshafts can be spun independently and rotate in reverse directions. With the locker engaged, the halfshafts can only be turned by rotating the pinion, and rotating the pinion results in both halfshafts rotating the same direction.

I think I'm going to run a pressure regulator with my solenoid, because I don't think these solenoids are actually made to operate at 150psi, which is what my OBA charges the tank to.
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  #22  
Old February 1st, 2015, 01:16 PM
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btw, the Ashcroft install manual says the fitting on the third should be drilled and tapped to 1/4" bspf. This is the same as 1/4" NPT, the tap can be found at any home depot store.

------ Follow up post added February 1st, 2015 01:20 PM ------

Also, for anyone who plans to set up their own diff in the future, here's the best procedure I can recommend after doing this myself:

0. Take a picture of the current wear pattern on the crown gear
1. Mark original bearing caps with housing to make sure you keep the left on the left and the right on the right (I made two shallow marks with a drill bit on the left side and one shallow mark with another drill bit on the right side.)
2. Remove the adjuster locking lugs by tapping out the pins
3. Remove the bearing caps and threaded adjusters.
4. Remove the diff assembly.
5. Remove the pinion nut with an impact wrench.
6. Pull off the washer, pinion flange, spacer, upper bearing, and remove pinion from third.
7. Remove outer and inner pinion bearing races using a hammer and punch.
8. Remove the inner pinion bearing with a puller. I did this using galpin's press and the jaws from my bearing puller kit. There's not a whole lot of space between the bearing and the pinion.
9. Discard old outer and inner pinion bearings and the outer race. Do NOT discard the inner race! (the larger diameter race)
10. Using a grinder or other tool, reduce the diameter of the used/original inner race by a few thousandths of an inch.
11. Thoroughly clean all surfaces with brake cleaner and paper towel. compressed air wouldn't hurt either. You do not want any dirt or particles on the bearing race surfaces otherwise they will screw up your measurements.
12. Press in the new outer (smaller race) into the third member.
13. Press the new inner bearing onto the pinion.
14. Now you can set the pinion spacer easily by using the original inner race (which you have ground down) and all the other new bearings/races. This allows you to easily swap out pinion shims without having to press out the inner race.
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  #23  
Old February 1st, 2015, 01:38 PM
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0. Take a picture of the current wear pattern on the crown gear

Nicely done. I should have turned the garage cam on and we'd have enough footage for a season of "one man, one diff..."
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  #24  
Old February 1st, 2015, 01:49 PM
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Thanks Charles! I edited my post to add step zero
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  #25  
Old February 3rd, 2015, 07:39 AM
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stubs and hubs from a donor Disco I (abs as you can see). mud shields as well.

derusted in phosphoric acid, used a cup brush to clean up the rest to bare metal, sprayed a light coating of paint on non-critical surfaces to prevent future rust (did the same on the front of my truck and it works well.) A little messy on the masking, but I guess the brake pads will clean that off.

new rotors.

Also remember to keep the halfshaft flange screws from the donor truck since the old ones from the 10-spline flanges won't thread into the 24-spline hub.
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  #26  
Old February 3rd, 2015, 11:02 AM
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jefhuf reminded me that there is a difference between the 1/4" BSP and NPT threads - 19 vs 18 tpi and a different tooth included angle.

I don't anticipate an issue with the tapered BSP fitting in an NPT hole for the sake of plugging the differential, but if I do run into any problems, I will re-tap with BSP.
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  #27  
Old February 6th, 2015, 04:25 PM
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ordered a pair of new pinion flanges and dust shields. Quite a groove worn into the old flange.
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  #28  
Old February 6th, 2015, 04:44 PM
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yikes, don't wanna know how much those were. Ever heard of a speedi sleeve?


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ordered a pair of new pinion flanges and dust shields. Quite a groove worn into the old flange.
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  #29  
Old February 6th, 2015, 04:51 PM
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Quote:
Originally Posted by Ren Ching View Post
yikes, don't wanna know how much those were. Ever heard of a speedi sleeve?
$15 from Craddocks...is that under/overpriced?

I had to get a replacement 200tdi dipstick from them so I bought the flanges as well. Nobody had a new 200tdi dipstick here in the states, unfortunately...
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  #30  
Old February 6th, 2015, 04:55 PM
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wow, that's not bad! I priced them for my series truck awhile back and it was alot higher. but that was from a stateside vendor.

PS, I said I didn't wanna know
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  #31  
Old February 6th, 2015, 05:58 PM
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PS, I said I didn't wanna know
Crap! Sorry
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  #32  
Old February 6th, 2015, 11:54 PM
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Quote:
Originally Posted by sonoronos View Post
jefhuf reminded me that there is a difference between the 1/4" BSP and NPT threads - 19 vs 18 tpi and a different tooth included angle.

I don't anticipate an issue with the tapered BSP fitting in an NPT hole for the sake of plugging the differential, but if I do run into any problems, I will re-tap with BSP.
Probably too late, but I bought a tap to do my diff a few years ago you are welcome to borrow. I remember it not being cheap for the one-time-use plan I had for it...
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  #33  
Old February 8th, 2015, 11:38 PM
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Thanks Loic - I will ask to borrow it if gear oil isn't kept in the diff...it really doesn't seem to make a big difference (based on my experience with 1/8" NPT vs BSP taper fittings), but I've been known to be wrong in the past for sure.

Just some pictures.

1. Old / new setup (before work / after work). I haven't bolted the halfshafts in as I haven't installed the diff yet, so that's why it's sort of left hanging in that pic.
2. A picture showing the difference between the stub axle of the RRC vs the Disco I.
3. A picture showing the difference between the lock nut washer of the RRC vs the Disco I. The Disco I's lock nut washer is quite different from the RRC's. The RRC washer is much thicker, smaller in outer diameter, and also has a rubber seal built into it.
4. A picture showing the difference between the hub where the halfshaft flange bolts into the RRC vs the Disco I. The RRC surface "sticks up" more and has some tapers machined on the outside to match the shape of the mushroom halfshaft flanges. I guess the 10 spline is called "Imperial" and the 24 spline is called "Metric" although I have no idea what the terms are referring to: bolt spacing? thread pitch?
4. Just for fun, a picture through the axle housing. Don't mind the dust...I cleaned it out before I did the actual work.

Also, the mud shield of the Disco 1 has a rubber lip seal that protects the inside of the brake rotor. The mud shield of the RRC leaves a lot of space between the shield and the rotor and so it was no surprise to find a lot of dirt and mud caked in there.

I did not re-install the ABS reluctor rings as I don't have ABS.

I never touched the rear hubs/stubs when I did my rebuild, so it was really satisfying to clean everything up
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  #34  
Old February 8th, 2015, 11:51 PM
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I removed the inner stub seals and plan to run my hubs wet. My original 10 spline hubs were wet and I was pleased with how little wear was on the old bearings.

Also, in the past, I have used Mobil 1 Synthetic Grease (Red) in my truck. I switched this time to Green Grease and I was pleased to find it pack more easily into the bearings and also to be significantly "stringier" in consistency.

------ Follow up post added February 8th, 2015 11:56 PM ------

Also, as another note, if I wasn't planning on rebuilding my entire rear, it would have cost only about $250 more to purchase Ashcroft's "Early" HD 24-spline axles, which are a drop-in fit for the 10-spline RRC hubs. I would then have to buy HD flanges as well ($100+) but I would have ended up with an HD rear.

Something to think about if you are planning this conversion yourself...
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  #35  
Old February 10th, 2015, 04:53 PM
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wow , great job for a newbie my friend.
fyi and if you think you can use it in the future, I have a fine spline matched factory ratio (3.54) ring and pinion, installed but not used (ran a from inside the shop to outside and then in again for locker and lower ratio install) from a past project...
I don't have a yoke.
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  #36  
Old February 14th, 2015, 12:05 PM
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progress is slow due to the cold, but I finally have everything bolted up and the air line running to the engine bay. New grade 8 nuts and bolts everywhere.

Not sure yet where to put the regulator and solenoid.

I've attached a video of testing the locker. Seems like it works ok with no air leaks.
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  #37  
Old February 14th, 2015, 07:09 PM
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Filled the diff with Mobile 1 synthetic 75W90 for break-in.
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  #38  
Old February 16th, 2015, 10:20 AM
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Good work Kang!
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  #39  
Old February 27th, 2015, 02:56 PM
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Thanks Jeff and Carlos!

I drove the truck a bit today and as an added benefit, the horrible grinding / "graunching" noise on deceleration is totally gone. It's difficult to describe how horrible this noise was before I did the work. Now the truck doesn't sound like it's destroying itself every time I let go of the accelerator pedal.

Not exactly sure what the fix was, but it was almost definitely changing the pinion bearings, re-setting the diff crown gear contact pattern, and setting the correct pinion and diff preload.

I can't wait to test out the locker on some terrain....
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  #40  
Old February 27th, 2015, 04:01 PM
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Designed a switch panel flange for the locker switches. The front locker switch is a dummy Carling switch.

Ed, Is that from a 3d printer? Care to share?

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