8.5 in rearend

[ssn696]

"This process is excruciating."

I appreciate your efforts to document actual work on this 40- year old hardware. It seems that most advice requests are from those unwilling to invest the time to give back to the Tribe. You're earning your stripes. Thank you.

 

[Built6spdMCSS]

Go back to the .040, check the backlash.

Took me a little bit to get my pattern dialed in good when I did my 9". Some gears set up quick, some take a little bit.

 

[doood]

This is 0.043 shim with 0.008 backlash. I think it is deep.

I'll go back to 0.040 and 8 or 9 backlash since 64nailhead says tight is noisy.

Thanks for feedback Built6spdMCSS

 

[doood]

Factory 0.038 shim from factory 3.73 open diff, 0.008 backlash.

Took prints 180 deg apart. Put a kids belt on the carrier to apply torque to get better contact.

0.038 to 0.040 will do the job. thanks for suffering with me. Posting here helps me keep the prints cataloged; my phone is just full of pics now.

 

[Built6spdMCSS]

Yup tight is definitely noisy. That pattern I'd run that .040 shim and let it rip.

 

[doood]

Final torque with red locktight 30, 50, finally 65 ftlb. During fit-up the bolts were elbow tight. Uniform backlash around the ring indicates flat and true (heated gear, frozen carrier). I had to make a wooden fixture and stuck a padded breaker bar in the access port of the carrier to get proper restraint. A seemingly trivial job that took several hours of noodling with my brain.

In the latest of a string of financial infidelities, I picked up this 12-ton press for $135 (floor model on clearance). That new inner pinion bearing went on so easily. Who am I kidding? That galvanized iron pipe cost me $9. Believe it or not I used the 0.037 shim (factory nominal)... if you look at every mesh pattern I posted, all but the 0.035 and 0.036 are flat on the root (deep).

 

[doood]

Test-fitting the solid spacer I got 12in-lb of spinning torque on pinion at 0.568 (0.018 shim). Tomorrow I'll see what it looks like with less shim. Shooting for 25+ in-lb.


I have a Seville rear disc brake kit from inline tube that I'm not going to install now, because I don't want to replace master cylinder and combination valve I just want to get this 8.5 in the car in March/April. If it's problem free after 500 miles, I'll put the pretty brakes on it.

 

[doood]

With 0.032 shim on the crush sleeve eliminator, I had over 40 inlb of spinning drag. With 0.034 shim, I had 12 inlb of spinning drag, and the eliminator kit was made to increment by 0.002. So rather than sand a thousandth off the sleeve, I grudgingly went for the traditional crush sleeve, and got 20 inlb spinning drag on the first shot. I used the Walmart-brand ugga dugga good for 330-350 ftlb fastening torque. I've got thread sealant on the yoke's spline, red locktight on new nut, grease on yoke washer, RTV on the circumference of the oil seal. I whacked pinion solidly a few times on both ends with a dead blow and a brass drift; spinning drag unchanged. You guys had me crazy worried about this crush sleeve, but it seems 'I crushed it'. Thanks again for all the help. You'd never know I dropped one of the bearings on the cement floor if I didn't tell you.

 

[doood]

Rebuilding control arms was easier than putting new u-joints in the driveshaft. Plan is to install housing w/pinion and control arms (loose bolts) as a unit. That should be pretty low weight without the axles and carrier, and easy enough to locate with the control arms installed. Waiting on a BMR LCA reinforcement brace; I'll get the car jacked up this weekend.

I cannot figure how the UCA suffered so much more corrosion than the LCA (parts from donor car). There was barely any paint on the donor car UCAs. They've lost mass for sure. I may wind up rebuilding the UCA that come out with the 7.5 if they look a lot better. I de-greased, then sprayed down with phosphoric acid, then rinsed, dried, and applied several coats of flat black rustoleum.

 

[bracketchev1221]

There's only a handful of people I would consider experts. I'm not one of them. At least you're not doing a dual crankshaft timing pinion setup on a Fairbanks-Morse 8-1/8 6 cylinder opposed piston diesel engine. Those ring gears were measured in feet. Same type of mesh checking though. Just larger. And no chance of coast side mesh.

I've learned over the years that experts tend to come to a consensus that the pattern on the coast side pattern isn't a major factor. It's the drive side that matters. Obviously, you want the coast side to have good engagement, too, but it's not as critical to be "perfect" on the coast as it is the drive. I've heard and read that in different places. Again, I'm no expert. If it's important to you is all that matters.

It is my opinion that your 0.038 is the "best" of the three as far as engagement. The 0.035 seems way too close to the face, or top of the teeth, for me.

The 0.038 and 0.042 seems to me more the way to go. Although the 0.038 appears acceptable on the drive side, you seem a bit close to the heel on the coast side, but not too deep. I'd lean to the 0.038, personally out of the 3. Probably even try 0.040 and see if that nets you a tad better centering. But, I realize that's a good amount of work jacking around with all that, it's still worth the extra time now to do it, IMO.

Hey I got 4 Fairbanks 12 cylinder engines for the plant generators.