Working on rebuilding the 8 1/4 rear axle in my brother's Duster. The FSM talks about measuring and setting the pinion bearing preload but does not discuss exactly what this is or how to measure it.

My best guess is that I use an inch-pound bar-style torque wrench to measure the drag/torque required to rotate the pinion gear in the housing. Is that correct/accurate?

If so, does anyone have any suggestion, other than a series of adapters, of how to connect a 1/4 inch drive torque wrench to a 1/2 inch drive socket for the pinion nut and still get accurate inch-pound torque readings?


Thanks.

My best guess is that I use an inch-pound bar-style torque wrench to measure the drag/torque required to rotate the pinion gear in the housing. Is that correct/accurate?

If so, does anyone have any suggestion, other than a series of adapters, of how to connect a 1/4 inch drive torque wrench to a 1/2 inch drive socket for the pinion nut and still get accurate inch-pound torque readings?

Yes that is correct.

Ridhard

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Part of Tyrde-Browne Racing

That exactly how you do it you need an inch pound torque wrench that will read single inch pounds most go from 0 to 25 inch pounds.

Brian

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63 Plymouth Valiant Wagon

You use a "beam type" or "dial type" inch-pound torque wrench (not a click type)- I use two socket drive adapters stacked together- a 1/4" TO 3/8" & a 3/8" to 1/2".
(hello, Mr ToolGuy? I need a 1-1/4" socket, yeah, in 1/4" drive. )

If you're setting up a new crush collar on the pinion bearing, the fun part is "sneaking up" on the correct amount of preload. You have near zero rotational torque on the bearing until the collar crushes & actually allows the bearings to contact the races- it can take over 150 ft-lbs on the pinion nut to do this. Once you start to have any significant preload drag, it takes very little additional tightening (degrees of rotation) on the nut before you achieve or exceed your preload spec. If you go too far you have to tear it about & use a new collar.

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63 Valiant Wagon
225 - 4 bbl

Thanks guys! Glad I figured it out. I have the "beam-type" inch pound gauge that goes up to something like 25.

I need to check on the drive size adapters I have and probably buy a couple.

How assembled does the rear axle need to be when I measure the preload? Fully assebled? Just the ring and pinion assembled?

Thanks.

I've hooked up spring scales to a wrench..........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

"How assembled does the rear axle need to be when I measure the preload? Fully assebled? Just the ring and pinion assembled?"

Just pinion, no ring gear.

Richard

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Part of Tyrde-Browne Racing

Thanks!

Reed

I am getting set up to do a re build on an 8.75 center section,
from what I have read - see on you tube

for pinion bearing preload,, that is correct,, just the pinion gear
to get a value for carrier bearing preload,, you would have the entire diff assembled, use the same inch lb checking method, and account for the already obtained pinion gear preload and the effect of the gear torque mutplication.

Did you change out carrier and pinion bearings and races ?
If so,, how did you get the bearing assemblied back on, press em on, or heat ? What about the races?

"I've hooked up spring scales to a wrench.........."
That is exactly what torque is: measure inches (center-to center), apply force measured on your spring scale (fish scale) and do the math (multiply). It doesn't get any simpler than that. My fish scale is a great tool for torques in tight spots. Incidentally, I had a calibration lab check it once just for laughs- It was one pound off at 50 lbs. That's 2% error. You can check your scale by picking up a known weight (bag of flour?) and checking the reading on the scale.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Note that I am working on an 8 1/4, not an 8 3/4. I dont know if you caught that or not.

I have discovered that I don't have the tools required to properly remove the old bearings from the carrier unit, so I am going to be kind of stupid and cross my fingers and assembe the axle using the old bearings that are on the carrier and pinion that I got form the junkyard. If i am lucky, all will be well. If I am not lucky I have a full rebuild kit that I can drop off at the shop I will pay to rebuild the rear axle and install the new bearings and races. Some things are ust beter left to the professionals for have the right tools to do the job.

Yep, saw that you were doing an 8.25,, but I think pinion and carrier bearing install would be about the same as an 8.75, concerning re using, if the races and rollers look good, no piting,,, they are, I saw a different post where you were wanting to pull the pinion, so I thought you were taking the diff apart.

Yes, I am pulling the pinion. On the 8 1/4, the pinion gear is pressed into the snout of the center of the axle housing and held in place with the pinion nut in the u-joint yoke. Only the ring gear comes out with the carrier. The carrier drops out the back of the housing leaving the pinion in the front.

I am switching carriers as well as ring and pinion gears, so I am going to chance not disasembling the used carrier I am installing. If it works, cool beans. If it doesn't, I have all the parts to rebuild it to give to the shop that will rebuild it for me.

Until they rebuild it twice, it howls worse than before they started, and you're out $800... I'll be spending the money on the tools to do it myself next time.

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