Ring and pinion sets dont interchange!?

[V8_Kind_Of_Guy]

I was always under the impression that all 8.8 factory ring and pinion sets were interchangeable. According to LRS website, FRPP sets are all the same for 86-2010 models. I have a 3.73 set from MotiveGear that I took out of my car and wanting to change to a factory set of 3.27 from a 95 Gt auto. It has the Ford logo stamped it. But when I try to set up the pinion, there is still a lot of slop, about 1/4 inch. What's the deal? Found that the splines are a little shorter on the OEM one, but still. Anybody have any ideas? Heres a pic I took of the 2 side by side.

 

[jrichker]

Did you use a new crush spacer sleeve on the pinion shaft? Every time the pinion gear is removed after being torqued down, the spacer sleeve is supposed to be replaced.

 

[V8_Kind_Of_Guy]

Yes, new crush sleeve, but that'd not even being touched

 

[ratio411]

That's not right at all.
How does your bearing race look???

I wonder if it is possible that you accidentally got the wrong pinion bearing in your set?
Mix ups happen time to time. (EDIT: Nevermind, they look right in the pic.)

 

[ratio411]

When you say "slop", you do mean at the pinion bearings, correct?

I just realized that 'slop' could also mean a loose relation between the ring and pinion gears, which would then be corrected with shims.

 

[V8_Kind_Of_Guy]

The slop is just in the pinion, haven't even out in the ring yet. When I out in the pinion into the housing, put on the driveshaft flange, then tighten the nut on the pinion to drive on the flange, the pinion still moves in and out of the housing about 1/4".

 

[junkyardwarrior]

I assume you mean that when you tighten the nut against the flange, you can move the pinion back & forth a good bit. If that is the case, how tight are you tightening the flange nut? It takes a LOT of torque to crush the crush sleeve. If the sleeve isn't crushed, the bearings are still a good 1/4" apart which causes your slack.

One reason I prefer the solid collar that uses shims to set the pinion bearing preload over a crush sleeve. The crush sleeve is fine but I'm lazy and don't wanna be messing with 300 lb-ft of torque or whatever it is that it takes to crush the crush sleeve while laying on my back under a car.

 

[V8_Kind_Of_Guy]

I've used a 24 inch long rachet to get it tight. When that didn't do it, I put in 150 psi in my 33 gal compressor and used a 1/2" impact that's rated at 810 ft lbs. And yes, you are correct, its the pinion that you can move back and forth.

Any clue?

 

[Maryland Stang]

Okay, I told you before, you can't use the shim thickness from the Motive pinion as the required shim thickness on the FRPP pinion. It will not be the same. You're going to have to do a complete pinion setup. If you were going from FRPP gears to another set of FRPP gears then you should be able to do that. But not when switching gear manufacturers. The Master Housing Dimension setup does not work with non FRPP gears. Since the required shim thickness for the MHD was lost for this rearend when the Motive gears were installed then you'll need to reset it back up.

"The Master Housing Dimension (MHD) is the distance between the axle centerline and the back of the pinion head. (See figure 15) This equals Pinion Head Thickness + Pinion Depth. Since your factory gears were installed using the MHD method from the factory, you know that your pinion depth was properly setup with the correct pinion shim. Since we are changing the pinion, we must now calculate the correct pinion shim thickness. For an example, if Pinion Head Thickness was 1.781 and the shim was .019” thick, doing the math: (4.415-1.781=pinion depth of 2.634) The .019” shim was used to reach that pinion depth of 2.634. If our new pinion head is now 1.770” thick, doing the math: (4.415-1.770=2.645 pinion depth). Since the difference in pinion thickness is .011 less on the new gear, we must ADD .011 to the existing .019 shim to get the correct pinion depth. This leaves us with a .030 shim for the new thinner pinion gear. If the new gear was 1.792, .011” thicker than the old gear, we would subtract .011 from .019 and use a .008” thick pinion shim. Using this method, I have double checked the MHD with my pinion depth checker and found it within .001” of my calculations on both installs. This is the easiest way to do it, and will save a lot of time in installing, measuring, disassembling, and changing shims; not to mention re-installing and measuring all over again. "

SSOTN - Gear Install

 

[V8_Kind_Of_Guy]

I'm starting to understand, but where did the 4.415 come from?

 

[Maryland Stang]

I'm starting to understand, but where did the 4.415 come from?

That is the measurement that the Ford engineers came up with to set the pinion perfectly at the correct depth on the ring gear. Even the slightest changes in literally any part changes the depth. All of Ford's gears are made virtually identical as are the critical measurements inside the rear end housings.

If you can put 2 pinions side by side (like you've done) and see a difference then the 2 pinions will require a different setups to get right.

 

[StinkinLincoln]

i know this thread is very old, but i would like to know the outcome. i traded my fr gears for some jegs brand. my pinion head on the new set is much shorter, just like yours. if i measure the head thickness and use that for the shim basis, i would need a .118 shim! holy crap!
so far i have tried .010 shim, .025 shim (stock), and .063 shim. still no dice on the pattern esp on the drive side.

 

[rd]

Have installed both Ford and Motive gears. The Fords set up with the same shims as the last one, check the pattern and adjust. The Motive I had to do a country boy check of the master pinion depth, guess/calculated a pinion shim and went from there. Took three press on and off trials to get the pinion set close enough to start on the ring gear and preload.

 

[Windsorfox85]

.

 

[Windsorfox85]

The slop is just in the pinion, haven't even out in the ring yet. When I out in the pinion into the housing, put on the driveshaft flange, then tighten the nut on the pinion to drive on the flange, the pinion still moves in and out of the housing about 1/4".