Pinion Flange Removal/Install

dubster99 · Mar 31, 2018

I purchased a used complete 3.31 diff to swap into my 3.73 car. After getting everything installed, I went to bolt the driveshaft up...and found out it wouldn’t mate with the pinion flange. Somehow the diff came with an auto flange. I’m going to purchase a new manual flange, nut, and seal. If I’m just pulling one flange and replacing it with another, will the crush sleeve also need to be replaced? How much of a bitch is this process?

Anthony 05 GT · Apr 1, 2018

Yes, you should get a new crush sleeve. The pinion bearing preload should also be properly set. If you were just swapping seals you could re-assemble everything after marking the nut to pinion shaft location and tighten it to the same marks keeping the crush sleeve intact the same as it was.

Since you are installing a different flange the preload should be set according to factory specs. Normally the preload is checked without the ring gear in place meaning only the pinion shaft and bearings attached. I use an old style pointer inch lb torque wrench to rotate the pinion by the nut and watching the pointer on the torque wrench for the proper preload. If the pointer shows too little inch lb resistance that tells me to tighten the nut more to reach the proper resistance when it comes to bearing preload.

Some techs may tell you a different approach, but doing it according the service manual is always your best bet. You don't want the bearing preload too tight or too loose for obvious reasons...noise or bearing failure.

JohnVallo · Apr 1, 2018

Pinion Flange Swap

dubster99 said:
I purchased a used complete 3.31 diff to swap into my 3.73 car. After getting everything installed, I went to bolt the driveshaft up...and found out it wouldn’t mate with the pinion flange. Somehow the diff came with an auto flange. I’m going to purchase a new manual flange, nut, and seal. If I’m just pulling one flange and replacing it with another, will the crush sleeve also need to be replaced? How much of a bitch is this process?

I’ve done a few of the Super 8.8 rear ends and can tell you it is a lot harder to do the pinion swap in the car rather than outside the car. Having said that you will need a couple of specialty tools (pinion flange holder, and puller). The pinion flange is a rather tight fit on the pinion splines, I haven’t had one yet that I didn’t have to use a puller to remove it. (Never hammer on the pinion flange to remove it!).
The crush sleeve question:
Is the new collapsible spacer recommended? YES
To do it right? YES
Would I do the job without a new crush sleeve? PROBABLY NOT
Having said that, Has it been done successfully without one before? YES
Here’s the risk: Trying to use the old crush sleeve means you would have to get the new pinion nut torqued just tight enough where it wouldn’t collapse the old spacer any further. If the spacer gets collapsed any further, the pinion bearings are too tight, run too hot, and you will burn them up. When the spacer gets collapsed too far you have to remove the differential, and pinion shaft from the housing to replace the crush sleeve. The crush sleeve won't clear the outer pinion bearing cup in the housing so you can't remove the crush sleeve from the front, you have to remove the pinion shaft from the housing .
I have played around with this somewhat and can tell you you would only get about 75-100 ft pounds (safely) of torque on the pinion nut without collapsing it further.
If you want the Official FORD Instructions, Here they are:
https://performanceparts.ford.com/do...M-4851-M8A.pdf

tom_sprecher · Apr 1, 2018

Anthony 05 GT said:
Yes, you should get a new crush sleeve. The pinion bearing preload should also be properly set. If you were just swapping seals you could re-assemble everything after marking the nut to pinion shaft location and tighten it to the same marks keeping the crush sleeve intact the same as it was.

Since you are installing a different flange the preload should be set according to factory specs. Normally the preload is checked without the ring gear in place meaning only the pinion shaft and bearings attached. I use an old style pointer inch lb torque wrench to rotate the pinion by the nut and watching the pointer on the torque wrench for the proper preload. If the pointer shows too little inch lb resistance that tells me to tighten the nut more to reach the proper resistance when it comes to bearing preload.

Some techs may tell you a different approach, but doing it according the service manual is always your best bet. You don't want the bearing preload too tight or too loose for obvious reasons...noise or bearing failure.

I have done several rear ends and this ^^^ is how you do it right. Except you need an inch ounce beam style torque wrench.

dubster99 · Apr 1, 2018

Thanks for the heads up guys. Sounds like a fun job. Lol

dubster99 · Apr 1, 2018

Is there any reason why I couldn’t remove the nut with the parking brake on?

Anthony 05 GT · Apr 1, 2018

Those nuts can be so damn tight that the cheesy parking brakes won't hold. I usually use a 3/4'' impact for removal only.

tom_sprecher · Apr 1, 2018

The pinion nut is on there with over 300 ft lbs of torque. You will need to make a tool that bolts to the flange, still gives access to the pinion nut and is about 2 feet long. Then you need a breaker bar with a pipe to extent the length. Otherwise you will not have the leverage needed to tighten the nut enough to crush the sleeve and give the required pre-load.

kcc0521 · Apr 1, 2018

tom_sprecher said:
The pinion nut is on there with over 300 ft lbs of torque. You will need to make a tool that bolts to the flange, still gives access to the pinion nut and is about 2 feet long. Then you need a breaker bar with a pipe to extent the length. Otherwise you will not have the leverage needed to tighten the nut enough to crush the sleeve and give the required pre-load.

It may take 300 ft/lbs to crush the sleeve but it is not that tight. I changed mine out when I switched to an auto. I used a steering wheel puller to remove the flange after I got nut off. Have someone hold the brakes There are ford instructions out there on how to change it without upsetting preload.

kcc0521 · Apr 1, 2018

https://www.cjponyparts.com/skin/frontend/cj-pony/default/images/install-pdf/install_m4851m8a.pdf

dubster99 · Apr 1, 2018

That nut sounds fun to get off. I don’t have air, doubt my electric impact is strong enough, and the car is on jack stands. I should’ve checked the damn flange when I got the diff but figured a manual diff would have a manual flange.

GTBOB · Apr 2, 2018

What is the actual difference between a manual pinion flange vs. the auto?

dubster99 · Apr 2, 2018

The tabs around the flange go almost all the way around on the manual version. Also some of the chamfered edges and such on the manual version aren’t there on the auto. It won’t let the driveshaft seat properly to get the bolts in. I may see if I can remove more material and get it to go.

MikeyPee · Apr 2, 2018

Ehhhh. Just fulfill your GM fantasy and trade her in

dubster99 · Apr 3, 2018

MikeyPee said:
Ehhhh. Just fulfill your GM fantasy and trade her in

F yo couch Charlie murphy

Pinion Flange Removal/Install

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