7.5 Axle Pinion Flange Swap/PCD??

Robintett · Oct 23, 2018

Hi everyone!

I have an 89 2.9 manual ranger.

I recently swapped a used 7.5 rear axle into my truck as my differential had blown up on me. The problem I now have is the pinion flange on the new differential has a larger bolt PCD than that of my previous - so my driveshaft will not bolt up.

The question i have is - can i swap the pinion flange from my previous diff onto the new used one i have fitted? I also know this has to be done properly. Im happy to but a torque wrench as i want one in my tool set anyway but isit just as simple as setting it to torque?

I realise another option would be to get a yoke that fits this correct pinion flange PCD and fit that to my driveshaft? But i worry that may unbalance my shaft.

Let me know if you have any questions if that wasnt clear. Any help appreciated,

Thanks Robin.

adsm08 · Oct 23, 2018

Swapping the flange is 100% doable, and certainly the preferred repair here. A torque wrench would be the right way to go about it, but I don't know the specs off the top of my head. A drag meter is also a good thing to have when doing this job, if you really want to go by the numbers.

Robintett · Oct 23, 2018

adsm08 said:
Swapping the flange is 100% doable, and certainly the preferred repair here. A torque wrench would be the right way to go about it, but I don't know the specs off the top of my head. A drag meter is also a good thing to have when doing this job, if you really want to go by the numbers.

Yes after having a further look into it, it seems that's more what I need, a drag meter rather than a torque wrench. Are you for sure the pinion flanges are compatible? I will attach pics as I thought they looked a little different.

Robin

adsm08 · Oct 23, 2018

They should be. The pinion gear didn't change just the flange. It was upsized to match the bolt pattern of the 8.8 in the early 90s.

Robintett · Oct 23, 2018

adsm08 said:
They should be. The pinion gear didn't change just the flange. It was upsized to match the bolt pattern of the 8.8 in the early 90s.

Thank you. While have your attention, do you know what size the nut is? None of my sockets were big enough when i tried.

Robin

adsm08 · Oct 23, 2018

Not off the top of my head. I am thinking 1-1/16 or 1-1/8, but I am not sure.

I do know you pretty much have to have a chrome socket, rather than an impact.

4x4junkie · Nov 1, 2018

It should be one of: 1-1/16", 1-1/8", or 30mm. I've seen all three at some point on RBVs, though I can't remember where each one was (front or rear), or if maybe one was the t-case flange. The rear pinion flange nut I recall is exposed enough for you to get a regular wrench onto it just to see what size fits.

Yes, only standard sockets will fit (impact sockets are too thick).

I've also seen the large-bolt-pattern pinion flanges like you got redrilled &tapped to fit the smaller bolt pattern, which is not something difficult to do at home since the driveshaft flange is centered by the center bore pilot, not the bolts themselves.

Replacing the flange on the driveshaft should not unbalance it (or at least I have not run into any issues after replacing a few of them myself due to damage from rocks or other reasons). However I don't think it's all that costly to have a shaft balanced, maybe $50 I'm guessing?

holyford86 · Nov 3, 2018

I've always used a 0-75 in-lb dial indicating torque wrench for this kind of work, they are expensive though so you might be able to get by with a beam type wrench if you're in a pinch. The pinion flange doesn't have a set torque as it uses a crush sleeve for pinion bearing preload. the way I do this is I will remove the wheels and brake drums and check my preload in both directions a couple times and write it down for later use. then I would pull the nut, pull the flange, might as well replace the pinion seal while you're there, then reassemble, (preferably with a new nut, but if one isn't available I've used red loctite) I will tighten a little bit at a time until I get to the torque I had beforehand (plus about 2 or 3 inch pounds if a new seal was installed) I have also found that sometimes giving the pinion flange a couple whacks with a RUBBER mallet sometimes will square up the outer bearing. If you do this and the torque value remains the same you are golden and you can reassemble everything else.

kimcrwbr1 · Nov 3, 2018

Do they make a U joint with the two different cap sizes? I cant remember if it was a old ford or mopar i did that once or maybe is was a corn binder (amc bastard) Scout I used to own?

7.5 Axle Pinion Flange Swap/PCD??

Robintett

New Member

adsm08

Senior Master Grease Monkey

Robintett

New Member

adsm08

Senior Master Grease Monkey

Robintett

New Member

adsm08

Senior Master Grease Monkey

4x4junkie

Forum Staff Member

holyford86

Some guy with a problem

kimcrwbr1

Well-Known Member

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