I've been thinking about replacing the diff in my '08 due to a persintant whining noise. its between 40 - 50 MPH (LOUD at 45MPH cruise) and part throttle. silent all other times
unfortunately, the only ones i seem to be able to get are AP1 diffs. while these are the same housing and driveshafts, the input flange uses different size bolts. so you need to swap the flanges.

so if i'm following this right, the process would be

remove large input centre nuts

use puller to remove both flanges

swap flanges, use new nut to pull down flange onto shaft, torque to spec

use inch pound guage to check turning torque, adjust torque of input nut to get in spec

mount diff and drive

anyone done this before? i know the diff requires quite a bit of gear mesh / backlash setup and there's no point doing this if pulling the input flange will change this and require the whole setup to be done again

 

It might be easier to change the driveshaft CV joint to AP1 and use the M8 AP1 bolts.

I generally use bellmetric or Honda for bolts. Aftermarket bolts are class 12.9...which, unfortunately means they can't safely be zinc plated. So hopefully you don't drive in salt if you go aftermaket bolts.

The AP2 diff housing is stronger, BTW. But yes...external form factor is exactly the same.

Have you tried just changing the fluid in your current diff? Or checking its backlash?

 

Yes, I have changed the diff oil twice now. once when i got the car with 75/140 transmax limited slip oil, which i did 5K on, then again with a generic GL5 80 / 90 gear oil, which has now done around 2k. noise has been the same throughout. no noticable metal in the oil, apart from a medium amount of paste on the magnet, which i assume is normal.

as for checking the backlash, is there a way to do that on the car, or is it a diff out job? i seem to recall the back cover is bolted to the car too.

 

The diff would need to be removed and the case opened up.

At that point, may as well replace bearings and seals

All the same stuff you'll need to do if you un-do that flange nut to change the flange, BTW.

 

Pretty in-depth view of what you'd have to do once the diff is off the car. They don't seem to use a guage to check backlash but if you look up PuddyMod's videos he does (Guage is like $40 on amazon).
If you're only checking the backlash then it seems doable and if it's off then you can just bring it to a shop to do a rebuild, etc.

 

I's try one more differential oil change.

The spec for SAE 90 GL5 hypoid gear changed after our cars were built. What's sold as SAE 90 these days is the thinner half of the old spec, the thicker half was spun off to SAE 110. Try a multigrade SAE 90-140 or something similar. Appears this might not work but for $30 why not?

-- Chuck

 

He already tried 75W140, according to his previous post.

 

cheers for the info guys, seems the best option for me would be to get a propshaft from an ap1 and swap the rear flanges (thanks B), then swap the diffs as a unit.

new bolts from honda would probably be a wise purchase too, in my experience old capheads dont like being disturbed.