65 i6 7.25 inch rearend help
 

Im helping with a 65 i6 with the 7.25 rearend. This car makes an awful din from the back as you drive its quite noisy despite being quite everywhere else. I suspected that it was rearend bearings particularly the axle.

We pulled the axles and one bearing was good one was starting to fail.

The axles were covered in what looked like thinned down tar.

Pull the back pate and there was a few cups of thinned down tar that dripped out. I guess thats what happens to gear oil after 50 years it wants to revert back to crude oil.

Pull the bearing caps and removed the center (diff) out so that it could have new bearings placed on it as well... The bearings and gear oil look original.

The gear teeth look to be in good to excellent shape

I need help figuring out how to replace the bearing caps so they properly compress the outer race they have threads cut in both haves of the bearing carrier and a threaded disc that can at least slide into those threads...but maybe able to screw in if both halves were assembled?? I dont know how this is suppose to work but I can tell that its important for properly compressing the bearing race right?

One side fell apart as I pulled the diff out but the side pictured remained together and is set exactly as the factory had it...do I just match the other side and stick it back together...or is there a better way?

Also how much gear oil does it take? Do you just pour it in from the axle bore once the back plate is on until it drips out the axle?

Thanks

-Gun


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That type of axle Ford called an Integral Carrier Axle, meaning the center section did not have a removable gear carrier separate from the housing. It is VITALLY important that the adjusters which preload the differential carrier bearings are not only properly set for preload, but ALSO for establishing the proper gear "backlash", tooth clearance.


I can scan and post the entire repair process with diagrams for you right out of the Ford original Shop Manual, if you can wait until tomorrow. Many a set of gears has been ruined by improper setting of those adjusters. If I'm too late with this, please let me know, as scanning and then uploading to image processor is pretty time-intensive. Thanks. imp

Actually dude I just bough the ford service manual E version for the exact reasons you stated. (which I dont recommend unless you need it straight away its burden with software that makes it mostly useless. )

This 7" business is a bummer because I cant just take the center to the shop and be like "fix this POS" like with the 8 or 9 inch.

My question is now is that it appears this system uses non-hunting gears which require them to be matched back up to the timing marks...How ****ed am I if I cant find those marks?

Is this the section that your service manual also shows?

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Pretty much. It shows a tool used to rotate the adjustment nuts, but without that tool, you can use a blunt narrow flat chisel and light hammer. The big bearing cap bolts, if tightened to spec, sometimes clamp the threads and make it near impossible to turn the adjusters. I usually go to about 10 or 20 ft. lbs., to make everything nice and straight, and then tighten as necessary to obtain correct lash, then check tooth contact pattern. Drive side is more important than coast, if compromise must be made in order to get reasonable lash. If you haven't disturbed the pinion location, it will be easier to get good diff. brng. preload and lash. Most Ford manuals called for snug plus 2 to 2-1/2 holes tight. Look for that spec. or an actual preload called out in in.-lbs. But, to check preload torque, the pinion must be removed. Easy on the 9" or 8-1/2", with the separable pinion retainer with 5 bolts.


If you know what non-hunting refers to, I'm probably being too explanatory for you, no negatory intended. The non-hunting sets usually have 2 paint dabs on the ring gear, which sit beside 1 dab on the correct pinion male tooth. I've always heard incorrect indexing on a non-hunter will produce hum, never tried it. Can't imagine it causing failure. How do you know it's a non-hunter? Number of teeth would have to be exactly divided, like 30 and 10, exactly 3.00. Same tooth on pinion engages same hole on ring every time ring makes a turn. Nice talking with someone who has followed these things, can talk knowledgeably. I'd bet less than 1 out of 1000 members would know what non-hunting means! imp

I am not 100% sure that is isnt a hunting setup. I can try locate the tag to verify.

Butttt.... this service manual shows NO 7.25 manufactured as strictly hunting (see part 4-3 specifications in service manual). They are all listed as strictly non-hunting or partial non-hunting and both those types indicated they must be timed...This sound quite easy based on the description you gave and the service manual. the single dot on the pinion fits between the two dots on the ring gear so you have 3 dots in a row....The issue is going to be trying to find those dots... maybe.

I have not pulled the pinion gear so I should only have to deal with backlash not depth.

I plan to weld up a simple tool using flat stock and some dowel.

Between the one bad axle bearing and the 2 cups of tar that fell out it should run a lot quieter with fresh oil and 4 out of 5 bearings bran new. Despite this it did not wine it made a loud low frequency drone... Imagine a smooth growl.

The pinion bearing feels tight and smooth with no play vertical or horizontal. The diff bearings did not look awful so im hoping the pinion would look the same...at least it feels fine.

Regarding that pinion: You have not removed the U-joint yoke? Turn the pinion with your hand, feel for a slight drag, not much, but still, resistance to turning. This is important, if the pinion is able to wiggle around, even imperceptibly a few thousandths of an inch, it will be lunchtime for the gears. Note smoothness, also, roughness indicates pinion bearing replacement is mandatory. Good luck! imp

I didnt touch anything on the pinion side.
That's a good idea I'll drop the DS and check to see that is still has the proper pre-load and check again for play.

Book says something like 26" pounds. so yeah just a bit of drag.

Well got it back together and it runs very well, super smooth and quite on drive and coast side.

I went for largest tolerable level of backlash between 11 to 13 thou book calls for between 8 to 12 thou.
I went for highest amount of pre-load at 3 notches past contact. book calls for 2 to 3 notches.

Checked backlash like 4 times and each time I had the tool setup proper I got consistent readings.

Pulled the Drive shaft and checked for resistance....yes the pinion still has noticeable drag, feels pretty smooth (not noticeably worse than the new bearings) and no play can be felt or heard.

checked coast and drive contact and I guess its alright **** I dont know it kind of matches the patterns in the book but there isnt anything I can do about them anyhow without screwing up backlash and I never touched the pinion.

Found the paint marks and lined them up.

hope it stays fixed. It sure is a hell of a lot better sounding.

Thanks

-Gun

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I guess im all about that life now...