Axles

Oldiron440

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There should be a vent hose that goes up the body, sometimes it gets left off or there is a cap with vent holes on the axle and sometimes that's missing this will allow water in the diff.
 

MoparDan

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The whole thing was under water during the hurricane, even the interior was soaked I'm not sure how long but it was aleast a few hours
 

MoparDan

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I went though my service records and heres what I could find about the differential:

May 5, 2015: new pinion bearing and seal, 165,008 miles

June 2, 2015: all new bearings and seals, 168,283 miles (though I think I recall there was one bearing that either we couldn't find, or was out of stock)

December 6, 2017: new fluid, cleaned cover and hardwear, 190,322 miles (this was after it was under water during the hurricane)

December 12, 2018: added fluid, 195,447 miles

I know the fuild was changed a few times before any of this, and I believe the axle seals were replaced sometime in 2012, unfortunately all my service records before May 4 ,2015 were destroyed in a hotel fire this past July...
 

Duke5A

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The U-joints were done some time in 2014 so they're not super old, is there a way to check them?

Get under the car and grab the driveshaft with both hands and push up and down - you're looking for play. Do this at both ends.

Bad u-joints typically howl the clunk when you put your foot into the gas pedal.
 

Miradaman

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I would just find a replacement axle at the nearest salvage yard. I had to swap out several in my old Miranda. The first one the spider gears went bad. I bought a junkyard 8 1/4 for $75 and just bolted it in. Later I changed to a Sure Grip 2.94 out of a cop car. Pretty easy to change.
 

BudW

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A bit late to the story.

To determine if you have a 7¼” or 8¼” – look at the axle tubes where they go into the center housing and look at the inspection cover.

The differential tube size (the tubes that goes into the center housing) is 2½” diameter for 7¼” differentials – which is the size of all 7¼” differentials (from ’60 to early ‘90’s). Now with that said, somewhere in the late ‘70’s, Chrysler changed the tube diameter on 7¼” differentials to 3” – but they have a distinct taper down just before the center housing. That way the ISO-clamp system can use either 7¼” or 8¼” differentials. The early F & M bodies with 7¼” use a different ISO-clamp because of the tube diameter has different spacing – but I doubt there are many of those 7¼” differentials left out there to worry about.

The tube measurements are outside measurements – even though it is hard to tell by my crude picture(s).
7.25 Diff Identification.png

7.25 Cover Gasket.PNG

The 7¼” cover is shaped like a stop sign (octagon) and 8¼” is oval shaped.

8.25 Diff Identification.png

8.25 Cover Gasket.PNG


All 8¼” covers have 10 bolts.
Some 7¼” covers have 9 bolts and some have 10 bolts (not sure when that change was made).

I have a few pictures of a 7¼” – but couldn’t find them, so I drew a rough sketch to demonstrate what to look for. The 7¼” is the ONLY differential Chrysler made with a step-down tube.
The only thing that will interchange between the two differentials is the yoke and brake backing plates (well, all brakes parts). Nothing else will interchange.

If you currently have a 7¼”, I would recommend finding an 8¼” (or 8¾”) and have it under the workbench until existing differential finally gives up. I have, what I feel, is the easiest procedure to change differentials in a garage (or parking lot) – if you don’t have access to a lift. Just perform a keyword search with my user name.


If replacing a 7¼” and 8¼” - the propeller shaft length will be a bit shorter (and shorter still with the 8¾”). Other than that, the two differentials will interchange without problems (. . . well, unless you have one of the very few early F/M bodies with the 2½” tube 7¼”, in which you will need ISO clamps, as well – or better yet, get rid of the ISO-clamp system altogether).



Anytime I’m working on a suspected differential noise concern, I would first get car jacked up (fairly high) and jack stands safely in place. Not necessarily in this order – but check all these items (with park brake off and transmission in any position other than park):
- At each wheel, grab tire at 3 and 9 o’clock, and push in/pull out on wheel. You should notice a very slight amount of play, only.
- Same hand position push one hand in/pull one hand out, then reverse (checking for wheel bearing play). You should notice a very slight amount of play (only).
- Move hands to 6 and 12 o’clock position and do same thing. Most wheel bearing problems will be noticed at this time.
- With a hand on tire always, rotate tire and listen to anything unusual (like bearing or scraping noise).
- Quickly start and stop tire rotation. You will feel more play, but it should only be a minimal amount.
- Repeat these steps on other side rear tire.
- Get under mid-position of car. Grab ahold of propeller shaft at front U-joint area and other hand on front yoke (if possible). Keep the hand on yoke still while using other hand to move the propeller shaft up/down and check for any play (non-should be present).
- Do same thing but this time trying to move propeller shaft side to side. Again, no play should be present. Note: there might be some play between front yoke and transmission – which I see a lot. There shouldn’t be any play there, but it happens. That is a bigger job to fix, than U-joints are.
- Spin propeller shaft (having a helper does wonders in this case) and check for any obvious kinks, dings, dents, bends, twists, etc. in the propeller shaft (none should be present).
- Go to rear U-joint and check for up/down and side/side as above, while keeping another hand on rear yoke (if possible). No play should be present in either U-joint or with yoke.
- Using both hands, move propeller shaft fore/aft – looking for any change with rear yoke and differential housing (non-should exist).
- Check the rear yoke nut is in place and appears to be tight. If that nut gets loose - it will cause a lot of clunks and other noises.
- Rotate the propeller shaft while feeling for/listening for any bearing noise (nothing should be detectible).

The pinion seal should not leak – but it is not uncommon for them to do so on higher mileage cars. Generally, when it does leak – it is more because of bearings are loose/not adjusted correctly than a seal failure. The seal just can’t compensate when bearing allows shaft to move all over the place.

If you have a leaking seal (leaking to a drip) – KEEP AN EYE ON OIL LEVEL!
Wait, did I shout that? No, well let me say it much louder this time: If you have a leaking pinion seal (leaking to a drip) – KEEP AN EYE ON OIL LEVEL!
Your leak will only get larger and there is not much lube in those differentials to begin with (about 2.2 pints of lube). Lose enough lube and you WILL BE stuck somewhere, digging out your tennis shoes out and getting ready to to start walking.


I’ve worked on a lot of flood vehicles, before. The important part is to keep travel to a very minimum and change fluids out as soon as possible. A trace bit of water left in a differential will not be a problem – for differentials get rather hot when in use, and any evaporated water will exit via the vent - in a short amount of time.

A couple tablespoons full of water (or more) will, I repeat, will wreak havoc on your differential bearings, in a short bit of time.
 

MoparDan

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The day before yesterday went to have the bearings replaced, only to find EVERYTHING was bad: bearings, axles, gears ect. I told him it had just over 300K miles and he said it sure looks like it, we called a junkyard that had an '85 Fifth Avenue 7 1/4 they no longer had it, but they were able to locate another '85 Fifth Ave 7 1/4 and have it shipped to their shop (they have a small repair shop also) so yesterday we drove there, amazingly that badly worn differential made the 40 plus mile trip there. Anyways the Fifth Avenue one works great, I do plan to find an 8 1/4 at some point, but I currently have MANY other things to worry about right now...thanks everyone for the replys
 

MoparDan

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The day before yesterday went to have the bearings replaced, only to find EVERYTHING was bad: bearings, axles, gears ect. I told him it had just over 300K miles and he said it sure looks like it, we called a junkyard that had an '85 Fifth Avenue 7 1/4 they no longer had it, but they were able to locate another '85 Fifth Ave 7 1/4 and have it shipped to their shop (they have a small repair shop also) so yesterday we drove there, amazingly that badly worn differential made the 40 plus mile trip there. Anyways the Fifth Avenue one works great, I do plan to find an 8 1/4 at some point, but I currently have MANY other things to worry about right now...thanks everyone for the replys
 
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