differerntial diagnosis

everything but the drivetrain

Moderators: Greenleaf, BC847, Richie O

differerntial diagnosis

Postby jethro » Fri Sep 25, 2015 10:06 pm

Finally got round to taking the cover off the rear diff. (ford 10.5 inch)
Could see there was a LOT of slop in the pinion- in and out and laterally.... lots.
Got the front seal off and pulled the front pinion bearing out and off the shaft with a pick. (not good..)
Then popped the cover off the back. Oil running out looked like vegetable soup color- obviously had water in it.
Washed some of the gook off the carrier and ring gear. can see some fine rust pitting on the face of the teeth
on the ring.
Also I see some helical scars on the body of the carrier where it appears that the end of the pinion has been digging
in from having a LOT of end play.

I was going to replace the axle bearing and seals anyway while I was in there..........

Havnt gotten anything out yet- but The inside of the carrier might not be pitted like the ring - will see when I can
get it apart.

Is there ANY tolerance for pitting on the tooth faces of the ring ????? just need to figure out if the ring/pinion are
salvageable- and the same with the carrier assy. The truck had 180k miles on it.

On another observation- whoever had previously done the suspension lift- looks like they rolled the axle backwards a little
to get the front of the rear diff pointing a little upward towards the back of the transmission. That angle sort of makes the
front pinion bearing like a "high point" to some degree as far as the internal oil level. I am wondering that if the oil level
got a little low the front pinion bearing could be starved for oil first- then it would go to crap and then open up to let
the pinion get end play and then the pinion gear could touch the carrier.
Do I want to rotate the diff back to horizontal (or closer to horizontal) and remove a couple of the jack-up blocks-
Was going to lower some anyway later- I don't want to loose a bearing because of that lift foolishness-----

havnt done a diff overhaul before so I have to self educate as I go ! ( have worked as a machinist and aircraft mechanic-
so I hope I can slowly figure it out )

I wont be pulling or hauling heavy loads - but I DO want a trouble free diff.
(going to drain the tranny and the front diff just in case the previous owner went through a stream and it turned out to be
a river- knew somebody that did that with a 4x4 van- 5 feet deep- looked like a puddle of dirty water. Sucked water into
the heads and blew them off the block. I expect that was expensive.

Tim

PS. - found this video- looks pretty educational on doing preloads and backlash-
https://www.youtube.com/watch?v=dAqAqODmcj4
Seems like a good teacher !

I will also have to find some on the limited slip parts too.
jethro
fuel screw!!!!
 
Posts: 432
Joined: Sat Mar 08, 2014 12:32 am

Re: differerntial diagnosis

Postby matthewh » Sat Sep 26, 2015 8:15 am

In terms of pitting on the ring gear, in a perfect world, you want zero pitting on the meshing faces of the gear. Every spot of rust that has eaten into the face is a wear point, and excessive wear will occur. As for rust elsewhere, as long as its not crazy, id run it. The gear face is the critical point for longevity.

For the pinion angle issue. To solve that, you'll have to reassemble everything and set the truck on the ground and measure the tcase output angle and the pinion angle. Due to the lift, they may have rolled the axle to achieve a proper driveshaft angle to keep vibration down. You want the tcase to be equal, or 1* higher than the pinion. The idea behind the 1* difference is when you accelerate, and "wrap" the axle, it makes up that 1* and the angles are now equal.
If the angles are off, you'll need to either cut and reweld the leaf perches, or buy shims that go between the springs and the perches to solve the angle issue
'93 W350 5spd Getrag, 4.10 gears, 83k miles and counting, Mods: LPPP AKA Ma Dually
'54 Dodge M37 6.2/700R4/205, 5.89 gears, WC rear axle
matthewh
14mm rotor
 
Posts: 633
Joined: Mon Feb 18, 2013 3:07 am
Location: Boyne City Michigan

Re: differerntial diagnosis

Postby jethro » Sat Sep 26, 2015 9:37 pm

A closer look in the daylight today- the ring gear has some fairly nasty looking patches of pitting on both faces.
I cant see relying on that thing for long term. I think it will have to be trashed !
I am making an attachment to mount on my engine dolly that I can lay the axle across so I can have the diff at a
reasonable level for precision work. Two uprights with semi-circle cups for the axle tubes and something to prevent rotation.

Its got quite a few jack-up blocks from the lift. Maybe they ground off the perches so it could rotate ? would the U-Bolts
squeeze alone prevent rotation ?

The back of the frame is so high I will have to figure out how to get my jack stands up that high ! (from axle to frame)

I probed into the little sump area at the bottom- there was a lot of sludge there- maybe a full shot glass full !
I will try to see if it sticks to a magnet.

when you say the 1 inch difference between the t-case and diff.- this is the REAR DIFF- the drive shaft is going into the
transmission output shaft. Are you saying that if I project a line out of the pinion shaft- that line should hit the transmission about 1 inch below the transmission output shaft ???????


Thanks for the reply !
Tim
jethro
fuel screw!!!!
 
Posts: 432
Joined: Sat Mar 08, 2014 12:32 am
Top

Re: differerntial diagnosis

Postby matthewh » Sat Sep 26, 2015 10:11 pm

1 degree difference is ideal.
Say you reinstall the axle and driveshaft, and you place a protractor on the top of the shaft at the tcase end, you'd get say 82*, or 82 degrees. (82 is an example number)
Place the protractor at the top of the driveshaft, axle end, and you should ideally see 82*, but 81 would be acceptable. Any more or less that that 82 and you'll have to shim your rear axle to get within specs
'93 W350 5spd Getrag, 4.10 gears, 83k miles and counting, Mods: LPPP AKA Ma Dually
'54 Dodge M37 6.2/700R4/205, 5.89 gears, WC rear axle
matthewh
14mm rotor
 
Posts: 633
Joined: Mon Feb 18, 2013 3:07 am
Location: Boyne City Michigan
Top

Re: differerntial diagnosis

Postby jethro » Sun Sep 27, 2015 9:05 pm

OK- Thanks-
Sounds like + or - about 1 degree.
When you mention shimming the rear axle- I would have to be doing something to "roll" the pumpkin forward or back-
My axle does not seem to have a welded-on triangular platform for the spring to sit on-
Just to look at it - it would appear that all it has is the U-Bolts.... (like where would a shim go? -) but I will know for sure in a day or two when it comes off.

The angle measurements sound like a good place to use one of those electronic digital level.

Thanks-
Tim
jethro
fuel screw!!!!
 
Posts: 432
Joined: Sat Mar 08, 2014 12:32 am
Top

Re: differerntial diagnosis

Postby matthewh » Sun Sep 27, 2015 9:38 pm

Preferably -1degree, but as close as you can.
To shim the rear axle, you would purchase degree shims close or at the difference in degrees, and they bolt to the bottom of the springs, between the springs and spring perch. Usually you have to remove the leaf spring center pin, and replace it with a longer one that locates and bolts the shim to the spring pack. Then you reassemble, and double check your measurement.
'93 W350 5spd Getrag, 4.10 gears, 83k miles and counting, Mods: LPPP AKA Ma Dually
'54 Dodge M37 6.2/700R4/205, 5.89 gears, WC rear axle
matthewh
14mm rotor
 
Posts: 633
Joined: Mon Feb 18, 2013 3:07 am
Location: Boyne City Michigan
Top

Re: differerntial diagnosis

Postby jethro » Wed Sep 30, 2015 9:23 pm

Thanks Mat-
I will try to find one of those "angle finder" devices. Maybe cheaper than an electronic level.

Tim
jethro
fuel screw!!!!
 
Posts: 432
Joined: Sat Mar 08, 2014 12:32 am
Top

Re: differerntial diagnosis

Postby matthewh » Thu Oct 01, 2015 12:09 am

Iirc there $20 at home depot or lowes. There handy for other things as well, plus its an easy excuse to buy another tool.
'93 W350 5spd Getrag, 4.10 gears, 83k miles and counting, Mods: LPPP AKA Ma Dually
'54 Dodge M37 6.2/700R4/205, 5.89 gears, WC rear axle
matthewh
14mm rotor
 
Posts: 633
Joined: Mon Feb 18, 2013 3:07 am
Location: Boyne City Michigan
Top


Return to Chassis

Who is online

Users browsing this forum: No registered users and 3 guests