How much diff spider gear wear is acceptable?

[SOHCman]

Just changer the gear oil in my sterling 10.25 12 bolt. While had the cover off I was looking around in there and noticed some decent wear on the spider gears (open diff). I could rotate the pinion left and right maybe 1/8 to 1/4 inch and visibly observe the spider gears move as the slack was taken up engaging the shaft gears.

This unit is supposedly a reliable diff, but with 174k on it and unknown previous maintenance on it I am wondering how long I have on it before a rebuild or maybe a upgrade to a locker or something is necessary? Ring gear still has a centered wear pattern but it does reach most of the surface toward the toe and heel. Maybe 1/2 inch left on each end.

I have just moved to syn 75w-140 from syn 75w90 thinking this could cushion the spiders enough to prolong it's life. Good idea? Thanks.

 

[bmwtechguy]

My first question would be, was it quiet with the 75W90 and is noticebly more quiet with the heavier lube in it? Also if there is noise, is it more while you are turning and the spider gears are working? The only problem I see with some wear in the spiders is more drivetrain lash when going on and off the throttle or going into reverse. That is, if the diff is currently quiet. It should still give you long service. Are you towing with it? Open diffs just have so much less debris floating around, even if minimally serviced. This alone gives them a fighting chance at a long life. Curious here...what lube did you use? What lube was in there? So many questions....sorry

 

[SOHCman]

Thanks for the reply,

My truck has a rumbly exhaust, so any gear noise from the diff is hard for me to hear. There is however an audible clunk when I change from decelerating to accelerating, and it's a manual trans. Honestly I thought the noise was coming from the trans gears being loose, it "sounds" like it's coming from right below the cab. Perhaps it is the diff?

I don't currently tow with it but the original owner supposedly towed a race car around to tracks with it. The original lube I dropped out was filthy and full of black sludge (iron) like you would expect from a diff, and there were bubbles where the gear oil was clinging to the gears. I assume this meant the anti foam additives had worn out, and likely the oil had been used too long.

I put in valvoline 75w-90 full syn about 7 months/10k miles ago and when I dropped it the other day it was dirty brown and there was a good amount of sludge again. This was a "flush" so to speak. I'm sure the axle tubes were full of wear particles. I noticed there were no bubbles this time.

I may mount a recorder or a gopro next to the diff and the trans and see if I can tell what noises are coming from where. I would like to keep the truck for a long time.

 

[bmwtechguy]

A clunk like that could be from a couple different things, really. Driveshaft u-joints, rear diff gear lash, etc. Hopefully it is NOT from your manual gearbox, or it will need attention sooner than later. Driveline clunking noises can be hard to pinpoint from just driving as the noise can sound like it is coming from more than one area, depending where you are sitting in the vehicle.

 

[mattd]

check the yoke on the output shaft of the transmission, as well as the slip yoke (if applicable).

 

[SOHCman]

Originally Posted By: mattd
check the yoke on the output shaft of the transmission, as well as the slip yoke (if applicable).


What would I check on the output yoke from the transfer case? Rotation? In neutral, the yoke will rotate back and forth perhaps a quarter of an inch until slack is taken up. Same with the diff, it all rotates a bit by twisting the shaft with my hand. The slip-yoke has a small amount of wiggle also if I twist on both sides if it.

I am going to disconnect the driveshaft and slide the slip yoke apart to clean and grease it with synpower moly grease. It always baffles me how driveshafts can not have zerks installed.

I have gone to heavier lubes in the diff and trans, but the rotation is still there. This seems to have lessened the issue, but it could be placebo. Going to go heavier in the transfer case and see what happens.

 

[SOHCman]

Originally Posted By: bmwtechguy
A clunk like that could be from a couple different things, really. Driveshaft u-joints, rear diff gear lash, etc. Hopefully it is NOT from your manual gearbox, or it will need attention sooner than later. Driveline clunking noises can be hard to pinpoint from just driving as the noise can sound like it is coming from more than one area, depending where you are sitting in the vehicle.


Yes, hopefully it's not the trans but I may pick up a spare if the opportunity arises just in case. There was loud gear whine with ATF like it calla for, less with synchromesh, and now much less with RL MT90.

 

[SZR48207]

I'll be interested to see what is posted. I have the IDENTICAL concern with the Ford 8.8" on my F150.

I think my backlash is maybe up to an inch excessive, though.

I wouldn't mind putting in an LSD or auto locker, but I just need to know how much time I have left on the open diff.

 

[SOHCman]

Originally Posted By: Reddy45
I'll be interested to see what is posted. I have the IDENTICAL concern with the Ford 8.8" on my F150.

I think my backlash is maybe up to an inch excessive, though.

I wouldn't mind putting in an LSD or auto locker, but I just need to know how much time I have left on the open diff.


I would suggest trying a 75w-140 syn like valvoline synpower, can't beat the price. After switching to it myself I have noticed less of a clunk between accelerate/decelerate and I just towed a big wind sail of a trailer without any drama, so I think this might be the path for the rest of it's life until I decide to get a locker of some sort.

 

[SOHCman]

Originally Posted By: Reddy45
I'll be interested to see what is posted. I have the IDENTICAL concern with the Ford 8.8" on my F150.

I think my backlash is maybe up to an inch excessive, though.

I wouldn't mind putting in an LSD or auto locker, but I just need to know how much time I have left on the open diff.


One war to make sure it's not play in the trans, block the wheels and put it into gear then try to ratate the drive shaft. Mine locks up solid in gear, so all my play resides in the diff apparently.

Perhaps someone else in here is an expert on diff life, but I would wager that once it starts howling/ whining it's time for a rebuild. Not positive play us as much an indicator as an an annoyance.

 

[KenO]

Unless they look like this, make crazy noises, or something else equally worrisome - then don't worry about it. it's an open diff.

 

[andyd]

Maybe apples and oranges, but between the end play in the crankshaft and the spider gears in a Grand Wagoneer. They would roll a foot when left in park. And Take off with a clunk as the various lashes took up under load. Just keep the diff full and dont do anything silly.

 

[MolaKule]

The differential or spider gears ride on the crosspin or stud and it will wear making a noise.

Try a higher viscosity synthetic and see if that prolongs the life.

If the diffy fluid has not been changed, then you might have a lot of wear on the components.

 

[SOHCman]

Originally Posted By: MolaKule
The differential or spider gears ride on the crosspin or stud and it will wear making a noise.

Try a higher viscosity synthetic and see if that prolongs the life.

If the diffy fluid has not been changed, then you might have a lot of wear on the components.


Thanks for the suggestions,

I am currently using A thicker oil, valvoline synpower 75w-140, on my last change aprox 8-9 months ago at 164k~ miles there was a fair amount if wear. Black sludge like you find in an auto trans pan. I doubt it was the original oil though.