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Excess Rear End Backlash

Discussion in 'Differential & Driveline' started by 79dentside, May 19, 2020.

  1. 79dentside

    79dentside Full Access Member

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    Hi all, I may have 2 situations, not sure yet. Basically I was doing u-joints and decided to service the rear end. I noticed that there is a newer ring and pinion (4.10 gears) and new fluid.... but there is some slop in the spider gears. This results in a clunk when going into reverse which am not too worried about really, but I do notice a very faint howl around 40 mph; load has no effect. It resonates when in the gas or coasting but we are talking a very quiet howl. It starts at 40 mph, then disappears. I am wondering this is likely related and if I can fix both issues at the same time? Or is this another bearing noise? It almost seems to be rear right, but noises are strange and resonate. No other issues or noises. Or should I even address it? It’s a peg leg rear end in a 12 bolt housing. Thanks.
     
    Last edited: May 20, 2020
  2. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    If you could, do a rough check of the pinion slop up-down/side-side (rotational play irrelevant to this test) on the driveshaft side of the pumpkin. My guess is you might find it to be sloppy. It sounds like you may still have the cover off so if you can, take some good pics of the ring and pinion gears and post so we can see the wear pattern. You may have already done this and there may not be visible wear if they’re relatively new. If someone replaced the ring and pinion without doing a master rebuild on a well-used unit, especially with a shot pinion bearing and who knows what else, that would qualify in my book as a half-assed job. Not your fault, of course.
     
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  3. eskimomann209

    eskimomann209 Supporting Member Supporting Member

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    4.10 gears depending on the axle and previous gears, there’s a carrier break that the PO might have ignored. It’s possible to get it close but it’ll never be right. Pics would be nice if the carrier and some measurements.
    I hate when someone else swaps new shit then sells. Makes me feel like they were dodging something or hiding another.
     
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  4. 79dentside

    79dentside Full Access Member

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    Full disclosure, I did not count the teeth, but when I looked up the number, it came up with 4.10. I should have confirmed. It turns about 3,500 rpm at 60 ish mph.

    I have it buttoned up and new lube in it. So I believe the gear set was done in 2007 along with the GM engine. “A” previous owner painted everything that they removed ORANGE... motor mount bolts... cab bolts... pinion... anyways, the engine is dated 2007 behind the flywheel when I had it out and I know the truck was parked for years after that. I estimate about 23,000 miles on the rear gears if it was done when the engine was... again, both have orange markings so I wonder if it was done at the same time and then parked.

    There were no chips/broken teeth/gouges in the teeth. The spider gears look older than the ring and pinion just due to coloration. Might be hard to tell in the picture.

    This is the only picture that I got.
    [​IMG]
     
    Last edited: May 20, 2020
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  5. Turbo4whl

    Turbo4whl Full Access Member

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    If you think the spider gears are too loose, they may have been assembled without the shim bushing(s) on the back side of the gears. One each on both the side gears and spider the gears.
     
  6. 79dentside

    79dentside Full Access Member

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    Oh wonderful haha... yeah, unfortunately they are on the loose side. I even considered welding them up and making a locker because I couldn’t figure out the slop while it was open. I talked myself out of it based on other wear that it would cause by locking the axles.
     
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  7. 79dentside

    79dentside Full Access Member

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    Relative to the howl that comes with speed (not at all dependent upon in throttle or decel)... Might I add that originally I did the differential service because the pinion seal was leaking and the pan gasket was seeping and I wanted to address both. The pinion nut was siezed and could not get it off to replace the seal, so I put new fluid in and it no longer leaks. Not sure if that throws anything helpful into the mix, but the pinion seal was leaking a fair bit and running down the pumpkin.
     
  8. Joshua Keith

    Joshua Keith Full Access Member

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    I had the same issue. Ton of slop in the driveline. Do you have play in your driveshaft? Try grabbing the drive shaft near the pinion and wiggle it. My spider gears were a little worn, but my main issue was the pinion nut came loose and was backing off. Replaced the spider gears (50$), checked backlash .06-.10 mm, installed new crush sleeve and torqued it down until I hit 10 inch lbs of bearing preload. 10 inch lbs for worn bearings. Huge difference in gear engagement.
     
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  9. Joshua Keith

    Joshua Keith Full Access Member

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    Try replacing those spider gears. Don’t have to take the pinion out for that. Maybe you can save the gear oil you just put in.

    CBE727AC-87A8-47B4-B04F-4268A68E508D.jpeg
     
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  10. 79dentside

    79dentside Full Access Member

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    I’m not too worried about needing new gear fluid haha. Yeah the spiders have slack. When I had the driveshaft out, the pinion spun very smooth by hand, it didn’t hang up or grind. I would assume a person put pinion bearings in when they put the new gear set in... can’t imagine that they wouldn’t. Maybe I have a bad wheel bearing causing the howl?

    Where would you all suggest getting spiders from? It’s an open diff which really sucks. Maybe it’s time for an upgrade if there is an economical option? It’s got a crate GM 350 that spins the tires way too easy. I bought this to be a winter beater and it gets stuck too easily, that’s why I considered killing 2 birds with one stone by welding the diff... get rid of my slip and fix my traction issue, but I feel that it will cause a lot of problems down the road.
     
    Last edited: May 20, 2020
  11. Poppy 87

    Poppy 87 Supporting Member Supporting Member

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    Brandon, the symptom you describe sounds more like a pinion bearing than spider gears. The gears in your picture look pretty good to me. Spider gears usually don't have intermittent noise.
     
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  12. 79dentside

    79dentside Full Access Member

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    Wonderful haha.. the gear do have slop. I rocked one of the wheels back and fourth and could see the slop and hear the slop when I had the cover off. I can confirm, there is spider gear slop.

    As for the pinion bearing... I watched videos on that this morning as I wondered that myself. This rear ring/pinion (and I hope bearings....) doesn’t have a whole lot of miles on it, like I said everything that the PO touched, they painted orange (including engine bolts and that was done in 2007) and then parked it for years, then was used as a farm truck. All the tires are 15 years old with some around 70-80% tread, I don’t believe they had a lot of miles on the pinion/ring. As for the rest of it, the truck supposedly has 113,000 miles.
     
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  13. 79dentside

    79dentside Full Access Member

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    I needed to grab gas in the truck today so I did a little testing. Looks like the noise is only from 40-50 ish mph and it’s a light howl that disappears. Got home from getting gas and I jacked the back end up and had someone get in the truck to man the controls while I went around with a stethoscope, but it was quiet when performing the speed test with it lifted... then I realize only the drivers wheel is spinning.... I am wondering if it’s not a wheel bearing on that passenger side like I wondered. I honed in to that pinion bearing and it is as quiet as can be from what I was seeing. Nothing was making noise at 40, 50, 60 ... mph with it hoisted off the ground, but that back right wheel was not really spinning.
    [​IMG]

    As for the spider gears... this open diff (or so I think???) is really ticking me off. I think this is an open, but my last open diff would spin the wheels in opposite directions. This one will spin both OR 1.... it’s all over the spectrum really.

    Can someone explain what I got going on here? It starts with 2 rolling forward, then 1 wheel just stops and it begins to open diff.



    Thanks
     
    Last edited: May 21, 2020
  14. TPISly-C10

    TPISly-C10 Full Access Member

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    mine was bad too ..change unit for posi at the same time :)

    _DSC3572.jpg

    _DSC3578.jpg
     
  15. WFO

    WFO Full Access Member

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