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Knocking noise front differential

Tiny
WALKINGTOOLBOX
  • MEMBER
  • 1992 CHEVROLET 1500
  • 4.3L
  • V6
  • 4WD
  • MANUAL
  • 236,000 MILES
When in neutral there is a knocking noise that gets louder with speed. The noise persists with 4wd drive line out, the sound is coming from the front differential I believe. The CV axles are in great shape, front end is solid. So I do not believe it is the problem. Was thinking maybe the pinion yoke area but I am not entirely sure. Thoughts and experiences with this all would help thanks.
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Sunday, October 21st, 2018 AT 3:40 PM

10 Replies

Tiny
ASEMASTER6371
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Good evening.

It sounds like you may have chipped a tooth off of the ring or pinion gear. I would remove the front cover and inspect the gears for any damage. I bet you need a ring and pinion.

Roy
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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Alright, I will have to do that. Question, how do I figure out my ratio for my front differential?
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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I climbed all over the thing and could not find a tag or stamp of it, am I just missing it or is it just in a spot I missed or can I find it another way?
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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Okay, count the number of teeth on the pinion gear and then count the teeth on the ring gear. Then divide the two together. That will give you the ratio.

It will be like 3.08 or 3.43 or 3.73 or 4.11.

Roy
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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Does the front ratio match the rear? If so mines a 3.73.
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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It has to match or the four wheel will not work.

Roy
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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3.73 it is then. Now I have not gotten into a front differential before, this one here does not seem to have a cover, so I would have to drop it then split apart. Other then the straight forward of removing this and that to get it out is there anything special I need to do or take note of when taking it out and apart or is it all straight forward? Does it take a gaskets for the center split area or is that just Permatex? If so what variant of Permatex should I use? Thanks for all your help.
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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Procedure for removal:

1. Remove differential side bearings using a suitable puller or press.
2. Remove ring gear attaching bolts and the ring gear.
3. Scribe an alignment mark on both case halves, then remove bolts holding case halves together.
4. Tap top half of case loose from bottom, then remove top half and all internal components.
5. Position new washers on side gears, using a small amount of lubricant on side gear hubs.
6. Install pinion gears and new washers onto cross shaft.
7. Assemble top half of case to bottom half, using alignment marks made during disassembly. Tighten bolts alternately and evenly.
8. Install ring gear and torque bolts alternately in stages to 110 ft. Lbs on 10-1/2 inch axles, 220 ft. Lbs. On 11 inch.
9. Position side bearings onto case and seat bearings using a suitable driver. When installing second bearing, support case with suitable pilot to prevent damaging case of opposite bearing.
10. Determine side bearing shim requirements as follows:
a. Place bearing cups over side bearings and install differential case into carrier, with pinion removed from carrier.
B. Position original shim in ring gear side, then install bearing caps and tighten just enough to retain in place.
C. Install a dial indicator on carrier with indicator button contacting back surface of ring gear.
D. Position two screwdrivers between bearing shim and carrier on ring gear side of case. Apply force to screwdrivers to move differential case as far as possible away from dial indicator. With force still applied, set dial indicator to 0.
E. Reposition screwdrivers on opposite side of differential case and force differential case back toward dial indicator. Repeat sequence several times until same reading is obtained.
F. Add thickness of shim to dial indicator reading and record the result.
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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Sorry this took so long to get back to you, but turned out to be a shot pinion bearing. Which explains the more then normal vibration in 4wd, teeth weren't broke but chewed really bad and flattened. Its rod that engaged it all was also bent almost half over. Not sure how it even went into 4wd. Just gonna buy a used one cant afford a full rebuild. Thanks for help.
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Friday, May 14th, 2021 AT 11:33 AM
Tiny
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You are welcome.

Always glad to help.

Roy
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Friday, May 14th, 2021 AT 11:33 AM

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