Diff rebuild by "pro" not going well

Piratetip

Far From Maddening Crowds
Staff member
Super Moderator
Dec 30, 2005
1,123
32
48
37
MKE, WI
Richmond might be ok.
But I agree with Andrew, stay away from SVL / Dana gearsets.

They key is getting another with 27 spline pinion.
Otherwise go with a new Nitro gearset, you will have to convert the seal/flange/nut to the larger 29 spline.

Otherwise find another good used OEM gearset
 
  • Like
Reactions: alcyon

Dave 1jz

New Member
Feb 16, 2010
9
2
3
rotterdam
Very nice informative topic. I also rebuild my own diffs. Piratip already gave much useful information. My experience with solid spacer is not great. A crush sleeve works very accurate and worry free. For setting pinion depth i honed out a old top bearing, so i can remove the shaft easily.

Wonder at what situation one would need a solid spacer, 500+ whp? or 600+Nm of engine torque?
 
  • Like
Reactions: alcyon

alcyon

Member
Jun 15, 2017
61
12
8
Kuala Lumpur
I did some investigation today. I know for sure that the noise is happening when the rear wheels are on the ground and moving forward, even though the speed is very low (15 to 10kmh) and transmission is D (engine braking) as well as N (no engine braking) . So naturally I suspect the ring and pinion. But from a few process of elimination I am not sure now.
I jacked up the rear and placed on jackstands. Put Trans in N and parking brake off.

1. I placed some wooden blocks under left wheel. Turn right wheel with my hand as fast as I could, the grinding/rattling noise not present.
Moved the wooden blocks to right wheel, turned left wheel as fast as I could, also no such grinding rattling noise. This is basically forcing the ring gear to turn pinion gear, simulating a coast condition.
2. Removed all wood blocks, went underneath, used both hands to move both wheels forward, forcing ring gear to turn pinion gear and prop shaft. Couldnt move wheels as fast as before but also no grinding rattling noise, and my head was right under the diff so i can hear very closely.
3. Removed prop shaft from diff and tried to rotate companion flange with one hand, it was tight and initially difficult to break loose , once break loose, rotates smoothly all around in both directions.

Conclusion, pinion preload is intact. Ring and pinion also should be ok.

4. Started up car suspended, put in D, rear wheels moving at 20kmh, put in N, still smooth until wheels stop. Put in D accelerate to 50kmh, move gear to N, coasts smooth all way until wheels stop.

5. While trying to break the propshaft loose from diff in step 3, I pulled handbrake and put in D(4 prop shaft bolts removed of course), but noticed the left rear wheel wasn't moving, right rear wheel moving, looks like handbrake adjustment uneven, then checked both rear wheels at 12 to 6 position and give it a shake, left rear wheel has small amount of shake. Proceed to torque down left rear wheel cv axle nut, no more shake. Considering the supra uses a one piece bearing, I would think tightening the CV axle nut shouldnt affect the shimmy of the wheel hub.
6. Seeing that left rear parking brake force is greater than right rear, I remove left rotor and inspected the parking brake mechanism against TSRM, see nothing wrong, so proceed to contract the parking brake shoes to weaken the brake force.

Now I am beginning to suspect either left rear wheel bearing, or cv axles. It could be I didn't assemble back the tripod joint to the exact chamber (3 possible combinations) of the inner joint, causing a rubbing noise on decel. Or left rear wheel bearing. Now why do I suspect this bearing? Months ago while the skyline dude was rebuilding the diff, I tried removing the CV axle to rebuild, but it was stuck. So I removed the whole rear knuckle and asked him to press out the cv axle from the hub. Since he used a hydraulic press to force it out, he could have damaged the bearing internally, by just a little.
The 3rd cause could be the uneven parking brake adjustment , of which I just corrected.

All that''s left now is to test drive the car, hopefully the sound is gone. I will know in a few hours.
 
Last edited:

Dave 1jz

New Member
Feb 16, 2010
9
2
3
rotterdam
Not saying my situation is similar to your problem, but recently i replaced the pinion bearings (with crush sleeve) due to a slightly too high preload on the solid spacer and perhaps vibrations of the propeller shaft. During installation of the rebuild diff i found that the propeller shaft universal joint at the diff flange had a slight radial movement. I had a (professional) rebuild and balanced aluminum one-piece shaft already laying around and fitted this one instead of the old two piece. This made a world of difference in both total drive train backlash/slack and vibrations. And i only had like 0.4mm radial play by hand. Makes me wonder how all three universal joints were faring under load. So the two-piece is definitively due for a rebuild after 30 years of service. Something to consider.

Also regarding setting the pinion bearing preload, there was something about constant turning and break away. I fully agree the measurement should be at constant turning. However, the break away torque should not be much higher than constant turning. Using a crush sleeve helped me greatly to slowly tighten the the nut to initially remove the clearance (already at 300+Nm) and build up the 'constant turning' torque without a significant increase of breakaway torque. If you experience a relatively high step between breakaway and constant torque, chances are you overshot the target value.
 
  • Like
Reactions: alcyon

alcyon

Member
Jun 15, 2017
61
12
8
Kuala Lumpur
Not saying my situation is similar to your problem, but recently i replaced So the two-piece is definitively due for a rebuild after 30 years of service. Something to consider.

Also regarding setting the pinion bearing preload, there was something about constant turning and break away. I fully agree the measurement should be at constant turning. However, the break away torque should not be much higher than constant turning. Using a crush sleeve helped me greatly to slowly tighten the the nut to initially remove the clearance (already at 300+Nm) and build up the 'constant turning' torque without a significant increase of breakaway torque. If you experience a relatively high step between breakaway and constant torque, chances are you overshot the target value.
My prop shaft was rebuilt and rebalanced. It seems smooth at the joints and no vibrations felt under me.
As for the pinion preload, i was getting about 8 in lb constant turning. The breakaway was over the scale of the wrench, but then again the upper limit of that wrench is about 25 in lb only. Through my hand the breakaway torque doesnt feel that high, as I am no gorilla, only 5ft 10" and 165lbs, so I guess its ok.

Edit Saturday the 24th Sept 2022. a thought just occurred . Have not tested tested the car, but I have a baaad feeling the noise will still be there. You see, with all tests done yesterday, its with the oil cold. Plus with the rear jacked up, all the cold thick oil is submerging the whole pinion, giving extra cushion between the gear tooth.
I actually need to do the hand rotate test with oil drained from diff. If the ring and pinion is good, forcing the ring to turn the pinion at hand speeds should not cause a noise. If it does, its a sure sign the coast side of the pinion is bad. Besides, there will still be residual oil over the gear tooth.
It could have happened when the skyline dude rebuilt the diff with too much backlash, not enough carrier preload, and no pinion preload, causing the pinion to wobble around on coast and damaging the coast side.
It is important to be able to replicate the conditions on coast on the diff before putting the diff back on the car to save a huge amount of work .
I am also prepping the tiny video cam to go over the rear subframe body mount.
If with these conditions I can replicate the sound then for sure its the ring and pinion. I might go with this local brand . They claim their gears are easy to setup up and have pinion depth inscribed. Its also 1/3 the price of OEM gears. Also i need to wait a 5 weeks for OEM gears.
1663991542600.png
 
Last edited:

alcyon

Member
Jun 15, 2017
61
12
8
Kuala Lumpur
@Piratetip here is a video.

from the website onallcylinders , this is what I would describe as the closest symptom

1664029983960.png
I dont know why but the camera could not capture the sound properly. I was only able to spot the sound right after 13:10 and 13:45 mark, pay attention when I decelerate. sounds like a cyclical knock. The funny thing is i heard the sound in the car all the time i decelerate, and its certainly coming from behind.
Maybe i should record from inside the car near the transmission tunnel.
 
Last edited:

Piratetip

Far From Maddening Crowds
Staff member
Super Moderator
Dec 30, 2005
1,123
32
48
37
MKE, WI
I can kind of hear the noise.
What speed were you going?

Next step would be seeing if it's tied to wheel rotations.

Can't tell much from my end but the knocking sounds too slow to be tied with wheel rotations. (Hitting the same spot again and again on the ring gear)

I have some annoying poly suspension bushings that knock / pop / creak randomly.
Drives me crazy sometimes.
Someone else may interpret the noise as the car falling apart.

Sometimes quite difficult to pinpoint noise and it's cause