Need help with R&P (1 Viewer)

15 June, 2006 - Issue resolved (I think): Sorry to dredge this up again, but I finally have a cruiser that runs and a rear diff that seems normal. I origianlly used a cheap in-lb torque wrench to set pre-load. I recently tore the diff back down; pinion preload was way too tight. I was starting to see excessive wear in the inner pinion bearing race. So I believe the howling was the pinion bearings complaining. I set the pinion and carrier pre-loads to what felt good, reassembled it, and have put maybe a hundred miles on it. No strange noises that I can tell.

"what felt good" - somewhere between TDT (too damn tight) and LAATDH (loose as a two dollar hooker)

Thanks again for the help (last year). I'm driving my FJ again. Feels pretty damn good.
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I installed a rebuild kit in my rear diff and now have severe shudder and clunk problems. ('76 FJ40 stock gears). It begins howling as soon as I take off and gets louder with speed. I couldn't get over about 20 mph for fear. Also, at low speed (<10 mph) on deceleration with the clutch disengaged it clunked a couple of times.

Here's a brief history. I had a loose pinion bearing. The stake nut was tight but I could wiggle the pinion an 1/8". I also had moderate vibration and howl at speeds over ~35 mph. So I decided to rebuild the rear diff. (The driveshaft tubes are new, the u-joints don't have any play in them and are aligned correctly, pinion angle is fine, no play in transfer output, yoke isn't new but isn't worn out either, etc.)

I used several good references, including Charlie Glabe's writeup and tech notes from Randy's and a couple other troubleshooting/rebuild links on the net.

I shimmed the pinion bearings to ~16 in-lb preload, I added preload to the carrier until I had about 30 in-lb total, I measured backlash in 5 places - it varied from .007" to .009". The contact pattern is good in my estimation. I cleaned everything in Stoddard's. I was careful, I thought.

I didn't measure backlash or record the contact pattern before I took it apart. I will do some more troubleshooting wih your advice. And I'll remeasure backlash and record the contact pattern again. Should get to that tonight or tomorrow.

I'm leaning towards replacing the gears, but I'd be happier to know I did a sloppy setup and you can put me back on track. What do you think?

TIA,
theo

The shudder and clunk noise may be separate problems from the howling. Shudder is more likely a clutch issue. Did it do this before the diff rebuild? Clunk is usually too much accumulated rotational slop in the driveline.

Howling is typically due to bad tooth contact. If you drove around with bad bearings for a long time, the gears might have worn in a bad contact pattern that isn't going to be corrected by replacing the bearings. This should show up in the contact pattern.

Thanks, Pin. I was a little careless in my description. The only symptom I had before the rebuild was mild vibration at higher speeds, say 45 and up. No clutch issues that I'm aware of.

I think shudder is the wrong word. The shudder is actually howling (someone could have a field day with me right now.) It is audible and comes with major vibration that gets louder and faster with increasing speed.

The clunk is actually the sound I think a broken tooth would make, not the accumulated drivetrain slop that you mention and that I'm familiar with.

Tomorrow I'll take it out and count the tire rotations between clunks, maybe narrow it down to the ring (more rotations) or the pinion (fewer).

I've been driving it with a loose pinion bearing for some time - couple thousand miles I guess. The carrier bearings "looked" good, but so does a two dollar hooker at certain times.

I'll recheck the contact pattern and look for damaged gears and get back to all.

Update - still need help:

Took another short drive today. The clunk occurs while coasting in neutral from 30 mph or so down to 5 mph or so. It is more frequent than I thought - regular and rapid, several times per tire revolution. (It is probably there at higher speeds but I didn't test it.) The vibration is the way I described.

So I pulled the rear driveshaft and drove it in front wheel drive. The noises disappeared. I have other noises, but the clunk and vibration/howl are gone.

Pulled the diff cover and checked the contact pattern (excellent, centered in both directions) and backlash (unchanged). No broken or chipped teeth that I can see.

The rear slip yoke splines have some rotational play in them. I can't feel any play in the u-joints.

It seems to me that worn, howling, vibrating diff gears would still complain after removing the drive shaft. Not sure, though.

Any suggestions?

Try a new drive shaft. That could explain the clunk and vibration. Howling is usually a gear thing and it will change depending on whether it is on the drive or coast side of the tooth contact and it varies with load / no load. Hard to imagine you did anything wrong as long as the contact pattern, preload and backlash are correct.

How about the size of the contact pattern? If they were worn funny maybe the tooth contact area would be less.

Pin_Head said:

Try a new drive shaft . . . How about the size of the contact pattern?

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10-4 on the drive shaft and u-joints.

I thought the contact pattern took up every bit as much as the one Charlie Glabe put in his writeup. Only eyeballed it, though. I could take a digital pic and post it.

Maybe let's renew the shaft and u-joints first and go from there. Thanks, Professor. I'll be back

If it is good enough for Charlie, it is good enough for me.

Pin_Head said:

If it is good enough for Charlie, it is good enough for me.

Click to expand...

It's odd that you never see these two guys together. Hmmm.

Any update Theo?

I have a question for you Charlie. Do you see any problem with replacing just the pinion bearings, and reassembling with the shims and all just like they were?

Thanks.

If the pinion bearings need to be replaced because they have wore out, that metal has run through the carrier bearings too.


Yes, you could change just the pinion bearings, but if they are junk, I would change out everything.


Would be a waste of time and money to try and save some now, only to have it make noise later...



Good luck!


-Steve

spotcruiser said:

Any update Theo?

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I have to wait now until I get my tranny upgrade installed since the driveshaft lengths may change (sm465 out, nv4500 in).

Could be ages before I really know how I did on the diff rebuild - got a few honeydos to mix in too.

Bearings are machined to pretty close tolerances, so reusing the original shims with the same R&P should be real close as long as the shims are fine. You still need to check though.

you didn't by chance have the driveshaft seperate on you? you might check to see if your driveshaft is aligned properly.

Any updates on this?

PabloCruise said:

Any updates on this?

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Getting closer, but not there yet. I have the TBI rebuilt and the nv4500 bolted up. Shoud have the drive train in place today. Have simplified the harness, got the pinouts, need to make the connections. Still have to run fuel lines.

I MIGHT have it running under it's own power in a week or two. Can't get back to the diff problem until then.

ps - Ige, I had the driveshaft out, but I've been aware of phasing for awhile. Pretty sure I had it right. Will make double sure when I test again.

Still have to rebuild the front axle and install the ARB. Might not get that far before I have to be in the Cascades to represent LCs in a "Jeep Jamboree" next month!

Seriously confused - solved!

Howdy!

I apologize if this is covered elsewhere. The search fcn got me to this post and I started in...

I read through Charlie Glabe's article, and then dug into the Toyota Chassis and Body manual to read up on the rear diff.

There is where I got pretty darn confused! The FSM has you set up the drive pinion and measure pinion preload. I believe at this point the ring gear and carrier are not present in the third member.

The FSM states:
Specified Preload (starting)
New Bearing 16.5-22.6 in-lb
Reused Bearing 7.8-11.3 in-lb

Then you keep going, put the ring gear on the carrier and install that. Then set your side bearing preload. Then you measure the overall preload.

I just got the issue that was hanging me up...

The FSM states:
Specified Preload (starting)
(For both new and reused bearing) 3.5-5.2 in-lb + DRIVE PINION PRELOAD.

I kept missing the + DRIVE PINION PRELOAD part and wondering how the hell the overall preload part could be less than the drive pinion preload.

So, it sounds like you can evaluate a third member with ring gear carrier installed by giving the pinion a spin and the acceptable range of starting preload could be as low as 11.3 in-lbs OR as high as 27.8 in-lbs?

Man, setting up diffs is a little trickier than I thought!

it's a lot of back and forth if you don't have the right tools and want it right.

PabloCruise said:

So, it sounds like you can evaluate a third member with ring gear carrier installed by giving the pinion a spin and the acceptable range of starting preload could be as low as 11.3 in-lbs OR as high as 27.8 in-lbs?

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Is this correct? Just seems like a wide range!

Almost right.
If you reuse your pinion bearings then the range is 11.3-16.5.
If you replace the pinion bearings the range is 19-27.8.

Also, one of the writeups I found was by a mechanic who regularly put several times the recommended preload on the carrier bearings and claimed to never have a problem. FWIW.

bump (see edited 1st post)

PabloCruise said:

There is where I got pretty darn confused! The FSM has you set up the drive pinion and measure pinion preload. I believe at this point the ring gear and carrier are not present in the third member.

Click to expand...

Personally, I think that it is easier to set the pinion depth first, especially if you are changing R&P where you need to set the depth. The reason is that if you change the pinion thepth, then you have to reset the pinion preload. Resetting the preload isn't a huge job if you have the complete set of preload washers because you can calculate the size of the washer from the change in pinion depth. It is a PITA resetting it if you are sanding down the washer to get it right.

You don't need to have the preload set to check the pinion depth and contact pattern; you just need to have it tight. Once you are done getting the depth right, then you only have to set the preload once. I wrote it up the way it says in the FSM, but I think it is less work to set the pinion depth first, unless you get lucky and get right on the first try.