Raspy Scratching Noise Periodically on Acceleration

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Isuzu Faster
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Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Sun Sep 08, 2019 8:00 pm

Hello folks,

I’ve noticed that from years back, there would be a faint “clang” from around where the transmission is upon accelerating in first gear from a complete stop. Never really was a problem.

Well lately, this faint clang has periodically changed to a “ka-pling!” followed by a consistent raspy scratching noise that increases with speed. It’ll accompany throughout all four forward gears until a couple intersections later, when it would be fine with no noise again whatsoever.

I’m guessing...maybe a u-joint going out? I don’t think it’s the transmission (fingers crossed...I’ve got the “stronger” ‘86 4-spd). Wanted to consult with you all before I pay to have this go up on a lift in the coming days. Many thanks in advance!
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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puttputtinpup
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Re: Raspy Scratching Noise Periodically on Acceleration

Postby puttputtinpup » Sun Sep 08, 2019 8:51 pm

Jack up one rear wheel w tranny in neutral. Chock the other tires. Rotate the one wheel which will turn the driveshaft. Listen for creaking sounds. Personally, my hunch is u-joints, but the popping-clang sound(my truck did it too) I discovered by talking to Jerry Lemond one day is likely due to the spline on the output shaft being dry. Jerry suggested in my case to pull the driveshaft out and grease the inside spline of the slip yoke, then put it back on.

If your u-joints are bad, you'll need to pull it out anyway to replace them

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby puttputtinpup » Sun Sep 08, 2019 8:53 pm

Yes, i did what Jerry suggested and it fixed the popping clang when taking off from a dead stop especially just after having used reverse.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Sun Sep 08, 2019 11:56 pm

Andy, thanks a lot for your advice. Got worse tonight and I'm away from home base at the moment without a jack ( :( ), so will have to take this in to the shop. Going nice and slow - otherwise it gets really noisy.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby puttputtinpup » Mon Sep 09, 2019 5:39 am

Changing u-joints on a pup was my least favorite job to do on a pup.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Mon Sep 09, 2019 5:00 pm

Got the diagnostic - rear u-joint was really loose, the front was fairly loose. Driveline's out right now and at a shop to be reconditioned; should be back in tomorrow.

However the mechanic told me that the rear differential pinion bearing is going out and needs to be replaced. Is this a part that can be obtained "universally", or something specific to my P'up rear end that I need to order from Jerry Lemond? I believe I have the 3.42 rear end (truck goes 85 mph on the freeway in 4th...there was also a 3.73 if I remember correctly?) - will know tomorrow if this is something the shop can source, including the shims to do it right.

At this point in time, I need the truck to get back to home base and for daily errands - I'll probably drive the truck with the old pinion bearing and new u-joints while I can make sure the diff rebuild can be done properly. If any of you have experience with this, please let me know. Thanks in advance.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Halden » Mon Sep 09, 2019 9:27 pm

4 speed gas pots have the 3.42. 3.73 only came in the diesel 5 speeds.

Those bearings should be universally obtainable. Bearings and shims are pretty much just...Well...Bearings and shims...for the most part. You could take it to an axle shop and they can source just about anything you need.
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Mon Sep 09, 2019 9:51 pm

Halden wrote:4 speed gas pots have the 3.42. 3.73 only came in the diesel 5 speeds.

Those bearings should be universally obtainable. Bearings and shims are pretty much just...Well...Bearings and shims...for the most part. You could take it to an axle shop and they can source just about anything you need.


Halden, great to hear from you and thanks for your words. I figured they'd be universally obtainable, though it appears this'll be a big job. My dad told me that the entire axle would have to be removed and such to get to it. I'm not knowledgeable in this area.

I don't think the raspy noise was coming from the rear end though (hopefully just u-joints), so if it becomes a major operation, I may let it wait. It will get done eventually though.

*Edit: To add, my dad wants me to source the necessary parts before the work begins to save money on the parts. I searched RockAuto under '86 P'up 1.9L but the search yielded multiple variations for the diff pinion bearing...if any of you have parts numbers handy, I could save a lot of downtime at the shop for an "order upon visual inspection" scheme.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby puttputtinpup » Tue Sep 10, 2019 12:01 am

Um... if the pinion yoke is a bit loose, it's not a huge cause for alarm. Double-check your mechanic's diagnosis. I've seen several of the pups (2 of them my own) rear pinion nut get loose and fixing it is just a matter of carefully tightening the big nut back up inside the pinion yoke. It'll have to be tighten to a reasonable amount of torque. Check with Paul in this. He'll know about how tight to set it. There's a crush sleeve or something in there and can't get it tighter than it was originally set to.

I wouldn't go through changing bearings and all that if it wasn't necessary

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Tue Sep 10, 2019 12:25 pm

Andy, thanks a lot for your reply. This is very helpful. I'm not sure who Paul is, but is he reachable from the forums? The driveline should be back earliest by later today, and it'll be a matter of mounting it on the lift to be back on the road again.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Halden » Tue Sep 10, 2019 3:24 pm

Here are some part numbers from 87. They should be interchangeable from 86. I would check out what Andy said. It's very possible that's all you'll need to do. seems to be a somewhat common issue that goes misdiagnosed.

I should also add whenever a rear end is failing or something isn't right you'll generally hear humming and whirring. Something along those lines. Your symptoms were classic u joints.
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It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"
83 LS Long Bed Diesel 4x4
82 LUV Short Bed Diesel 5 Speed 2wd
64 Chevy C20 w/ 283 & 4 speed.
05 Sonata with a standard

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Isuzu Faster
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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Wed Sep 11, 2019 1:07 am

Halden, thanks a lot for these - will reference for future repairs. The driveline shop installed new u-joints, bead blasted, and repainted the entire driveline - looked brand new! Upon installing, the mechanic told me that the pinion yoke play was about 1/8", and was surprised I didn't hear the rear end while driving (I've never heard anything out of the ordinary). Since I didn't have the torque specifications, I didn't mention tightening the nut to him and left it alone.

Test driving yielded 'A-OK' operation with no noises whatsoever. I also drove over a stretch of newly paved pristine road and kicked it into Neutral around 40 mph to check for any hums from the rear end - no hum whatsoever. Most of my driving is done locally, so hopefully it'll stay this way.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby puttputtinpup » Wed Sep 11, 2019 8:51 am

Glad to hear it turned out okay. Keep an eye on that pinion yoke for a leaky seal. My son's LUV had a bad seal. The Chevy dealer where he worked after school took that nut off, replaced the seal, and reinstalled the yoke. I don't know how tight they put the nut on but it was fine. I'm thinking about 70-100 ft lbs. Paul would know

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Re: Raspy Scratching Noise Periodically on Acceleration

Postby oldestisuzuist » Wed Sep 11, 2019 9:35 am

Quote: "Since I didn't have the torque specifications, I didn't mention tightening the nut to him and left it alone."
There are no torque specs for tightening the pinion nut on a fully assembled unit. Any torque specs you can find are for initially installing only the pinion into a bare housing, there will be a very high first torque- 200+ ft-lbs- for collapsing the crush sleeve, then a second lower reading to set the bearing preload. The preload is set while rotating the pinion flange at a certain measured rotational force applied with a fish scale. This measured rotational force does not take into account any added drag from the differential or ring gear, thus the rotational force & pinion torque reading should be different for a fully assembled unit. These different torque readings don't exist. When a pinion nut gets loose enough it will start to cause noise, usually a howl or whine when coasting in gear that gets worse over time, finally starting to clunk. I have had success gradually tightening the nut, then test driving, until the noise disappears, then staking the nut to keep it from backing off again. If you overtighten you will ruin the bearing.
There needs to be a bit of play at the pinion yoke just as with a front wheel bearing. As long as the play is sideways & not in & out I wouldn't worry too much until you start to hear noise. Pinion yoke play can lead to seal failure, so keep a close watch for that.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
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Re: Raspy Scratching Noise Periodically on Acceleration

Postby Isuzu Faster » Wed Sep 11, 2019 9:01 pm

Andy and Paul, thank you so much for your advice. I really appreciate all of your help and am heavily indebted to you all here. It probably was a good thing I didn't have the mechanic put his weight on that pinion nut to tighten it up. Will keep an eye on the rear end - as of now there are no leaks, and as far as the mechanic told me, the play was sideways and not in-and-out.

On another note, there is no more "clang" upon starting from a stop - those splines were greased upon reassembly, so that likely took care of that. I really baby this truck (no hard shifts, burn-outs, or jumps across intersections), so I'll continue to strive to preserve what I have.
~ Cheers, Steve.

1986 Isuzu P'up (Faster 2WD), 1.9L G200Z Gasoline, 4-spd, Beige Amino-Alkyd Enamel.

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