Gear swap - Engine Whining

cthomas31

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Hey guys,

I'm running 35s with 2.5 inch lift on my JLU sport and was losing my 7th and 8th gear on the highway so decided to switch to 4.56 gears. After I got the Jeep back from the shop, I noticed a "whining" noise at certain RPMs/speed. I put 500 miles on it and took it back to the shop so they could do the 500 mile inspection and change out the diff fluid. The shop said everything looked perfect and that the whine does not have anything to do with the new gears.

So here's my question. What is the whining noise I'm hearing? Here's some troubleshooting and information about the whining and when it occurs.

If I am in neutral and/or park, the whining noise does not happen (even if I hit the gas and raise RPMs)
When I'm in drive, the whining noise does not always occur. It only happens at specific speeds. For instance, if I'm going 45 mph in 8 gear there's no noise, but when I am going ~48mph I can hear the whining.

I just took a $2k mile roadtrip and had no issues with the Jeep other than hearing the noise at certain speeds.

Hopefully you guys can help diagnose. Any information is helpful!





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Headbarcode

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Hey guys,

I'm running 35s with 2.5 inch lift on my JLU sport and was losing my 7th and 8th gear on the highway so decided to switch to 4.56 gears. After I got the Jeep back from the shop, I noticed a "whining" noise at certain RPMs/speed. I put 500 miles on it and took it back to the shop so they could do the 500 mile inspection and change out the diff fluid. The shop said everything looked perfect and that the whine does not have anything to do with the new gears.

So here's my question. What is the whining noise I'm hearing? Here's some troubleshooting and information about the whining and when it occurs.

If I am in neutral and/or park, the whining noise does not happen (even if I hit the gas and raise RPMs)
When I'm in drive, the whining noise does not always occur. It only happens at specific speeds. For instance, if I'm going 45 mph in 8 gear there's no noise, but when I am going ~48mph I can hear the whining.

I just took a $2k mile roadtrip and had no issues with the Jeep other than hearing the noise at certain speeds.

Hopefully you guys can help diagnose. Any information is helpful!
First off, did you reprogram for the increased tire diameter. Thats one of the several pieces of data that the 8-speed auto uses to adjust its shift points. If that's off, so will the shift points, resulting in the loss of the higher gears and overall non optimal drive ability. I've got 38's, and reprogrammed with a tazer, and stock Rubi gears. Hits 8th all the time, and a regear isn't even on the radar.

Second, if the whining sound wasn't there before the gear swap, than its possible that the shimming wasn't done as accurate as it should've been. What you're hearing is the gear mesh. You should get a second reputable shops opinion.
 
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cthomas31

cthomas31

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First off, did you reprogram for the increased tire diameter. Thats one of the several pieces of data that the 8-speed auto uses to adjust its shift points. If that's off, so will the shift points, resulting in the loss of the higher gears and overall non optimal drive ability. I've got 38's, and reprogrammed with a tazer, and stock Rubi gears. Hits 8th all the time, and a regear isn't even on the radar.

Second, if the whining sound wasn't there before the gear swap, than its possible that the shimming wasn't done as accurate as it should've been. What you're hearing is the gear mesh. You should get a second reputable shops opinion.
Yeah I reprogrammed for the 35s but never hit 8th gear on the highway. May be because the Sport has 3.73 gears and the Rubi has 4.10s. Thanks for the comment. I will probably take it to another shop and get a second opinion.
 

Headbarcode

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Yeah I reprogrammed for the 35s but never hit 8th gear on the highway. May be because the Sport has 3.73 gears and the Rubi has 4.10s. Thanks for the comment. I will probably take it to another shop and get a second opinion.
Did you program the actual diameter, or the size on the sidewall? The former is the way to go.

You should have 3.45 gears, unless you have the diesel. Yeah, I've got shorter gears to begin with, but I made a larger jump in size difference from factory.

But, its a moot point because you already did the swap. Other than the intermittent whine, how is the overall drive ability compared to before the 4.56's?
 

deserteagle56

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The whine you are hearing has EVERYTHING to do with the newly installed gears. Happened to me when my rig was regeared.
 

JimLee

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You can also reprogram the gearing in the computer, at least you can with the flashcal, i think this is just as important as tire size for the transmission if not more so.
 
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cthomas31

cthomas31

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The whine you are hearing has EVERYTHING to do with the newly installed gears. Happened to me when my rig was regeared.
What did you end up doing to fix the issue? I scheduled an appointment with my local dearlership to get a diagnosis and see if they can fix.
 

Paluss

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it may be the gear type they used, straight cut gears naturally create a hell of a lot of noise; helical gears mesh together in small segments at a time while straight-cut teeth are in contact with each other fully and for a longer period of time which makes for a very distinctive whine.
 

Oldbear

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If it wasn’t there before it’s gotta be the new gears. As noted, straight cuts are noisy, but I believe I’d get it checked but a competent mechanic. If the gears are not setup right they WILL whine ( and also wear much quicker than they should).
 
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cthomas31

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Did you program the actual diameter, or the size on the sidewall? The former is the way to go.

You should have 3.45 gears, unless you have the diesel. Yeah, I've got shorter gears to begin with, but I made a larger jump in size difference from factory.

But, its a moot point because you already did the swap. Other than the intermittent whine, how is the overall drive ability compared to before the 4.56's?
Yep I measured the actual diameter.
 

Paluss

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If it wasn’t there before it’s gotta be the new gears. As noted, straight cuts are noisy, but I believe I’d get it checked but a competent mechanic. If the gears are not setup right they WILL whine ( and also wear much quicker than they should).
I agree, if the gears are meshed to close together that could cause the whine noise too. On the plus side straight cut gears are much stronger then helical gears...
 

aro

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The whining is definitely from the new gears. It's pretty rare in the Jeep world, but in the Tacoma world it's relatively common.

The mechanic that regeared my Tacoma warned me about it beforehand, but I was lucky and didn't get the whine. He's specialized in regearing all sorts of vehicles for many shops in SoCal, so he knows a thing or two about it.

The bad news: it's annoying and I am not aware of any fix
The good news: it's harmless

You should have it checked out anyway if you can, make sure it's not some obvious mechanical failure.
 

2Wheel-Lee

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The shop is brushing you off for their poor workmanship. Simply looking at the gears, they won't see the cause of the whine. They screwed up the install.
 

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