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Clank or knock when shifting into reverse

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Old 05-02-2012, 12:33 AM   #1
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Clank or knock when shifting into reverse

Hey everyone. Every now and then (but often) I keep hearing a clank or knock noise coming from under the truck when I shift the truck into reverse. It has done it since I got this car, but I am hearing it more and more when I shift the car into reverse, especially if I was just moving forward. This happens in 2 or 4 wheel drive (more so in low range). I don't know the condition of the U-Joints, but I just had the rear pinion seal replaced a few months ago and they found no issues with it and I saw them checking it. I had the differential fluid changed before Christmas and they found nothing out of the ordinary (just some fine metal on the magnet and they said it was nothing to worry about). This is exactly why I try to avoid backing this truck up, but could I have a transmission that is on it's way out or some other damage? I have almost 118k on it. I change fluids every year, I don't abuse it and I have a cooler for the trans.
Old 05-02-2012, 12:40 AM   #2
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Re: Clank or knock when shifting into reverse

U joint.
Old 05-02-2012, 01:05 AM   #3
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Re: Clank or knock when shifting into reverse

Quote: Originally Posted by 90blueS10
U joint.
But only when going into reverse?

Also, could that account for a knock when I really hit the gas?

How bad of a repair is that?
Old 05-02-2012, 01:07 AM   #4
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Re: Clank or knock when shifting into reverse

not terrible.
Old 05-02-2012, 01:13 AM   #5
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Re: Clank or knock when shifting into reverse

Quote: Originally Posted by 90blueS10
not terrible.
How do I know which one to order? I keep finding several different types. The obvious difference would be ZR2 vs non-ZR2 and that is easy, but I am also finding ones that are Sport option vs non-Sport option and greasable vs non-greasable?
Old 05-02-2012, 01:14 AM   #6
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Re: Clank or knock when shifting into reverse

greasable means it has a grease zerk, non-greasable is just a sealed unit.

as far as sport and non sport i have no idea.
Old 05-06-2012, 12:13 AM   #7
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Re: Clank or knock when shifting into reverse

mine does this too in reverse only. i narrowed it down to play in the rear end and the trans its self. jack your rear up and put it in nuetral and spin the driveshaft *kinda jerking it when changing direction see if it makes the same sound
Old 05-06-2012, 04:26 PM   #8
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Re: Clank or knock when shifting into reverse

Quote: Originally Posted by Jaewolf
mine does this too in reverse only. i narrowed it down to play in the rear end and the trans its self. jack your rear up and put it in nuetral and spin the driveshaft *kinda jerking it when changing direction see if it makes the same sound
What does that mean if it is the same sound? Bad repairs are in order or leave it?

Also, if it is the tranny, could it be an overfill? I checked the dipstick and I noticed that it is above the hot mark by about 1/2" when it is warm and at the top of the hot mark when it is cold. I may have overfilled it a couple months ago when I changed the fluid (It was on ramps when I did it and I didn't want to start it if it was low), but it has been driving fine. If it really was overfilled, wouldn't it just come out the overflow?

In terms of the rear end, I had the fluid changed and they looked at the magnet and it was a "normal" amount of metal and nothing to worry about. I just had the pinion seal replaced a few months ago and they checked for play in the bearings and the only real problems were blocked vents, which they fixed.
Old 05-06-2012, 05:58 PM   #9
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Re: Clank or knock when shifting into reverse

When I said trans I ment to say transfer case. My sound didn't start until I bumped up my trans pressure for firming shifts. The t case makes the sound on mine. The sound I mean is the clank or knock you hear when putting it in reverse. When u hear it are you completely stopped, slowly moving in same or other direction. Etc reason I say if you are slowly moving the computer firms the shift to prevent slipping. Over filling a little shouldn't effect it.
Old 05-06-2012, 06:40 PM   #10
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Re: Clank or knock when shifting into reverse

Quote: Originally Posted by Jaewolf
When I said trans I ment to say transfer case. My sound didn't start until I bumped up my trans pressure for firming shifts. The t case makes the sound on mine. The sound I mean is the clank or knock you hear when putting it in reverse. When u hear it are you completely stopped, slowly moving in same or other direction. Etc reason I say if you are slowly moving the computer firms the shift to prevent slipping. Over filling a little shouldn't effect it.
My truck is completely stock except for the mods below.

I completely stop and wait a couple seconds before I touch the shift lever unless it is into 3, 2 or 1. Only people who shift while the truck is moving would be mechanics, but only the less careful ones do that.
Old 05-15-2012, 07:17 PM   #11
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Re: Clank or knock when shifting into reverse

U-Joints are tight and axle is okay. Had it checked. So the problem is elsewhere
Old 05-21-2012, 01:41 AM   #12
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Re: Clank or knock when shifting into reverse

My underneath makes the same sound, ive began pressing my U joints out anyway as they are stock (Sealed and injected with hard plastic around the caps), while i wait to get my engine pieces back from the machineshop (doing a engine rebuild). Ive done the above mentioned method trying to torque the shaft left and right under the vehicle with no results. I did notice however the worrying pitch black color of the grease in the needle bearing caps. They also had wear in the cap walls. Ive only gotten one u joint out, and in the process cracked my fathers bench vise. Il see what the others look like inside when the press gets here this week. As far as your noise it could be a failing center driveshaft carrier bearing?!? not 100% sure on that but i would check their.
Old 05-21-2012, 02:23 AM   #13
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Re: Clank or knock when shifting into reverse

First, let me say, a little bit of 'back-lash' is normal in aged vehicles. This is a combination of the splines in the output shaft and axle shafts plus the spider gears in the differential. All of which just showing normal wear. My 2005 does it and pretty much every rear wheel drive vehicle I've owned has made this noise. The one way to soften the clunk is to pull the rear drive shaft and put some grease on the splines, but don't pack it full, that will create a hydraulic effect and could cause damage, just coat the splines and see if that makes a difference.
Old 05-21-2012, 02:26 AM   #14
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Re: Clank or knock when shifting into reverse

Quote: Originally Posted by ComputernerdBD
U-Joints are tight and axle is okay. Had it checked. So the problem is elsewhere
Oh and just a word of advice, not every mechanic is going to be spot on. That is if you had a mechanic check. Anyways you wont truly know unless you see for yourself and have it apart. Before i took my driveshaft down everything was tight and appeared good, judging from me trying to torque it left and right with no noise. Even when i had it completly out, the connections when moving them back and forth on the u joint were fine no squeaks. U joints are relativly cheap i would just say go ahead and get'em switched, especially if they look old or rusty.
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