gear Chattering/rattling noise in my cj7 when coasting down the road

[ericksin]

I have had this noise for a while and its getting louder. at higher speeds the noise gets louder, I have installed an 727automatic Transmission and 8.8 rear axel (not for this reason, they where upgrades) still had the same noise, got a little louder with the rear upgrade, I had installed the gear before install so I thought maybe I did something wrong. so opened and checked everything and all the clearances checked out to be ok. I installed a new drive line (due to braking mine on a trail) and the noise got much louder! swapped it with a different one and got the same noise. 2 weeks ago I installed a 4:1 in my Dana 300 Transfer Case , the kit didn't come with bearings but they looked fine to me, I installed every thing to specs but still have the noise, the old gears that came out of my Transfer Case looked great, before I did the 4:1 upgrade the rear Transfer Case pinion shaft was loos, the kit came with shims and now everything is tight. at speed over 50 it sounds like something is going to blow up when im costing. my dad is starting to have the same problem, he has a 4 speed trany, Dana 300 & AMC20 in the rear

what do you thing it is??? can bearings be bad and look fine?

 

[tarry99]

I have had this noise for a while and its getting louder. at higher speeds the noise gets louder, I have installed an 727automatic transmission and 8.8 rear axel (not for this reason, they where upgrades) still had the same noise, got a little louder with the rear upgrade, I had installed the gear before install so I thought maybe I did something wrong. so opened and checked everything and all the clearances checked out to be ok. I installed a new drive line (due to braking mine on a trail) and the noise got much louder! swapped it with a different one and got the same noise. 2 weeks ago I installed a 4:1 in my Dana300 transfer case, the kit didn't come with bearings but they looked fine to me, I installed every thing to specs but still have the noise, the old gears that came out of my T-case looked great, before I did the 4:1 upgrade the rear t-case pinion shaft was loos, the kit came with shims and now everything is tight. at speed over 50 it sounds like something is going to blow up when im costing. my dad is starting to have the same problem, he has a 4 speed trany, Dana300 & amc 20 in the rear

what do you thing it is??? can bearings be bad and look fine?

Noise and vibration will travel up and down the length of your Jeep and in and out of every component.........tough to find sometimes.....Coasting clearance in gears can be an issue as can be the change in drive line angles when doing so. I would check these angles out along with the U-joints on both front & rear drive lines......you said you changed the rear to an 8.8 , that would be a good place to start. Tom Woods Drive line on line has some info that may be helpful.

 

[ericksin]

Noise and vibration will travel up and down the length of your Jeep and in and out of every component.........tough to find sometimes.....Coasting clearance in gears can be an issue as can be the change in drive line angles when doing so. I would check these angles out along with the U-joints on both front & rear drive lines......you said you changed the rear to an 8.8 , that would be a good place to start. Tom Woods Drive line on line has some info that may be helpful.

I just change the u-joint yesterday, the angle of the axel is good but coming from the Transfer Case naaaa... I wish it was better. I droped the Transfer Case some but you can only go so far before the motor hits the fire wall and the fan starts hitting the showed. when I went back in to my 8.8 my pinion was a little towards the heal, so I adjusted my ring gear closer and got it damn near perfect. I did notice the area around my pinion get really hot to the touch, the back of the axle not so much, what do you think about that, is that normal?

I will check out Tom Woods Drive line

 

[tarry99]

I just change the u-joint yesterday, the angle of the axel is good but coming from the T-case naaaa... I wish it was better. I droped the T-case some but you can only go so far before the motor hits the fire wall and the fan starts hitting the showed. when I went back in to my 8.8 my pinion was a little towards the heal, so I adjusted my ring gear closer and got it damn near perfect. I did notice the area around my pinion get really hot to the touch, the back of the axle not so much, what do you think about that, is that normal?

I will check out Tom Woods Drive line

Hot Pinion......depends on too many things that are not addressed here. How long is your rear shaft? Ever think about a double Cardan Joint? Even though Bearings may look fine ....that can change under magnification , Once bearings get a wear pattern in them that creates noise there is no getting better. At some point you may need to change those in your Transfer Case . But I would address that rear drive line angle first..........Have you tried any wedges between the housing and spring?

 

[ericksin]

Hot Pinion......depends on too many things that are not addressed here. How long is your rear shaft? Ever think about a double Cardan Joint? Even though Bearings may look fine ....that can change under magnification , Once bearings get a wear pattern in them that creates noise there is no getting better. At some point you may need to change those in your Transfer case. But I would address that rear drive line angle first..........Have you tried any wedges between the housing and spring?

I used to have a double u-joint drive line but it broke a didn't have the money to buy another one, so I slapped some new u-joints on this one and there she goes. the drive line is about 27'' long.... I attach 2 picks of my drive line angle, hope they come through

 

[ericksin]

I got a question I just noticed while I was putting in some old 3 degree shims I had laying around. would a off balance drive line cause that kind of noise?

My last drive line was in bad shape, the spline was so warn out and probably stretch that you can grab the center and move it side to side a lot, the shaft I have on now the spline is tight but I don't see any weights on it, I had that laying around for a long time, it looked like someone shortened it at one time. I through new u-joints on it and installed it on my jeep, what do you think?

 

[73CJ]

Oh My!

There's a reason it had a double cardigan joint at the Transfer Case . The pinion of the rear is pointed at the Transfer Case as it should with the DC shaft

Look at Tom Woods driveshafts and do it right. Better check the rear gears while you're at it

Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist

 

[tarry99]

I got a question I just noticed while I was putting in some old 3 degree shims I had laying around. would a off balance drive line cause that kind of noise?

My last drive line was in bad shape, the spline was so warn out and probably stretch that you can grab the center and move it side to side a lot, the shaft I have on now the spline is tight but I don't see any weights on it, I had that laying around for a long time, it looked like someone shortened it at one time. I through new u-joints on it and installed it on my jeep, what do you think?

A drive line that is either not phased correctly, not balanced, or the angles are out of whack will cause all of the above............Like I've mentioned before go to Tom Woods drive line and educate yourself.

 

[ericksin]

No more noise!!!!!!!!!!!

I found a new end for my CV drive line, took it for a test run and so far so good.

I did go to Tom Woods drive line and educated my self, had to read it a few times but I got it