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Rearend Noises

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Red20 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Topic: Rearend Noises
    Posted: Apr/22/2017 at 1:07am
I'll be pulling apart the factory model 20 in my 1969 AMC Javelin tomorrow to diagnose some issues, but in the meantime, hopefully someone can give me some insight on what I might be looking at.

So, on deceleration from about 40mph down, I'm hearing a fast clicking sound. If I apply a little torque it goes away. I can get on and off the gas and hearing it clearly starting and stopping. It might do it a little more when warmed up. Not sure. If I give it a little gas while on the brakes decelerating, it doesn't do it.

There may also be little bit of a whirring noise at 40mph+. Also, there's a slight vibration from about 80mph that increases slightly up to about 120mph. My pinion angle is a bit off and my driveshaft is a good inch shorter than I'd like. That could be contributing.

I don't really have the money to spend, but there's a nice powder coated Ford 8" housing for sale locally that's 57" WMS to WMS with 43" perch width. Has new end bearings pressed in and axle shafts. $780. Another guy has a nice looking Ford 3rd member built with 3.00 gears (currently running 2.87) for only $150. It's an open differential.

That would be a nifty swap, and something I could do this weekend as long as I can get brake parts.
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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mixed up View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mixed up Quote  Post ReplyReply Direct Link To This Post Posted: Apr/22/2017 at 8:36am
the 8 inch is a good idea but have you thought about a 8.8 swap might be cheaper in the long run and you can get them real cheap with disc brakes at local junk yard from explorers about 150-200$ and lots of parts available for them at swap meets
69 amx 290 auto
65 220 290 4spd
80 ford fairmont
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/22/2017 at 8:57am
Yeah, I've thought about an 8.8 for a while. I'd need to shorten the long side and get another short side axle shaft.
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Red20 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2017 at 11:59pm
Found another 8" for only $350. Came out of a Falcon and is 58" wide WMS to WMS. Spring perch spacing is like 38-1/2" though. It's complete with a center section with 3.00:1 gears. I'm running 2.87 now and am not upgrading to an overdrive just yet. Also has brakes and e-brake cable in very good condition. I really like the idea of a removable third member and the ability to set it up on the bench and then bolt it into the car. At least I think I do. I've never had one. I've only ever had Dana 30/35/44/60, AMC Model 20, and GM 12 bolt rear ends.

I can get that one, which apparently has newer end bearings and setup my pinion angle then weld new perches. Or I can get a drum brake 8.8 for $150 I was looking at, shorten it and get a second short side axle. It's a 3.73 w/posi. I won't be doing over 55mph commuting anymore unless I find another set of gears. All in all, I'll be out about the same $$$ probably after fresh brakes and whatever else they need.

The 8.8 is a little stronger axle and can be built beefier in the future than the 8" can with c-clip eliminator and a few other parts. Lockers and limited slip parts are cheaper too. The 8" axles are only 28 spline but at least don't rely on c-clips. I'm not likely to be running big slicks and don't plan to see much more than 450hp/tq at any point. I'm around 375hp/410tq now and likely will only be doing a cam swap and better flowing exhaust.

1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RTTComanche17 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2017 at 10:49am
Originally posted by Red20 Red20 wrote:

I'll be pulling apart the factory model 20 in my 1969 AMC Javelin tomorrow to diagnose some issues, but in the meantime, hopefully someone can give me some insight on what I might be looking at.

So, on deceleration from about 40mph down, I'm hearing a fast clicking sound. If I apply a little torque it goes away. I can get on and off the gas and hearing it clearly starting and stopping. It might do it a little more when warmed up. Not sure. If I give it a little gas while on the brakes decelerating, it doesn't do it.

There may also be little bit of a whirring noise at 40mph+. Also, there's a slight vibration from about 80mph that increases slightly up to about 120mph. My pinion angle is a bit off and my driveshaft is a good inch shorter than I'd like. That could be contributing.

Red,

Is the fast clicking sound tied to engine speed or to wheel speed? If tied to wheel speed, it might be something to do with the drive shaft especially since you described a vibration/noise at 3 equally spaced speed intervals (imbalanced rotating things tend to have different vibration modes at multiples of natural frequency). 

Also of note, I had a similar fast clicking sound during deceleration but not during acceleration (but mine was present no matter what speed i was going). It turned out that my driveshaft u-joint was contacting a bent heat shield. Basically under load (acceleration), the torque forces your pinion down toward the ground, pulling the driveshaft away from whatever it may be hitting. During coasting, it relaxes and pinion rotates up toward the bottom of the car, bringing the driveshaft closer to whatever sheetmetal is above it. But again, would be a weird coincidence if this was the case.

It could also be a flat needle bearing in your u-joint. The reason u-joints need a bit of angle when installed is because without this angle, the needle would never rotate in the bearing cups on the u-joint -basically they would cease to be a bearing. Under acceleration, when everything moves around under load, the goal is zero angle at the u-joints as this provides for the most efficient power transfer. Consequently, the needle bearings are not rotating during this brief period.  So if it is a wiped needle, no rotation means no ticking noise (under acceleration) and rotation means a tick every time the flat portion of the needle rotates past the load bearing surface. 

So my thought would be to check the driveshaft, u-joints, and things causing clearance issues first (bad rubber mount, bent sheet metal, etc). If everything looks good then maybe it is the rear end. And again this all assumes it is a wheel speed tick, not an engine speed tick. 

Just my $0.02
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2017 at 4:38pm
Thanks for the reply. I'm not getting the clicking sound at all now. It's a vibration and a subtle grinding noise that I can feel and just barely seem to hear. Accelerating from about 20mph up to 50mph seems to be the worst. Steady cruise around 65mph isn't too bad but slightly noticeable. Granted my exhaust is loud, so it's hard to diagnose anything by ear.

I have been busy at work, so I haven't had the drive shaft off to pull u-joint caps or pulled apart the rear end yet. I did put the trans in neutral and turn the driveshaft back and forth and there doesn't "seem" to be excessive backlash from wear. And the u-joints aren't shot to the point there is any slop at all. They feel tight at least.

I think if the ring and pinion and bearings look ok and the u-joints check out, I'm gonna drop the rear and drill offset holes in my perches to move the axle forward a little to get the slip yoke in a little more. Then I'll find a flat piece of ground and measure my driveline angles. I have a set of aluminum shims I can use and adjustable rear shackles. I should be able to get the driveline angles right. I can shim my transmission crossmember too if I need to drop the output shaft.

Hopefully I'll find the culprit(s) though and determine how to proceed. I kind of hope the housing is somehow shot so I HAVE to swap rearends. I don't necessarily want to spend the money, but I've got my eye on a few rearends on Craigslist.
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2017 at 4:41pm
Forgot to mention, all of my mounts are nearly new - all suspension, transmission, engine.
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2017 at 8:22am
You probably have a wheel bearing going out. The outer bearings take all the load, and the right one more than others. Just make sure you get those hubs torqued back to 250 ft/lbs if you take them off to replace bearings.

How do you use this car? The Ford 8" is a good axle for cruising and just an occasional trip down the drag strip, especially with a mild engine. Weighs a lot less than the 8.8" or other heavy axles, probably about the same as the AMC 20... maybe a little less. So if this is just a stock cruiser, the lighter axle would be great, and the 3.00 gears are close enough to 2.87 you won't notice much difference in take-off or cruising speeds.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RTTComanche17 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2017 at 10:10am
Yeah, if there is no clicking noise, then I'd tend to agree with farna. Subtle grinding would lead me to look at bearings. Even bearings that are designed for "infinite life" - ha - will go eventually as seals degrade and grit gets in or when power levels are increased above design specs. 

One other thing to check when light grinding noises are apparent, is for a sticky wheel cylinder. Might be a dragging brake shoe - they can make light grinding noises - but that generally manifests itself with grinding and making the car pull left or right which you haven't mentioned.

You sound like someone who is fairly on top of things, but i like to check the easy things first. Side story - had a friend in high school with a mystery ticking noise coming from the back of his car. He parked the car and bought a rebuild kit for his rear end, got under the car and found a zip tie around his driveshaft. Never bothered to check anything before buying parts, HA! We haven't let him forget about it either...

But, if you are hoping something is wrong so you HAVE to get a new rear end, I'd just mentally convince yourself that the grinding is a pinion bearing and the mysterious ticking is a chipped/cracked pinion tooth...."but honey, it could explode an leave us stranded in the middle of nowhere! I have to fix it!" -honey could refer to a wife or wallet... your choice...


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2017 at 10:42am
I use the car as a nearly daily driver with occasional runs down the drag strip. It's a fairly mild build with about 370hp/410tq. I was thinking maybe wheel bearing myself or carrier side bearing even. It does have that vibration with acceleration but when you let off the gas it smooths out until you get back on it.

I've done the zip tie on the driveshaft prank to people many times. That's a good one.

Bottom line is, I need time to get it home and look over everything. Then I can figure it out, hopefully.
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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