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01dakota_355
Dodge Dakota
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12/30/2004
10:44:21
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 Subject: Rear end hopping problem - stumper...
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I have a 2001 CC 4.7 auto 4x4, and I have the dreaded rear end hop when braking that has been well documented on this board. I'm going crazy trying to figure out what's wrong.
Here's what I've done: replaced the rear brake shoes (2x), replaced rear drums (3x), flushed brake fluid, checked shocks, checked sway bar, checked axle seals, adjusted rear brakes, check brake springs, hardware, checked u-joints, checked driveshaft for balance, etc.
I've pretty much ruled out the rear brakes. But the odd thing is that it only hops from 42-37mph while braking, no matter what I do, and it doesn't always do it. The truck has 47,000 miles on it. Could it be the rear axle ABS sensor is going haywire? There has been no ABS light on in the dash (it works), no check engine light (also works), and the speedometer has been fine.
Any ideas? Thanks in advance!
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RadioMan
Dodge Dakota
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12/30/2004
13:25:42
|  RE: Rear end hopping problem - stumper...
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01dakota_355, this very same problem has also got
me stumped on a 79 AMC Concord I replaced the rear
shoes during this past summer. Everything was just
fine untill I had the rear drums turned and
replaced the shoes. The old shoes were not even
cutting into the drums yet but I thought I'd
do the job before it does.
I also asked a lot of questions to different guys
in my area and they didn't have a good fix for it.
I ended up backing the shoes off to the point that
the front disc's did 90% of the braking. That
helped a bunch but I'm still stumped.
I grew up replacing drum brakes and have NEVER
ran into this problem before.
I want to see the advice any others have about
this...
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Silver
Dodge Dakota
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12/30/2004
14:11:58
|  RE: Rear end hopping problem - stumper...
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Have you checked the proportioning valve?
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blakels
Dodge Dakota
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12/30/2004
15:29:35
| RE: Rear end hopping problem - stumper...
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Check parking brake cables for adjustment and/or binding especially if they are rarely used. These things can be very intermittant and can cause severe sudden vibrations. Even at highway speeds without applying the brakes if they're hanging up.
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fastdak
Dodge Dakota
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12/30/2004
23:04:54
| RE: Rear end hopping problem - stumper...
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check to see if the drums are out of round. that's what happened to mine. the dealer re did my drums. the prob. went away for a little while. maybe some thicker after-market drums will fix it.
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GraphiteDak
GenIII
12/30/2004
23:22:55
| RE: Rear end hopping problem - stumper...
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When I saw this thread I thought it was going to be about wheel hopping when doing a burnout :-)
After reading this, I'm glad mine came with those huge Disc brakes on the back.
Maybe there is a swap for Disc into yours?
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try this
Dodge Dakota
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12/31/2004
02:49:14
| RE: Rear end hopping problem - stumper...
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Message:
sounds like you have cash to burn, change the rear shocks.
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01dakota_355
Dodge Dakota
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12/31/2004
11:57:11
| RE: Rear end hopping problem - stumper...
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Thanks for all the advice...the rear drums were checked (the last two sets) by a machine shop before I put them on, so I don't think that's the problem. Besides, I can't believe that three different sets of drums would all be bad.
Silver- do you think the proportioning valve could be sending too much fluid to the back? If that were the case, would it throw the brake light (in the dash) on?
I don't have cash to burn- the drums are Napa lifetime warrantied (one time expense), and the shoes were about $35. I just don't want to start replacing parts that aren't causing the problem... If I knew rear discs would solve the problem, I'd do it in a heartbeat- that would be cash well spent. That's why I'm considering an 03 or 04.
Incidentally, though, does anyone know how long the stock shocks should last on this vehicle? They have no leaks, and though they look to be in good shape, I know this is not a good indicator of internal condition. I disconnected the bottom of each shock and pushed them up - no flat/dead spots, good resistance, and both "returned" fairly quickly. As far as replacements, has anyone used the Monroe Sensatracs? Are they any good?
Thanks again!
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Butch
Dodge Dakota
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12/31/2004
22:59:25
| RE: Rear end hopping problem - stumper...
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I replaced the shocks on my 01 at 15000 miles. Original equipment shocks are crap. I put Monroe Reflex's on and have been very happy with them.
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Jag
Dodge Dakota
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1/02/2005
16:34:33
| RE: Rear end hopping problem - stumper...
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01Dak
Could you explain what you mean by wheel hop. Does the tires momentarily lock up? Do you get a visible bed hop as well?
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01dakota_355
Dodge Dakota
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1/02/2005
21:46:28
| RE: Rear end hopping problem - stumper...
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Jag-
It's not really a wheel hop, I think it's more in the suspension...like a bounce. When I am braking, going from ~44 down to ~37, you can feel a bounce (or shake) in the rear of the truck. It seems the bed is hopping too, but it's easier to feel the bounce than to see it. I don't think the tires lock up, because there's never any skidding. When the truck slows down (coasts) without braking, it never bounces.
Tonight I drove along about 50-55, and used the parking brake (while holding the release) to slow down several times. Now, the bounce was gone; no pulsing felt, so I know the drums can't be warped (that, and they only have about 300 miles on them).
The other night I found some ice to test the rear ABS. Only once could I get them to activate (heard the ABS pump run and felt the pulses in the pedal). I tried several more times, but couldn't get them to activate, and haven't been able to since (I found a slippery side street and tried again today). This is why I suspect the differential speed/ABS sensor...?
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Jag
Dodge Dakota
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1/02/2005
21:56:28
| RE: Rear end hopping problem - stumper...
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Message:
My thoughts exactly. The rear ABS circuit sensor runs to the differential cover. I didn't know you were able to hear the ABS pump working the relief valves. I would bet for sure this is your problem. It could be something as simple as metal shavings on the magnetic pickup.
I would unplug the sensor to see if the problem persists (it will bring on your brake/anti-lock light but it should disappear with reinstallation or ECU clearance). If the problem does persist then there is a fault in your ABS motor/valving. Let me know.
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01dakota_355
Dodge Dakota
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1/03/2005
09:13:40
| RE: Rear end hopping problem - stumper...
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Thanks Jag. I think I will give that a try once it warms up. It's about -3F here right now. :)
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Dr. D
Dodge Dakota
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1/04/2005
00:18:09
| RE: Rear end hopping problem - stumper...
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Message:
My 99' SC was doing the same thing and I thought that it was
the rear drums but it turned out to be a front rotor that was
warped.
When you put on brakes the weight shifts forward and the tail
end of your truck gets lighter.
This caused the tail end of my truck to bounce.
My steering wheel would never indicate front rotor problems
either.
CHECK YOUR FRONT ROTORS FIRST !!
Dr. D
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Doug
Dodge Dakota
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1/04/2005
10:42:09
|  RE: Rear end hopping problem - stumper...
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I have a 99 that would hop when applying the brakes at about 40 mph. I did everything too and finally replaced the front Rotors and that fixed the problem. I got them at Advance Auto Parts about 25,000 miles ago and they are still going strong.
Doug
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01dakota_355
Dodge Dakota
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1/05/2005
11:36:59
| RE: Rear end hopping problem - stumper...
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Yet another good idea to try. I don't think the fronts aren't warped too bad, but I can feel it in the pedal a bit, so they must be warped some amount. Thanks!
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01dakota_355
Dodge Dakota
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1/08/2005
16:49:58
| RE: Rear end hopping problem - stumper...
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Problem solved!!
Thanks, Dr. D and Doug; you two were right. I put new rotors on, and it stops like new. No hopping at all.
Good lesson learned, and no cash spent (9 mo. old rotors were still under 'customer satisfaction' warranty, so were replaced free).
It's too bad the brakes warp so often. I guess if I can keep getting the parts replaced under warranty, I don't mind the work every now and then...it's a good way to inspect everything periodically anyway :)
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