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76 Pacer - Rear End Vibration

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vangremlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vangremlin Quote  Post ReplyReply Direct Link To This Post Topic: 76 Pacer - Rear End Vibration
    Posted: Mar/12/2018 at 12:31pm
Hey, were you ever able to solve the vibration problem? I'm having similar issues with my Gremlin. Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2017 at 5:59am
The yoke is the same as for any other AMC, and likely Chrylser also... for 1972 and up with Chrysler transmissions. Any trans shop can get one, or try http://www.dennysdriveshaft.com/c73_dodge.html
Just tell the local shops it's a Chrysler trans. Would be a 904 for a six, 998 for the 304 V-8. All the bigger AMC V-8s used the 727, but you could have the smaller trans if someone has done an engine swap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2017 at 9:14pm
Do you know where I could buy a new yoke for my Pacer? i spent a little time looking but I couldn't find one. 
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/02/2017 at 7:38am
I had some driveline vibrations and couldn't figure them out. Took the driveshaft to a shop for balancing and making an inch longer, and they found the splines were damaged in the yoke and binding a bit. Said that was more likely my problem than length (had 2.50" inside trans, 2.25" out -- Jag IRS so not much in/out movement). Lengthened it anyway, but got a new yoke also. Problem solved! So check and see if the yoke slides in/out easily while you have the trans out. I was going to change the housing bushing again as I thought that was the source of a bit of bind. I'd changed it myself years ago, thought maybe I'd deformed it a bit when driving in. The new one slid in/out perfectly though. This was an AW4 trans, but that shouldn't matter.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 5:33pm
Yep, and those Torqueflites do like to leak!
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 4:22pm
Originally posted by CamJam CamJam wrote:

Originally posted by mantonas mantonas wrote:

No! I never did that! Thanks for reminding me. I think I have one, I just need to put it in. It's heck getting old and forgetting things all the time.

Well if not, they're only $8.99 at O'Reillys (assuming you have the 232 motor) same as what I paid for the Javelin with a 998 transmission. Different part number, but the design of yours is the same as mine-- just probably a different height.  You can see how the right angle metal "blade" is (barely) attached to the rubber.  In my case, half the rubber was gone entirely. 
 

Just FYI, the mount as pictured in the O'Reilly's photo is upside down.


What he said.  X2.  If that mount is toast, and from what you've written earlier it is, you can do all the balancing and parts changing you want...and you'll still have vibration.  Thing to remember is that an AMC 6 cylinder engine with an automatic transmission is roughly 1/2 the length of the entire car - which also means that the torque of the engine has a very long 'beam' to exert it's force on - and the only thing that is keeping it in check is the rear mount.  Can't tell you how many of those I've broken over the years, and many times not from abuse - a big ol block of rubber that has oil spraying on it all the time is only gonna last but just so long.
73 Gremlin 401/5-spd.
77 Matador Wagon 360/727.
81 Jeep J10 LWB 360/4-spd
83 Concord DL 4-dr 258/auto

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Post Options Post Options   Thanks (1) Thanks(1)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 10:38am
Originally posted by mantonas mantonas wrote:

No! I never did that! Thanks for reminding me. I think I have one, I just need to put it in. It's heck getting old and forgetting things all the time.

Well if not, they're only $8.99 at O'Reillys (assuming you have the 232 motor) same as what I paid for the Javelin with a 998 transmission. Different part number, but the design of yours is the same as mine-- just probably a different height.  You can see how the right angle metal "blade" is (barely) attached to the rubber.  In my case, half the rubber was gone entirely. 
 

Just FYI, the mount as pictured in the O'Reilly's photo is upside down.
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 9:56am
No! I never did that! Thanks for reminding me. I think I have one, I just need to put it in. It's heck getting old and forgetting things all the time.
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 9:32am
Did you ever install that new transmission mount you bought? I just spent two months chasing a similar problem. Turned out to be the tranny mount. $8.99 at O'Reilly's and took all of 15 minutes to install.

The clue was the pinion angle. Transmission angle measured at the yoke and rear diff angle measured at flat spot on bottom of case should be within a couple degrees of each other. Mine differed by about 6 degrees because missing rubber of the mount was causing the rear of tranny to droop by about two inches. Tranny mount can appear good until you look closely and realize that the metal "blade" part of the mount is no longer bonded to the rubber.

Edited by CamJam - Sep/01/2017 at 9:43am
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Sep/01/2017 at 8:30am
I was hoping that the driveshaft would solve the problems, but it didn't. I now have a driveshaft that's worth at least 10 percent of the total value of the car. Talk about spending your children's inheritance. Anyway, the vibration is still there but now it's different. It starts at about 45 mph and sort of ends around 55 mph. Previously it would just continue to get worse the faster I went. I have now had it up to around 80 mph and while it is loud and feels like the world is coming to an end at that speed it's not because of the vibration. So I'm back to the bushing.

I called a transmission shop and they told me it would cost between $250 and $300 for them to replace it. If you want to do it with the transmission still in the car, then you need the mother of all special tools. Knowing that this car essentially has a Chrysler 904 Torqueflite in it I looked for the tool and this appears to be it:

https://www.atsg.us/atsg/extension-housing-bushing-remover-installer-and-output-shaft-support-fixture-party-t-0160-a.html

Still expensive ($179, presumably plus shipping and maybe tax) and I don't know if I would trust myself to use it properly.

Then yesterday I had a bit of good luck. A friend of mine from work gave me the name of a transmission repair guy that he has used who he says is good. This friend of mine has 5 kids and is the sole earner for his family, so when he says somebody is good, there's an unspoken "and cheap" that follows. And he was right: this transmission repair guy said he would remove the extension housing, knock out the bushing and replace it, and, while he was there, replace the tailshaft bearing, for a grand total of $100! 

So that's going to be my next step. I need to get into his shop sometime after Labor Day and I will see what it's like after that. If it still vibrates, I will probably start thinking about replacing rear wheel bearings. I've done a somewhat half-assed search for parts in preparation for that and I haven't found any, so that could be a problem.

Another data point: I read on some forum that maybe a vibration like this could be from the engine. It could be as simple as an engine cooling fan that's out of balance. The post said to throw it in neutral while the vibration is happening and see if it stops. So I did that, and it did stop, for a few seconds, then it started to come back. I interpret that to mean that when the transmission stops applying torque to the slip yoke, it disrupts the vibration, sort of like stomping on the brakes in a solid front axle Jeep to stop death wobble (some of you know what I mean!). You stop the vibrations temporarily by disturbing the system, but it eventually comes back. So I don't think it's coming from the engine.
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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