1971 GTX vibration issue "UPDATED PROBLEM SOLVED"
#1358272
12/24/12 01:24 AM
12/24/12 01:24 AM
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Joined: Jun 2005
Posts: 287 MI
AfterHoursResto
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I just finished a rotisserie restoration on a 1971 GTX 440 auto 8 ¾ with a 323 posi. I am experiencing a on and off type vibration with begins at 40mph - 65mph. It may continue past 65 but that is as fast as I have driven the car since completed.
I have placed the trans in N while rolling down the road and the vibration continues even though the engine drops down to an idle.
I am running tapered bearings in the rear axels set at .010 .012. The bushing was replaced in the tail shaft of the trans during its overhaul. The drive shaft is brand new and I also tried to but the old shaft in and it did not make a difference.
The center section is a 489 case and was rebuilt using the original ring and pinion.
Everything is brand new or rebuilt on this car. It was restored to factory specs with no performance modifications. I am stumped.
Any input would be appreciated.
Thanks
Last edited by AfterHoursResto; 02/10/13 10:22 PM.
Roman Sobilo
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Re: 1971 GTX vibration issue
[Re: AfterHoursResto]
#1358275
12/24/12 02:02 AM
12/24/12 02:02 AM
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Joined: Jan 2003
Posts: 18,632 jersey shore
flypaper
I hate Texas
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I hate Texas
Joined: Jan 2003
Posts: 18,632
jersey shore
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on a 71b body there is a weight that bolts to the floor above the driveshaft. it is there to help driveshaft vibration. is that weight missing? i can get you a pic of it, if you need to see what it looks like.
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Re: 1971 GTX vibration issue
[Re: RSNOMO]
#1358277
12/24/12 02:50 AM
12/24/12 02:50 AM
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Joined: Jun 2005
Posts: 287 MI
AfterHoursResto
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I have tried two sets of tires. A brand new set of G 60's and the old set of radios the car came with and there was no change.
The driveline angle is at 2.5.
Thereis no wieght on the tailshaft or floor board. Would like to see a pictures of one!
Roman Sobilo
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Re: 1971 GTX vibration issue
[Re: AfterHoursResto]
#1358278
12/24/12 03:58 AM
12/24/12 03:58 AM
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Joined: Jul 2004
Posts: 4,732 Watertown, WI
MikeyT
master
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master
Joined: Jul 2004
Posts: 4,732
Watertown, WI
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Could it be a bad u joint? I had the very thing happen last spring and it was a bad u joint. Also I thought pinion angle was suppose to range between 2.5-5.5 nose of diff down.
Mike
1969 Dodge Dart Swinger
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Re: 1971 GTX vibration issue
[Re: flypaper]
#1358279
12/24/12 09:50 AM
12/24/12 09:50 AM
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Joined: Nov 2008
Posts: 1,491 Lethbridge, AB, Canada
dangina
pro stock
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pro stock
Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
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Quote:
on a 71b body there is a weight that bolts to the floor above the driveshaft. it is there to help driveshaft vibration. is that weight missing?
i can get you a pic of it, if you need to see what it looks like.
could you take a pic? I'm in the middle of putting my 71 runner back together and I haven't seen or heard of this weight?
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Re: 1971 GTX vibration issue
[Re: BigMoneyLewis]
#1358281
12/24/12 11:34 AM
12/24/12 11:34 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I know you changed shafts but that'd be my guess, shaft or ujoints. How much freeplay does the shaft have into the trans? Want ~3/4" with the common aftermarket flat extension housing seal. I had too much & had a similar vibration that came & went. The correct slightly longer shaft took care of it. Holler how it goes
live every 24 hour block of time like it's your last day on earth
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Re: 1971 GTX vibration issue
[Re: dangina]
#1358282
12/24/12 11:36 AM
12/24/12 11:36 AM
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Joined: Nov 2003
Posts: 12,494 Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
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Posts: 12,494
Western Colorado High Desert
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Quote:
Quote:
on a 71b body there is a weight that bolts to the floor above the driveshaft. it is there to help driveshaft vibration. is that weight missing?
i can get you a pic of it, if you need to see what it looks like.
could you take a pic? I'm in the middle of putting my 71 runner back together and I haven't seen or heard of this weight?
The weight was not used on 71/2 HP cars. Just LP cars. It mounts in the top of the tunnel right at the seam between the rear footwell and the under rear seat pans. Has a plate with 3 studs welded to the floor and the weight mounts to the suds under the pans. I guess I don't have pics but can get some.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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Re: 1971 GTX vibration issue
[Re: moparmarks]
#1358283
12/24/12 11:53 AM
12/24/12 11:53 AM
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Joined: Jun 2005
Posts: 287 MI
AfterHoursResto
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Good suggestions everyone! Thanks.
Yes, the tires are mounted on two sets of rims. One set is about a year old and the other are brand new. So I don’t think it is the rims or tires.
Both shafts I tried have new u joints.
However, I do have more than ¾ sticking out of the tail shaft. Maybe someone swapped drive shafts out before I got my hands on the car.
Does anyone have the correct dimensions for a stock factory driveshaft (71 GTX 440 auto 8 ¾)?
Thanks
Roman Sobilo
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Re: 1971 GTX vibration issue
[Re: fourgearsavoy]
#1358286
12/24/12 01:20 PM
12/24/12 01:20 PM
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Joined: Jun 2005
Posts: 287 MI
AfterHoursResto
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I am getting ready to lift the rear, take the tires off, then the drums and see what happens. I will let you guys know. Thanks
Roman Sobilo
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Re: 1971 GTX vibration issue
[Re: RapidRobert]
#1358290
12/26/12 06:28 PM
12/26/12 06:28 PM
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Joined: Nov 2003
Posts: 12,494 Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
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Posts: 12,494
Western Colorado High Desert
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71 GTX 440/727/8.75 drive shaft is 50.75" center between joints.
Here is the non-HP weight and mounting bracket. I've had/have upwards of 20 71/2B HP cars and none had this weight. I did just partout a 73 Charger 400HP car that has this weight as well as all my 71/3 non-HP cars.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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