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Mopar SS spring question
#3223731
03/30/24 03:08 PM
03/30/24 03:08 PM
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Joined: Feb 2003
Posts: 7,982
Scranton, PA
Montclaire
OP
master
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OP
master
Joined: Feb 2003
Posts: 7,982
Scranton, PA
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Hello, I have a 74 Barracuda with an 8-3/4 and Mopar SS springs. The car has what looks like the Mopar front hangers with two bolt locations, and the springs are in the lower hole. I am getting a driveline vibration above 3,000 rpm/50-55 mph (the car has 3.91s). Checked the pinion angle and found it to be one degree positive.
I ordered a pair of four degree wedges to correct the pinion angle. The wedges are 3/8” thick at the midpoint, and I am assuming engagement of the center pin is going to be an issue. Does anyone know the length of the Mopar center pins? I’d like to pick up a new set in advance so I don’t make this into a two day project.
I have already done a precursory search and can’t find a length listed anywhere. I believe they are 5/16”. I’ve seen guys suggest using allen head bolts, although I have a few spring shops local to me so I probably won’t need to go that route. Would grade 8 allen bolts be sufficient if I do?
Thanks in advance.
Last edited by Montclaire; 03/30/24 03:13 PM.
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Re: Mopar SS spring question
[Re: Montclaire]
#3223763
03/30/24 05:29 PM
03/30/24 05:29 PM
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Joined: Mar 2011
Posts: 3,076
Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,076
Michigan
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Hello, I have a 74 Barracuda with an 8-3/4 and Mopar SS springs. The car has what looks like the Mopar front hangers with two bolt locations, and the springs are in the lower hole. I am getting a driveline vibration above 3,000 rpm/50-55 mph (the car has 3.91s). Checked the pinion angle and found it to be one degree positive.
I ordered a pair of four degree wedges to correct the pinion angle. The wedges are 3/8” thick at the midpoint, and I am assuming engagement of the center pin is going to be an issue. Does anyone know the length of the Mopar center pins? I’d like to pick up a new set in advance so I don’t make this into a two day project.
I have already done a precursory search and can’t find a length listed anywhere. I believe they are 5/16”. I’ve seen guys suggest using allen head bolts, although I have a few spring shops local to me so I probably won’t need to go that route. Would grade 8 allen bolts be sufficient if I do?
Thanks in advance. Once your u-bolts are tight the pin does nothing more than position the axle. Grade 8 bolts are more than adequate. Find something where the head is as close to the perch hole diameter as possible and either push the axle forward or back against the pin before tightening the u bolts.
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Re: Mopar SS spring question
[Re: A727Tflite]
#3223841
03/30/24 09:55 PM
03/30/24 09:55 PM
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Joined: Jan 2003
Posts: 15,355
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,355
Omaha Ne
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[
Once your u-bolts are tight the pin does nothing more than position the axle.
Grade 8 bolts are more than adequate. Find something where the head is as close to the perch hole diameter as possible and either push the axle forward or back against the pin before tightening the u bolts. I'm going to politely disagree with the bolded part  If one has enough motor and traction that pin is going to do more than locate the axle IMO. I'd suggest longer pins with heads of the correct diameter. If the pin portion is too short have spacers made to raise the pins a bit. One can measure the clamped spring thickness, add what's needed for the nut and lock washer (more is better  ) and visit your local spring shop. if they don't have longer pins, space them up. Just an FYI: placing two good sized c-clamps on opposing sides of the pin makes changing the pin quite easy  
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Re: Mopar SS spring question
[Re: TJP]
#3223864
03/30/24 10:53 PM
03/30/24 10:53 PM
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Joined: Mar 2011
Posts: 3,076
Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,076
Michigan
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[
Once your u-bolts are tight the pin does nothing more than position the axle.
Grade 8 bolts are more than adequate. Find something where the head is as close to the perch hole diameter as possible and either push the axle forward or back against the pin before tightening the u bolts. I'm going to politely disagree with the bolded part If one has enough motor and traction that pin is going to do more than locate the axle IMO. I'd suggest longer pins with heads of the correct diameter. If the pin portion is too short have spacers made to raise the pins a bit. One can measure the clamped spring thickness, add what's needed for the nut and lock washer (more is better ) and visit your local spring shop. if they don't have longer pins, space them up. Just an FYI: placing two good sized c-clamps on opposing sides of the pin makes changing the pin quite easy My statement wasn’t an opinion. I have seen quite a few rear suspensions in heavy, fast SS cars back in the day with oversized holes in the shock plates. Never been an issue. The u-bolt takes all the separation load. The alignment pin is in shear, which is minimal as long as the u-bolts remain tight. You will never break the pin.
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Re: Mopar SS spring question
[Re: A727Tflite]
#3224138
03/31/24 10:56 PM
03/31/24 10:56 PM
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Joined: Jan 2003
Posts: 15,355
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,355
Omaha Ne
|
[
Once your u-bolts are tight the pin does nothing more than position the axle.
Grade 8 bolts are more than adequate. Find something where the head is as close to the perch hole diameter as possible and either push the axle forward or back against the pin before tightening the u bolts. I'm going to politely disagree with the bolded part If one has enough motor and traction that pin is going to do more than locate the axle IMO. I'd suggest longer pins with heads of the correct diameter. If the pin portion is too short have spacers made to raise the pins a bit. One can measure the clamped spring thickness, add what's needed for the nut and lock washer (more is better ) and visit your local spring shop. if they don't have longer pins, space them up. Just an FYI: placing two good sized c-clamps on opposing sides of the pin makes changing the pin quite easy My statement wasn’t an opinion. I have seen quite a few rear suspensions in heavy, fast SS cars back in the day with oversized holes in the shock plates. Never been an issue. The u-bolt takes all the separation load. The alignment pin is in shear, which is minimal as long as the u-bolts remain tight. You will never break the pin. I didn't say it was an opinion, just that I disagreed with it and still do. I've seen many things done that people thought were OK and later found out different. That is a STATEMENT!! My previous comment was MY OPINION
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