Front Shackle Hole Diameter - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Baketown Scotty** · 11-06-2024, 08:13 PM

1966 GMC Suburban 4x4

Installing new shackle assembly on the rear front leaf springs. The holes in the shackles are not large enough to go past the threads onto the smooth section of the bolt. One side is slightly larger than the other allowing the one side to just start onto the smooth section. I can force them on a bit more but I'm sure I will destroy the threads. With the shackles on this far or even farther the shackles will not rotate from front to back, like they are practically pressed on. Should I open up these holes so they will rotate or are they supposed to be that tight?

**Baketown Scotty** · 11-08-2024, 02:41 PM

Maybe I am thinking about this all wrong. Should the shackles not swing freely and only swing front to back by the weight of the vehicle?

leegreen · 11-08-2024, 07:17 PM

Do you have the old shackles for comparison?

The shackles should swing back and forth. The diagram shows a greaseable bushing in each.

I'd expect the shackle to tighten down onto the shaft so the shaft turns in the bushing. You describe the shackles as almost fitting over the shaft, this does not sound right, I'd expect a more significant shoulder to tighten to. Are the holes stepped?

Maybe take the grease seals off, put it back together and see how it looks moves. If it is just the grease seal binding that is making it stiff it will soon free up. But the fit of shackles onto pin needs to be secure

**Baketown Scotty** · 11-09-2024, 04:47 PM

Lee green, you are correct. LMC sent lock nuts and instead of lock washers and nuts. Without the lock washers there is room to tighten the shackle down on to the smooth area of the pin. The shackles are in there tight but with the greased bushing rotating that will work just fine. Thank you for the help.

**kwmech** · 11-19-2024, 11:47 AM

Personally I wouldn't go off what LMC has to say. I've been getting nothing but crap from them lately and am moving on to other suppliers. Get rid of the hardware they gave you and go with a Gr 8 bolt. Later model front shackle bolts were 7/16 for quite a while and later upgraded to 1/2''. I dont know what you have there, but I've never seen lock washers on shackles, they've always been a self locking crimp nut on the factory stuff. Aftermarket usually uses the same style setup. Looking like that does, it appears the shackle plate has to sit on the shoulder of the bolt to leave room for the nut to get full thread contact. That is of course you are trying to go with all period correct looking OE stuff.

11-06-2024, 08:13 PM	#1
Baketown Scotty Junior Member Join Date: Oct 2005 Location: Bakersfield, CA Posts: 314	Front Shackle Hole Diameter 1966 GMC Suburban 4x4 Installing new shackle assembly on the rear front leaf springs. The holes in the shackles are not large enough to go past the threads onto the smooth section of the bolt. One side is slightly larger than the other allowing the one side to just start onto the smooth section. I can force them on a bit more but I'm sure I will destroy the threads. With the shackles on this far or even farther the shackles will not rotate from front to back, like they are practically pressed on. Should I open up these holes so they will rotate or are they supposed to be that tight? Attached Images __________________ 1964 Chevy Suburban 4x4 1966 GMC Suburban 4x4

11-08-2024, 02:41 PM	#2
Baketown Scotty Junior Member Join Date: Oct 2005 Location: Bakersfield, CA Posts: 314	Re: Front Shackle Hole Diameter Maybe I am thinking about this all wrong. Should the shackles not swing freely and only swing front to back by the weight of the vehicle? __________________ 1964 Chevy Suburban 4x4 1966 GMC Suburban 4x4

11-08-2024, 07:17 PM	#3
leegreen Registered User Join Date: Mar 2022 Location: Surrey BC Posts: 916	Re: Front Shackle Hole Diameter Do you have the old shackles for comparison? The shackles should swing back and forth. The diagram shows a greaseable bushing in each. I'd expect the shackle to tighten down onto the shaft so the shaft turns in the bushing. You describe the shackles as almost fitting over the shaft, this does not sound right, I'd expect a more significant shoulder to tighten to. Are the holes stepped? Maybe take the grease seals off, put it back together and see how it looks moves. If it is just the grease seal binding that is making it stiff it will soon free up. But the fit of shackles onto pin needs to be secure

11-09-2024, 04:47 PM	#4
Baketown Scotty Junior Member Join Date: Oct 2005 Location: Bakersfield, CA Posts: 314	Re: Front Shackle Hole Diameter Lee green, you are correct. LMC sent lock nuts and instead of lock washers and nuts. Without the lock washers there is room to tighten the shackle down on to the smooth area of the pin. The shackles are in there tight but with the greased bushing rotating that will work just fine. Thank you for the help. __________________ 1964 Chevy Suburban 4x4 1966 GMC Suburban 4x4

11-19-2024, 11:47 AM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,631	Re: Front Shackle Hole Diameter Personally I wouldn't go off what LMC has to say. I've been getting nothing but crap from them lately and am moving on to other suppliers. Get rid of the hardware they gave you and go with a Gr 8 bolt. Later model front shackle bolts were 7/16 for quite a while and later upgraded to 1/2''. I dont know what you have there, but I've never seen lock washers on shackles, they've always been a self locking crimp nut on the factory stuff. Aftermarket usually uses the same style setup. Looking like that does, it appears the shackle plate has to sit on the shoulder of the bolt to leave room for the nut to get full thread contact. That is of course you are trying to go with all period correct looking OE stuff.



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