Rear Heavy Duty Coil Spring Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

harrydunn · 10-01-2014, 12:41 AM

'72 3/4-ton with Heavy Duty rear coils per the SPID (and visual inspection). I found a set of 1/2-ton rear coils from a '72 for next to nothing. I know the ride will be nicer but will it drop the rear at all? I'm not too concerned about the ride quality (it is FIRM but not terrible) but would like to drop the rear. May consider drop springs or blocks but would like to use the 1/2-ton springs if they will drop it at all since I've already got them. It has a serious rake to it and I'd like to level it out a bit!

Thanks.

harrydunn · 10-01-2014, 06:46 PM

ttt

**leddzepp** · 10-01-2014, 07:19 PM

IMO they won't, since they are the same height and not drop springs. But since you already have them why not give it a try and see what happens?

Coley · 10-01-2014, 07:24 PM

To my recollection, the 3/4ton frames have a slightly larger section modulus..which makes the frame slightly 'taller' than the 1/2 ton frame.
These means, all things being equal, the truck will generally sit a little higher as a result of this.
Now, I'm not sure how the lengths of the coils differ...if they differ. From a glance you would think the 3/4 ton coil would be slightly higher (and heavier duty) to carry more load and to reach up a bit more.
....just thinking out loud here.
Either way, I'd try it out....I think it would work and I think the rear height would settle down a bit and give a little better ride.
my two bits.
Coley

mechanicalman · 10-01-2014, 07:26 PM

Quote:

Originally Posted by leddzepp

IMO they won't, since they are the same height and not drop springs. But since you already have them why not give it a try and see what happens?

X2, too easy not to try.

**LockDoc** · 10-01-2014, 08:39 PM

-
I took the heavy duty coils out of my Suburban and put 1/2 ton progressive coils in it. It was originally an ambulance. Made all the difference in the world in the ride. Smooooth.... and it dropped it down a little.

LockDoc

harrydunn · 10-01-2014, 11:12 PM

Man, oh man. PB Blaster and my impact wrench are not budging the lower spring bolt. Put my cheater bar on it and I know I'm going to snap it so I'm laying off it for now. May take it to my mechanic friend and let him snap it off for me since he can fix it easier. :-) Tried the U-bolts for giggles with a cheater and 18" pipe and could not budge them.

Something I was surprised about: Rear springs are both only bolted onto the trailing arms. They are not bolted on top to the frame. Normal for a 3/4-ton with HD springs? Truck has been in my family since new and I can't imagine the rear springs ever being tinkered with. My grandfather and I are the only two owners.

harrydunn · 10-03-2014, 05:10 PM

Thoughts on the rear springs not being physically connected to the frame at the top?

Thanks.

**FirstOwner69** · 10-03-2014, 05:17 PM

They should be attached using cups like the bottom. My cups were mostly rusted away though.

Vintage Windmills · 10-05-2014, 02:36 PM

Yes, you are missing the cups to bolt it to the frame on top. You should see holes for a bolt there to mount the cups. I will try for a pic

Unless your truck is super rust free, a torch is really the only way to get any bolt that goes through the trailing arm out. Heat the arm along length of bolt.

mechanicalman · 10-05-2014, 03:30 PM

Quote:

Originally Posted by harrydunn

Man, oh man. PB Blaster and my impact wrench are not budging the lower spring bolt. Put my cheater bar on it and I know I'm going to snap it so I'm laying off it for now. May take it to my mechanic friend and let him snap it off for me since he can fix it easier. :-) Tried the U-bolts for giggles with a cheater and 18" pipe and could not budge them.

Something I was surprised about: Rear springs are both only bolted onto the trailing arms. They are not bolted on top to the frame. Normal for a 3/4-ton with HD springs? Truck has been in my family since new and I can't imagine the rear springs ever being tinkered with. My grandfather and I are the only two owners.

I had always assumed that HD 3/4 ton springs would not have progressive coils. Since I've joined this forum, however, I've learned a lot and found assumptions are just that, assumptions.

Anyone care to chime in on that?

**FirstOwner69** · 10-05-2014, 03:38 PM

Here's a picture of my 69 3/4 ton with original coils. Looks progressive to me.

mechanicalman · 10-05-2014, 03:45 PM

Quote:

Originally Posted by FirstOwner69

Here's a picture of my 69 3/4 ton with original coils. Looks progressive to me.

Yup, thanks for the info. Learning op!

**FirstOwner69** · 10-05-2014, 03:47 PM

Another picture below that I found that shows the edge of the retainer cup and the bolt through the frame. Also, here's a link to the cups I bought from CPP. However, the bolts supplied are too short. http://www.ebay.com/itm/1963-1972-CH...df9ec2&vxp=mtr

10-01-2014, 12:41 AM	#1
harrydunn Registered User Join Date: Dec 2010 Location: Columbia, MO Posts: 256	Rear Heavy Duty Coil Spring Question '72 3/4-ton with Heavy Duty rear coils per the SPID (and visual inspection). I found a set of 1/2-ton rear coils from a '72 for next to nothing. I know the ride will be nicer but will it drop the rear at all? I'm not too concerned about the ride quality (it is FIRM but not terrible) but would like to drop the rear. May consider drop springs or blocks but would like to use the 1/2-ton springs if they will drop it at all since I've already got them. It has a serious rake to it and I'd like to level it out a bit! Thanks. __________________ 1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport Last edited by harrydunn; 10-01-2014 at 12:52 AM.

10-01-2014, 06:46 PM	#2
harrydunn Registered User Join Date: Dec 2010 Location: Columbia, MO Posts: 256	Re: Rear Heavy Duty Coil Spring Question ttt __________________ 1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport

10-01-2014, 07:19 PM	#3
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 19,978	Re: Rear Heavy Duty Coil Spring Question IMO they won't, since they are the same height and not drop springs. But since you already have them why not give it a try and see what happens? __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man

10-01-2014, 07:24 PM	#4
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Re: Rear Heavy Duty Coil Spring Question To my recollection, the 3/4ton frames have a slightly larger section modulus..which makes the frame slightly 'taller' than the 1/2 ton frame. These means, all things being equal, the truck will generally sit a little higher as a result of this. Now, I'm not sure how the lengths of the coils differ...if they differ. From a glance you would think the 3/4 ton coil would be slightly higher (and heavier duty) to carry more load and to reach up a bit more. ....just thinking out loud here. Either way, I'd try it out....I think it would work and I think the rear height would settle down a bit and give a little better ride. my two bits. Coley __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500

10-01-2014, 08:39 PM	#6
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,315	Re: Rear Heavy Duty Coil Spring Question - I took the heavy duty coils out of my Suburban and put 1/2 ton progressive coils in it. It was originally an ambulance. Made all the difference in the world in the ride. Smooooth.... and it dropped it down a little. LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

10-01-2014, 11:12 PM	#7
harrydunn Registered User Join Date: Dec 2010 Location: Columbia, MO Posts: 256	Re: Rear Heavy Duty Coil Spring Question Man, oh man. PB Blaster and my impact wrench are not budging the lower spring bolt. Put my cheater bar on it and I know I'm going to snap it so I'm laying off it for now. May take it to my mechanic friend and let him snap it off for me since he can fix it easier. :-) Tried the U-bolts for giggles with a cheater and 18" pipe and could not budge them. Something I was surprised about: Rear springs are both only bolted onto the trailing arms. They are not bolted on top to the frame. Normal for a 3/4-ton with HD springs? Truck has been in my family since new and I can't imagine the rear springs ever being tinkered with. My grandfather and I are the only two owners. __________________ 1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport

10-03-2014, 05:10 PM	#8
harrydunn Registered User Join Date: Dec 2010 Location: Columbia, MO Posts: 256	Re: Rear Heavy Duty Coil Spring Question Thoughts on the rear springs not being physically connected to the frame at the top? Thanks. __________________ 1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport

10-03-2014, 05:17 PM	#9
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,838	Re: Rear Heavy Duty Coil Spring Question They should be attached using cups like the bottom. My cups were mostly rusted away though.

10-05-2014, 02:36 PM	#10
Vintage Windmills Vintage 4x4s Join Date: Sep 2010 Location: Prior Lake, MN Posts: 4,305	Re: Rear Heavy Duty Coil Spring Question Yes, you are missing the cups to bolt it to the frame on top. You should see holes for a bolt there to mount the cups. I will try for a pic Unless your truck is super rust free, a torch is really the only way to get any bolt that goes through the trailing arm out. Heat the arm along length of bolt. __________________ 67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ) 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6

10-05-2014, 03:38 PM	#12
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,838	Re: Rear Heavy Duty Coil Spring Question Here's a picture of my 69 3/4 ton with original coils. Looks progressive to me. Attached Images

10-05-2014, 03:47 PM	#14
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,838	Re: Rear Heavy Duty Coil Spring Question Another picture below that I found that shows the edge of the retainer cup and the bolt through the frame. Also, here's a link to the cups I bought from CPP. However, the bolts supplied are too short. http://www.ebay.com/itm/1963-1972-CH...df9ec2&vxp=mtr Attached Images Last edited by FirstOwner69; 10-05-2014 at 03:53 PM.

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