spring pad measurements - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BLAZIN'72 · 04-25-2003, 11:52 AM

I am installing 3/4 ton axles on my blazer they are out of a 77 gmc truck, I sold my old axles a while ago (and never took measurements) I know the front bolts right in but the rear spring pads and shock mounts have to be moved. I need the measurements between the pads and shock mounts, or if the truck has 3/4 ton axles the measurement from the drum to the front of pad and shock mount. Any help would be greatly appriciated. Thanks, Robert My truck is a 72 k5 blazer, thanks!

Beast388 · 04-25-2003, 01:48 PM

I am doing the same swap on my Suburban. I snagged my 3/4 ton axles from under a 77 K20 as well. The rear 14 bolt's stock spring perch distance is 42.5" center to center. You will need to cut off the old perches and weld new ones on at a spacing of 40" center to center. You will also need to cut off the shock tabs and move them as well. I was able to grind the welds on the old tabs to remove them in a way that I could reuse them. IIRC, the shock tab spacing is 25" C to C.

Here is a link to my Webshots album showing my 14 bolt build up. You will see my homemade perches as well as the shock tab location. Let me know if you have any other questions.

BLAZIN'72 · 04-25-2003, 02:51 PM

Thanks! Those perches look bulletproof! Did you buy the rear disc conv. complete or piece it together?

Beast388 · 04-25-2003, 07:03 PM

I made the perches out of 2.5 X2.5 X 0.25" wall thickness square tubing. I cut the pieces 5" long and notched them for the 3-3/8" diameter axle. I then boxed the ends in with 0.25" thick plate and ground the welds smooth. I don't think they will ever fail me.

As far as the disk drakes go, I am piecing it together. I bought the caliper brackets from Echobit for $70 shipped and the brake hose kit from A-tron for $62 shipped. The rotors and calipers I purchased from Autozone. They fit a 1977 K20 Dana 44.

Here are a few articles that describe the disk brake swap:
Article 1
Article 2
Article 3

BLAZERMAN · 04-27-2003, 12:36 AM

Beast, nice job on the spring perches, much stronger than the factory ones, I'd like to hear how you like the rear disc setup when you get it done.

Beast388 · 04-27-2003, 04:34 PM

Thanks Blazerman......
I decided to make my own perches instead of paying $50 for a set through a guy on ColoradoK5.com. I was able to get the steel free from work so they only cost me my time.

I am anxious to see how much improvemt there is with the rear discs. Hopefully it will stop my heavy Burb better than the factory set-up. I will keep ya posted!

04-25-2003, 11:52 AM	#1
BLAZIN'72 Active Member Join Date: Mar 2003 Location: Ontario,CA. Posts: 108	spring pad measurements I am installing 3/4 ton axles on my blazer they are out of a 77 gmc truck, I sold my old axles a while ago (and never took measurements) I know the front bolts right in but the rear spring pads and shock mounts have to be moved. I need the measurements between the pads and shock mounts, or if the truck has 3/4 ton axles the measurement from the drum to the front of pad and shock mount. Any help would be greatly appriciated. Thanks, Robert My truck is a 72 k5 blazer, thanks! Last edited by BLAZIN'72; 04-25-2003 at 12:01 PM.

04-25-2003, 01:48 PM	#2
Beast388 Suburbans RULE! Join Date: Jan 2000 Location: Clinton, IA 52732 Posts: 689	I am doing the same swap on my Suburban. I snagged my 3/4 ton axles from under a 77 K20 as well. The rear 14 bolt's stock spring perch distance is 42.5" center to center. You will need to cut off the old perches and weld new ones on at a spacing of 40" center to center. You will also need to cut off the shock tabs and move them as well. I was able to grind the welds on the old tabs to remove them in a way that I could reuse them. IIRC, the shock tab spacing is 25" C to C. Here is a link to my Webshots album showing my 14 bolt build up. You will see my homemade perches as well as the shock tab location. Let me know if you have any other questions. __________________ --Ben 71 GMC Suburban 4X4 The "Beast" 388 CID Stroker, TH350, NP205, 8-lug D44, 14BFF w/ Detroit, 4.10:1 gears, 4-Wheel Disks 4" Lift, 35" MT/R's.

04-25-2003, 07:03 PM	#4
Beast388 Suburbans RULE! Join Date: Jan 2000 Location: Clinton, IA 52732 Posts: 689	I made the perches out of 2.5 X2.5 X 0.25" wall thickness square tubing. I cut the pieces 5" long and notched them for the 3-3/8" diameter axle. I then boxed the ends in with 0.25" thick plate and ground the welds smooth. I don't think they will ever fail me. As far as the disk drakes go, I am piecing it together. I bought the caliper brackets from Echobit for $70 shipped and the brake hose kit from A-tron for $62 shipped. The rotors and calipers I purchased from Autozone. They fit a 1977 K20 Dana 44. Here are a few articles that describe the disk brake swap: Article 1 Article 2 Article 3 __________________ --Ben 71 GMC Suburban 4X4 The "Beast" 388 CID Stroker, TH350, NP205, 8-lug D44, 14BFF w/ Detroit, 4.10:1 gears, 4-Wheel Disks 4" Lift, 35" MT/R's.

04-27-2003, 12:36 AM	#5
BLAZERMAN Currently Blazerless Join Date: Apr 2000 Location: St. Joseph Mo. Posts: 4,828	Beast, nice job on the spring perches, much stronger than the factory ones, I'd like to hear how you like the rear disc setup when you get it done. __________________ 1972 C/30 133" W.B. C&C 1970 GMC 3500 157" W.B. single wheel C&C

04-27-2003, 04:34 PM	#6
Beast388 Suburbans RULE! Join Date: Jan 2000 Location: Clinton, IA 52732 Posts: 689	Thanks Blazerman...... I decided to make my own perches instead of paying $50 for a set through a guy on ColoradoK5.com. I was able to get the steel free from work so they only cost me my time. I am anxious to see how much improvemt there is with the rear discs. Hopefully it will stop my heavy Burb better than the factory set-up. I will keep ya posted! __________________ --Ben 71 GMC Suburban 4X4 The "Beast" 388 CID Stroker, TH350, NP205, 8-lug D44, 14BFF w/ Detroit, 4.10:1 gears, 4-Wheel Disks 4" Lift, 35" MT/R's.

04-25-2003, 02:51 PM	#3
BLAZIN'72 Active Member Join Date: Mar 2003 Location: Ontario,CA. Posts: 108	Thanks! Those perches look bulletproof! Did you buy the rear disc conv. complete or piece it together?



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