1971 K10 U-bolt Issues (Rusty, Not So Trusty) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WyldeMoose · 05-25-2024, 07:42 PM

I have my '71 Chevy K10 completely apart. I decided it would be a good time to put a small 2.5" lift on it. When I got to the rear passenger side, the bracket that holds the U-bolts, or the rear anchor spring plate (whatever it's called) broke. I can't find anything online to help me find the right size.

I measured them and got 3.250" from peak to peak and 4" from center of one hole to the center of the other like the attached picture. I'm told that's the wrong size. My rear end is a 12 bolt rear end, and I'd think based on how terrible the rust is/was that it's all original.

I can't do anything else with the lift until I can replace that. Any help would be extremely appreciated!

Also, I searched the whole site and asked questions in a Facebook group and got more confused. I was told that the 12 bolt only has a 3", not the 3.250" I measured. However, the plate fit snug on the axle.

Any other questions or anything I missed, please just ask and I will answer to the best of my (limited) knowledge.

**1970cstblazer** · 05-26-2024, 07:27 AM

You are looking for orig. GM pt. # 3824491. Later changed to 3762845 and 3996593. Applications include 1969-72 Blazer, 1971-72 K10/K20 exc. HD rear springs.

Per 5/81 Parts book:

GR. 7.518 PLATE, REAR SPRING U BOLT ANCHOR
QTY 2 3762845

65-66 K10-Kg10
69-71 K10-K910-K15
71 K20-K25 W/STD
SPRINGS .... /SUP 3824491

WyldeMoose · 05-27-2024, 04:35 PM

Quote:

Originally Posted by 1970cstblazer

You are looking for orig. GM pt. # 3824491. Later changed to 3762845 and 3996593. Applications include 1969-72 Blazer, 1971-72 K10/K20 exc. HD rear springs.

Per 5/81 Parts book:

GR. 7.518 PLATE, REAR SPRING U BOLT ANCHOR
QTY 2 3762845

65-66 K10-Kg10
69-71 K10-K910-K15
71 K20-K25 W/STD
SPRINGS .... /SUP 3824491

Yes! That's exactly it. I took the broken one off and remeasured. It is definitely only 3" and not the 3.250" I thought. I looked up the parts numbers you offered and it says they are for 73-87 Square Body trucks with 3.5" axles. They look quite similar, but I'm just worried about the size they're made for. Either way, thank you for the response!

**jerry moss** · 05-28-2024, 10:48 PM

if you can't find them p.m. me, i've got a few of them laying around my parts stash.

**jerry moss** · 05-30-2024, 09:56 PM

Quote:

Originally Posted by WyldeMoose

Yes! That's exactly it. I took the broken one off and remeasured. It is definitely only 3" and not the 3.250" I thought. I looked up the parts numbers you offered and it says they are for 73-87 Square Body trucks with 3.5" axles. They look quite similar, but I'm just worried about the size they're made for. Either way, thank you for the response!

square body U bolts were mounted with the plate on top of the spring pack not under the axle like your picture

05-25-2024, 07:42 PM	#1
WyldeMoose Registered User Join Date: Aug 2020 Location: Jamestown, NY Posts: 2	1971 K10 U-bolt Issues (Rusty, Not So Trusty) I have my '71 Chevy K10 completely apart. I decided it would be a good time to put a small 2.5" lift on it. When I got to the rear passenger side, the bracket that holds the U-bolts, or the rear anchor spring plate (whatever it's called) broke. I can't find anything online to help me find the right size. I measured them and got 3.250" from peak to peak and 4" from center of one hole to the center of the other like the attached picture. I'm told that's the wrong size. My rear end is a 12 bolt rear end, and I'd think based on how terrible the rust is/was that it's all original. I can't do anything else with the lift until I can replace that. Any help would be extremely appreciated! Also, I searched the whole site and asked questions in a Facebook group and got more confused. I was told that the 12 bolt only has a 3", not the 3.250" I measured. However, the plate fit snug on the axle. Any other questions or anything I missed, please just ask and I will answer to the best of my (limited) knowledge. Attached Images

05-26-2024, 07:27 AM	#2
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,686	Re: 1971 K10 U-bolt Issues (Rusty, Not So Trusty) You are looking for orig. GM pt. # 3824491. Later changed to 3762845 and 3996593. Applications include 1969-72 Blazer, 1971-72 K10/K20 exc. HD rear springs. Per 5/81 Parts book: GR. 7.518 PLATE, REAR SPRING U BOLT ANCHOR QTY 2 3762845 65-66 K10-Kg10 69-71 K10-K910-K15 71 K20-K25 W/STD SPRINGS .... /SUP 3824491 __________________ 1970 K/5 Blazer CST 4WD, Medium Bronze, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion.. 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 45k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 62k miles, 3.6, 8L45, 3.23 LS, 18" wheels Last edited by 1970cstblazer; 05-26-2024 at 07:46 AM.

05-28-2024, 10:48 PM	#4
jerry moss Born Psycho Join Date: Feb 2001 Location: brentwood,cal,usa Posts: 4,915	Re: 1971 K10 U-bolt Issues (Rusty, Not So Trusty) if you can't find them p.m. me, i've got a few of them laying around my parts stash. __________________ jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA



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