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krue · 10-04-2005, 03:17 PM

I have a 72 Blazer that makes a ratcheting grinding sound from the front right side when it's in 4 low under a load. I was trying to pull a tree trunk out of the road when a limb at the top dug in. It started to make that racket and wasn't going anywhere. What did I break and how do I fix it?

CyberRanger · 10-04-2005, 03:40 PM

That sounds like your spider or side gears in the diff went south. I know this sound from experience. That is probably the weak point in the front axle.

**kwmech** · 10-04-2005, 03:43 PM

Could also be the CV joint in the front driveshaft.

CyberRanger · 10-04-2005, 03:55 PM

'72 Blazer doesn't have a CV joint. It has a u-joint & it generally doesn't make a grinding sound, but a nice "clunk".

74 shorty · 10-04-2005, 07:00 PM

Lockouts may have been stripped. Does it sound as though it is coming from hub. I f so its the splines in lockout. Factory ones are not that tough. lock in 4low and jack the tire that is on the side of the noise, may or may not be able to rotate tire but if you can you maybe able to pin point noise.

krue · 10-05-2005, 12:30 PM

Does sound like the hub to me. Where can I get replacements and how much are they gonna set me back?

a28doc · 10-05-2005, 01:16 PM

summit racing has them for your truck for 54 to 65 bucks good luck Doc

74 shorty · 10-05-2005, 06:36 PM

The last time I bought lockouts, They were manual warn premium lockouts and they cost me about 75 at the local parts store. Some people like Milemarkers and some prefer warn. I have never had problems with either. If your hubs are automatic I do suggests that you switch them to manual unless you don't do much offroading. About the same price as manuals but with manuals it frees up your whole front end. Either way you go make sure you have all the right tools and if you have never done it before;either an experienced friend or a shop manual. Not a good place for trial and error.

CyberRanger · 10-07-2005, 09:45 PM

'72 & earlier trucks never had automatic hubs. Automatic hubs were pretty whimpy & unreliable. '72 factory hubs were pretty good. Not many broke unless the truck had big tires & plenty of horses to boot.

The locking hub is easy enough to pull off & check. 6 hex head screws & it'll come right out. It'll be obvious if its bad. While its out, lock the other hub & put it in 4wd. You should not be able to turn the axle shaft on that side. If you can, then its your spider/side gears in the diff. I've seen a lot of folks take out the spiders & side gears while backing up pulling something... myself included.

10-04-2005, 03:17 PM	#1
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Need help I have a 72 Blazer that makes a ratcheting grinding sound from the front right side when it's in 4 low under a load. I was trying to pull a tree trunk out of the road when a limb at the top dug in. It started to make that racket and wasn't going anywhere. What did I break and how do I fix it? __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck" Last edited by krue; 10-04-2005 at 03:18 PM.

10-04-2005, 03:40 PM	#2
CyberRanger Registered User Join Date: Dec 2004 Location: North Central Colorado Posts: 38	That sounds like your spider or side gears in the diff went south. I know this sound from experience. That is probably the weak point in the front axle. __________________ '71 K20 Custom Deluxe - 1 owner - Original 350 & 4 spd, Rams horn dual exhaust, Centerforce clutch, K&N 4"x15", factory tow hooks, 4" Skyjacker Softride, Rancho RSX9000s, custom Firestone AirRide overloads, 36" 305/85R16 10ply Buckshot Mudders, 4.11 gears

10-04-2005, 03:55 PM	#4
CyberRanger Registered User Join Date: Dec 2004 Location: North Central Colorado Posts: 38	'72 Blazer doesn't have a CV joint. It has a u-joint & it generally doesn't make a grinding sound, but a nice "clunk". __________________ '71 K20 Custom Deluxe - 1 owner - Original 350 & 4 spd, Rams horn dual exhaust, Centerforce clutch, K&N 4"x15", factory tow hooks, 4" Skyjacker Softride, Rancho RSX9000s, custom Firestone AirRide overloads, 36" 305/85R16 10ply Buckshot Mudders, 4.11 gears

10-05-2005, 12:30 PM	#6
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Does sound like the hub to me. Where can I get replacements and how much are they gonna set me back? __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

10-05-2005, 01:16 PM	#7
a28doc '87 V20 4x4 Join Date: Jun 2004 Location: South Western Ohio Posts: 1,073	summit racing has them for your truck for 54 to 65 bucks good luck Doc __________________ '86 K5 Blazer 4x4 FOR SALE '87 v20 4X4 '99 S10 Blazer 4X4

10-04-2005, 03:43 PM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,659	Could also be the CV joint in the front driveshaft.

10-04-2005, 07:00 PM	#5
74 shorty Registered User Join Date: Aug 2005 Location: Bowling Green, Mo Posts: 98	Lockouts may have been stripped. Does it sound as though it is coming from hub. I f so its the splines in lockout. Factory ones are not that tough. lock in 4low and jack the tire that is on the side of the noise, may or may not be able to rotate tire but if you can you maybe able to pin point noise.

10-05-2005, 06:36 PM	#8
74 shorty Registered User Join Date: Aug 2005 Location: Bowling Green, Mo Posts: 98	The last time I bought lockouts, They were manual warn premium lockouts and they cost me about 75 at the local parts store. Some people like Milemarkers and some prefer warn. I have never had problems with either. If your hubs are automatic I do suggests that you switch them to manual unless you don't do much offroading. About the same price as manuals but with manuals it frees up your whole front end. Either way you go make sure you have all the right tools and if you have never done it before;either an experienced friend or a shop manual. Not a good place for trial and error.

10-07-2005, 09:45 PM	#9
CyberRanger Registered User Join Date: Dec 2004 Location: North Central Colorado Posts: 38	'72 & earlier trucks never had automatic hubs. Automatic hubs were pretty whimpy & unreliable. '72 factory hubs were pretty good. Not many broke unless the truck had big tires & plenty of horses to boot. The locking hub is easy enough to pull off & check. 6 hex head screws & it'll come right out. It'll be obvious if its bad. While its out, lock the other hub & put it in 4wd. You should not be able to turn the axle shaft on that side. If you can, then its your spider/side gears in the diff. I've seen a lot of folks take out the spiders & side gears while backing up pulling something... myself included. __________________ '71 K20 Custom Deluxe - 1 owner - Original 350 & 4 spd, Rams horn dual exhaust, Centerforce clutch, K&N 4"x15", factory tow hooks, 4" Skyjacker Softride, Rancho RSX9000s, custom Firestone AirRide overloads, 36" 305/85R16 10ply Buckshot Mudders, 4.11 gears



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