need rear end advice - The 1947 - Present Chevrolet & GMC Truck Message Board Network

easy_13 · 07-09-2004, 05:21 PM

I have a 72 Blazer CST 4x4. I broke something in my rear end (12 bolt, I think it's 3.08 but I haven't taken it apart to look). Should I:
1. Rebuild differential
2. Order new differential
3. Replace entire axles, etc.,
4. Upgrade to newer axles, etc.
What are approximate costs and reliability of each?
Thanks,
Mike

bouncytruck · 07-09-2004, 06:37 PM

Is your truck lifted? What size tires are you running?

1/2 ton running gear is easy to find. You might consider finding someone who is swapping out the 1/2 gear and just put that under your truck. If your truck is lifted and your running tires bigger than 35's (hopefully not with 3.08s), it is a good time to put some 3/4 or 1 ton running gear under your rig.

easy_13 · 07-10-2004, 01:01 PM

Bouncy,
I found the tag on the front diff and it has 3.73 gears.
Right now it has 6" lift and 35s; although I am considering going to 4" or even no lift and 33s. I'd like to make this a daily driver.

3wbdriver · 07-11-2004, 10:26 AM

When I bought Da Beast back in '89, it had 3.73's in it, with a 4" lift and 36" tires. It would only turn 1800 at 55mph, and you could tell the engine just wasn't comfortable there. Mine is happier with a 4.11 in it, on 35's now. But with the national speed limit back up, I don't do much passing on any interstates. Now it turns about 25-2600 at 55mph, and is pushing 3,000 to keep up on the interstate. Of course that's with an I don't know how old tach, and a wobbly speedo cable. I also run a standard tranny, and tow a race car (between 4000-4500lbs). And I haven't used 4wd in years because of 2 different ratios. If you're going to change the rear, ya gotta change the front to match. If you're running an auto, and plan on downsizing the tire size, I'd stick with the 3.73, and save the cost of re-gearing the front end. AND with the 3.73 I was getting 12.25 mgg. With the 4.11 I'm just now coaxing it back up to 11+. With gas prices what they are, you might take that into account too.

07-09-2004, 05:21 PM	#1
easy_13 Registered User Join Date: Apr 2003 Location: London, Ky. Posts: 38	need rear end advice I have a 72 Blazer CST 4x4. I broke something in my rear end (12 bolt, I think it's 3.08 but I haven't taken it apart to look). Should I: 1. Rebuild differential 2. Order new differential 3. Replace entire axles, etc., 4. Upgrade to newer axles, etc. What are approximate costs and reliability of each? Thanks, Mike

07-09-2004, 06:37 PM	#2
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Is your truck lifted? What size tires are you running? 1/2 ton running gear is easy to find. You might consider finding someone who is swapping out the 1/2 gear and just put that under your truck. If your truck is lifted and your running tires bigger than 35's (hopefully not with 3.08s), it is a good time to put some 3/4 or 1 ton running gear under your rig. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

07-11-2004, 10:26 AM	#4
3wbdriver Registered User Join Date: Aug 2003 Location: West Central Louisiana Posts: 82	When I bought Da Beast back in '89, it had 3.73's in it, with a 4" lift and 36" tires. It would only turn 1800 at 55mph, and you could tell the engine just wasn't comfortable there. Mine is happier with a 4.11 in it, on 35's now. But with the national speed limit back up, I don't do much passing on any interstates. Now it turns about 25-2600 at 55mph, and is pushing 3,000 to keep up on the interstate. Of course that's with an I don't know how old tach, and a wobbly speedo cable. I also run a standard tranny, and tow a race car (between 4000-4500lbs). And I haven't used 4wd in years because of 2 different ratios. If you're going to change the rear, ya gotta change the front to match. If you're running an auto, and plan on downsizing the tire size, I'd stick with the 3.73, and save the cost of re-gearing the front end. AND with the 3.73 I was getting 12.25 mgg. With the 4.11 I'm just now coaxing it back up to 11+. With gas prices what they are, you might take that into account too. __________________ '72 Blazer, 4WD, 350/4 spd. Affectionately known as "Da Beast" '04 Silverado (new daily driver) '00 Intrepid (wife's ride) It's a BLAZER dude! No options, no emblems, no a/c, no fancy shmancy. It's a BLAZER....

07-10-2004, 01:01 PM	#3
easy_13 Registered User Join Date: Apr 2003 Location: London, Ky. Posts: 38	Bouncy, I found the tag on the front diff and it has 3.73 gears. Right now it has 6" lift and 35s; although I am considering going to 4" or even no lift and 33s. I'd like to make this a daily driver.



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