gearing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

62 short step · 07-27-2006, 05:40 PM

Took the covers off the diffs today. Found 3.91 in front, 3.07 in back. Not good! The front gears look good, the back looks ok. I like the 3.07's in the back with my 4 speed, it cruises at 50 to 55 mph @ 2000 rpms. What I'm asking is what will the 3.91's do out back? Like I said before the 3.91's are in better shape. I know the obvious would be to put 3.91's out back. What do yall think?

62 short step · 07-27-2006, 05:45 PM

By the way the front is D44 5f and rear 12 bolt stock.

b454rat · 07-27-2006, 07:04 PM

Well the 3.91 will get you out of the hole faster, and of course turn more rpms driving down the road. You will have more power, pulling hills and such, also good for towing. Im building my burban with 3.08s in it so I can cruise down the road, not screaming rpms either.

62 short step · 07-27-2006, 08:06 PM

I called Randys ring & pinion and said could not get 3.91's for the 12 bolt? Didnt think about asking him about 3.07's for front dana 44. For what I use the truck for 3.07's should be fine. Any body got a set?

Americanrider · 08-14-2006, 12:41 PM

3.08/3.07's where standard in almost all Blazers, search your local 4x4 clubs B-boards and I'm sure your going to find someone with a axle or 2 for sale. Around here they go pretty cheap on craigslist.

**kwmech** · 08-14-2006, 10:31 PM

My first question would be is what size tire are you running?

There is also 22 percent difference in the ratios

62 short step · 08-15-2006, 07:09 AM

Quote:

Originally Posted by Americanrider

3.08/3.07's where standard in almost all Blazers, search your local 4x4 clubs B-boards and I'm sure your going to find someone with a axle or 2 for sale. Around here they go pretty cheap on craigslist.

I've been looking can not find any close to me yet. Salvage yards around here crush things to soon.

b454rat · 08-15-2006, 07:53 AM

I will/might be looking for a set of axles with 3.08s, I'll see if I can find a 12b with 3.08s, and pull the gears for yah.

62 short step · 08-15-2006, 07:07 AM

I'm running 265/ 75/16 and might go to 305's. Jeremy

2wdBlazer · 08-15-2006, 09:43 AM

If you go to a 305-75-16, that will be a 34 inch tire. Richt now you have a 31.6 inch tire. I would definatly not go with 3.07 and a 34 inch tire. Big mistake. If you keep the same size tires you will be ok.

62 short step · 08-15-2006, 04:15 PM

Quote:

Originally Posted by 2wdBlazer

If you go to a 305-75-16, that will be a 34 inch tire. Richt now you have a 31.6 inch tire. I would definatly not go with 3.07 and a 34 inch tire. Big mistake. If you keep the same size tires you will be ok.

What gears do you think I should use with the 305's? Jeremy

2wdBlazer · 08-15-2006, 10:09 PM

3.91 would be fine. That way you only have to mess with the one axle.

How does 2500 rpm sound at 65mph.

http://www.intercotire.com/site63.php

62 short step · 08-15-2006, 11:05 PM

Randys ring & pinion said that 3.91s were not available for the 12 bolt rear.

2wdBlazer · 08-15-2006, 11:52 PM

Check for a 3.90 ratio. Probably a hard one to get. 4.11 would be ideal for your application anyway.

62 short step · 08-16-2006, 07:04 AM

Thanks for the help. I'll let yall know what I come up with. Thanks again, Jeremy

07-27-2006, 05:40 PM	#1
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	gearing Took the covers off the diffs today. Found 3.91 in front, 3.07 in back. Not good! The front gears look good, the back looks ok. I like the 3.07's in the back with my 4 speed, it cruises at 50 to 55 mph @ 2000 rpms. What I'm asking is what will the 3.91's do out back? Like I said before the 3.91's are in better shape. I know the obvious would be to put 3.91's out back. What do yall think? __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

07-27-2006, 05:45 PM	#2
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: gearing By the way the front is D44 5f and rear 12 bolt stock. __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

07-27-2006, 07:04 PM	#3
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,469	Re: gearing Well the 3.91 will get you out of the hole faster, and of course turn more rpms driving down the road. You will have more power, pulling hills and such, also good for towing. Im building my burban with 3.08s in it so I can cruise down the road, not screaming rpms either. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 4” SAS 1999 GMC Yukon 350/4L60 6" SAS

07-27-2006, 08:06 PM	#4
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: gearing I called Randys ring & pinion and said could not get 3.91's for the 12 bolt? Didnt think about asking him about 3.07's for front dana 44. For what I use the truck for 3.07's should be fine. Any body got a set? __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

08-14-2006, 12:41 PM	#5
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	Re: gearing 3.08/3.07's where standard in almost all Blazers, search your local 4x4 clubs B-boards and I'm sure your going to find someone with a axle or 2 for sale. Around here they go pretty cheap on craigslist.

08-14-2006, 10:31 PM	#6
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,650	Re: gearing My first question would be is what size tire are you running? There is also 22 percent difference in the ratios Last edited by kwmech; 08-14-2006 at 10:34 PM.

08-15-2006, 07:53 AM	#8
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,469	Re: gearing I will/might be looking for a set of axles with 3.08s, I'll see if I can find a 12b with 3.08s, and pull the gears for yah. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 4” SAS 1999 GMC Yukon 350/4L60 6" SAS

08-15-2006, 07:07 AM	#9
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: gearing I'm running 265/ 75/16 and might go to 305's. Jeremy __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

08-15-2006, 09:43 AM	#10
2wdBlazer The Blazer King Join Date: Sep 2000 Location: Valrico, Fl (Tampa) Posts: 1,212	Re: gearing If you go to a 305-75-16, that will be a 34 inch tire. Richt now you have a 31.6 inch tire. I would definatly not go with 3.07 and a 34 inch tire. Big mistake. If you keep the same size tires you will be ok. __________________ 72 2wd Blazer. Its the superbichinest, megacoolinest, superflowinest.

08-15-2006, 10:09 PM	#12
2wdBlazer The Blazer King Join Date: Sep 2000 Location: Valrico, Fl (Tampa) Posts: 1,212	Re: gearing 3.91 would be fine. That way you only have to mess with the one axle. How does 2500 rpm sound at 65mph. http://www.intercotire.com/site63.php __________________ 72 2wd Blazer. Its the superbichinest, megacoolinest, superflowinest.

08-15-2006, 11:05 PM	#13
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: gearing Randys ring & pinion said that 3.91s were not available for the 12 bolt rear. __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

08-15-2006, 11:52 PM	#14
2wdBlazer The Blazer King Join Date: Sep 2000 Location: Valrico, Fl (Tampa) Posts: 1,212	Re: gearing Check for a 3.90 ratio. Probably a hard one to get. 4.11 would be ideal for your application anyway. __________________ 72 2wd Blazer. Its the superbichinest, megacoolinest, superflowinest.

08-16-2006, 07:04 AM	#15
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: gearing Thanks for the help. I'll let yall know what I come up with. Thanks again, Jeremy __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20



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