What options available to change gears in 66 3/4 rear? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ScottH** · 01-14-2010, 08:36 PM

Looking at a 66 3/4 ton truck that I'm pretty sure has 4:57 ratio.
I'd like to change it to 4:10 gear and was wondering what I could use as a donor. Could I swap in a rear from a 72 3/4 4x4 for example? Or what year(s) would be suitable to remove the gears from to install in the original rear?

Any suggestions or info is very much appreciated.

Thanks.

Scott

62gmc910 · 01-14-2010, 08:45 PM

If its a chevy third member diff then you might find a later truck with a 4.10 tthirdmember diff .If you have to change the whole axle out a 73-87 full floater 14 bolt would be the way i would go lots of parts and a good selection of gears 3.23 to 5.13 I believe

**Captainfab** · 01-15-2010, 01:22 AM

The '71-'72 3/4 tons came with Dana 60 rear differentials which had 3.54 to 4.10 gears available. They may have been available in other years, but these years are where I see them most often. These would be a bolt in swap. If you can't find one of the Dana 60's then I would suggest what 62gmc910 suggested which is a '73 and up full floating 14 bolt. The 14 bolt would require some cutting and welding to bolt it under your truck. Both have a great aftermarket support as well.

**ScottH** · 01-15-2010, 11:25 AM

Thanks guys. Would u know what the stock ratio would be on a 70 sub 3/4 auto 4x4 HO52 no spin rear?

**ScottH** · 01-15-2010, 03:20 PM

Also can anyone tell me what I could use as a donor for just the ring/pinion for this swap? The truck is all original so I'd rather keep the original setup, just change out the gears. Perhaps they sell new gears to fit this rear?

Thanks.

62gmc910 · 01-15-2010, 03:33 PM

what axle do you have now
is the truck a chev or gmc?
there is a section above for ID ing by vin number

**ScottH** · 01-15-2010, 05:25 PM

It's a 66 GMC which from what I've read comes with a 4:57 stock
I don't have it yet, just trying to figure out what I want to do when I get it.

Thanks.

mikie 1954 · 01-16-2010, 12:06 AM

I have a 64 gmc 3/4 ton with a dana 60 that i had the gears changed in about 8 months ago.Like you i thouht it had 456's in it but it turned out to be 4-10's. I had 353's put in & have been very happy with it every since.One thing that i had to do was change the yok , the old one had less splins. SOmake sure whitch you have when you order your new gears & get the right one. mikie:gmc2

**Captainfab** · 01-16-2010, 02:20 AM

There are no new gears available for the Eaton HO52 differential. You will have to find a good used set or the entire 3rd member. The HO52 was used from the early 50's up thru '72 (?) There are quite a few guys that would like to find a set of 4.10's for the HO52.

Quote:

Originally Posted by ScottH

Also can anyone tell me what I could use as a donor for just the ring/pinion for this swap? The truck is all original so I'd rather keep the original setup, just change out the gears. Perhaps they sell new gears to fit this rear?

Thanks.

64bigblock · 01-27-2010, 02:39 AM

give me a call i just went through my stock 64 4x4 for ideas 608 485 0992 Shane
ive chaged the gears 3rd member newer ffont axle id id be more than happy to help

01-14-2010, 08:36 PM	#1
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	What options available to change gears in 66 3/4 rear? Looking at a 66 3/4 ton truck that I'm pretty sure has 4:57 ratio. I'd like to change it to 4:10 gear and was wondering what I could use as a donor. Could I swap in a rear from a 72 3/4 4x4 for example? Or what year(s) would be suitable to remove the gears from to install in the original rear? Any suggestions or info is very much appreciated. Thanks. Scott __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

01-14-2010, 08:45 PM	#2
62gmc910 Registered User Join Date: Nov 2009 Location: Cremona AB Canada Posts: 370	Re: What options available to change gears in 66 3/4 rear? If its a chevy third member diff then you might find a later truck with a 4.10 tthirdmember diff .If you have to change the whole axle out a 73-87 full floater 14 bolt would be the way i would go lots of parts and a good selection of gears 3.23 to 5.13 I believe __________________ 62 GMC 910 short fleetside 454 super t10 14 bolt w/gov lock 70s c20 front discs (built in the 80s) 65 GMC 930 dualwheel 292 4spd all origonal 39k mi(my sons truck) 63 GMC 950 camperized school bus, (Gus the bus) 350 4speed 2 speed rear 64 GMC 950 "spare" bus 283? 4speed detroit locker 53 GMC 1ton dual wheel bus 78 GMC c25 short course off road race truck(son's truck) 355 th400 14 bolt (www.wheel2wheel.ca) 88 Peterbilt 379 longhood (hauls race truck)

01-15-2010, 01:22 AM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: What options available to change gears in 66 3/4 rear? The '71-'72 3/4 tons came with Dana 60 rear differentials which had 3.54 to 4.10 gears available. They may have been available in other years, but these years are where I see them most often. These would be a bolt in swap. If you can't find one of the Dana 60's then I would suggest what 62gmc910 suggested which is a '73 and up full floating 14 bolt. The 14 bolt would require some cutting and welding to bolt it under your truck. Both have a great aftermarket support as well. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE Last edited by Captainfab; 01-15-2010 at 01:23 AM.

01-15-2010, 11:25 AM	#4
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	Re: What options available to change gears in 66 3/4 rear? Thanks guys. Would u know what the stock ratio would be on a 70 sub 3/4 auto 4x4 HO52 no spin rear? __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon Last edited by ScottH; 01-15-2010 at 01:17 PM.

01-15-2010, 03:20 PM	#5
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	Re: What options available to change gears in 66 3/4 rear? Also can anyone tell me what I could use as a donor for just the ring/pinion for this swap? The truck is all original so I'd rather keep the original setup, just change out the gears. Perhaps they sell new gears to fit this rear? Thanks. __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

01-15-2010, 03:33 PM	#6
62gmc910 Registered User Join Date: Nov 2009 Location: Cremona AB Canada Posts: 370	Re: What options available to change gears in 66 3/4 rear? what axle do you have now is the truck a chev or gmc? there is a section above for ID ing by vin number __________________ 62 GMC 910 short fleetside 454 super t10 14 bolt w/gov lock 70s c20 front discs (built in the 80s) 65 GMC 930 dualwheel 292 4spd all origonal 39k mi(my sons truck) 63 GMC 950 camperized school bus, (Gus the bus) 350 4speed 2 speed rear 64 GMC 950 "spare" bus 283? 4speed detroit locker 53 GMC 1ton dual wheel bus 78 GMC c25 short course off road race truck(son's truck) 355 th400 14 bolt (www.wheel2wheel.ca) 88 Peterbilt 379 longhood (hauls race truck) Last edited by 62gmc910; 01-15-2010 at 03:40 PM.

01-15-2010, 05:25 PM	#7
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	Re: What options available to change gears in 66 3/4 rear? It's a 66 GMC which from what I've read comes with a 4:57 stock I don't have it yet, just trying to figure out what I want to do when I get it. Thanks. __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

01-16-2010, 12:06 AM	#8
mikie 1954 Registered User Join Date: May 2009 Location: caliente ca. Posts: 297	Re: What options available to change gears in 66 3/4 rear? I have a 64 gmc 3/4 ton with a dana 60 that i had the gears changed in about 8 months ago.Like you i thouht it had 456's in it but it turned out to be 4-10's. I had 353's put in & have been very happy with it every since.One thing that i had to do was change the yok , the old one had less splins. SOmake sure whitch you have when you order your new gears & get the right one. mikie:gmc2

01-27-2010, 02:39 AM	#10
64bigblock Registered User Join Date: Jan 2010 Location: monona, iowa Posts: 9	Re: What options available to change gears in 66 3/4 rear? give me a call i just went through my stock 64 4x4 for ideas 608 485 0992 Shane ive chaged the gears 3rd member newer ffont axle id id be more than happy to help



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