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| | | | Joined: Feb 2004 Posts: 336 Shop Shark | | Shop Shark Joined: Feb 2004 Posts: 336 | I currently have 8 lug 4.10 posi in my 66. I now have the chance to purchase a 6 lug 3.54 posi.
Will this swap give me a significant speed increase? And can I change out the gears to increase the speed even more.
I currently have an NP435 trans (reverse on passenger side) | | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | You can calculate the improvement here: http://www.onlineconversion.com/bigger_tires.htmTo find out if you can get faster gears for any rear axle you first need to know what make and model axle it is, and in some cases what year. Then go to any gear shop, like Randy's Ring & Pinion or a bunch of others, and see what they offer for that model axle. Grigg | | | | | Joined: Feb 2004 Posts: 336 Shop Shark | | Shop Shark Joined: Feb 2004 Posts: 336 | Thnks Gigg nice site
I dont know my trans ratio, its an NP435 | | | | | Joined: Aug 2007 Posts: 67 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2007 Posts: 67 | here is another one i use you dont need all the tranny ratios just the last gear ratio http://www.angelfire.com/fl/procrastination/rear.html
Last edited by coolerthanethan; 02/27/2008 9:36 PM.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | That ratio change represents a 4% change which is very small. | | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | That ratio change represents a 4% change which is very small. Sure it is not a 13.6% change between 4.10 and 3.54? At 65 mph the engine speed drops about 450 rpm, that sounds like a worthwhile swap to me. Grigg | | | | | Joined: Dec 2004 Posts: 1,897 Shop Shark | | Shop Shark Joined: Dec 2004 Posts: 1,897 | Not bad on the numbers, but he would have to derate the truck. The 1/2 ton and 3/4 ton gears don't interchange to my knowledge, so he would have to swap the entire axle. I think a transmission swap would do a little better in the 3/4 ton truck. A 27% overdrive will make an effective drive ratio of 3.00. That isn't to shabby! Use a transmission like the NV4500 and you wn't lose too much in the low range either. | | | | | Joined: Apr 2005 Posts: 54 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2005 Posts: 54 | Billybolt,
I have a 3/4 ton GMC rear at 4:57 and want to swith the pumkin with a newer GM 3/4 4:10. Is the old 66 8-bolt rear pumkin available?
Also considering to use a T-5 tranny with .72 O.D. to go 65 mph at 2764 rpm (with current 4:57 rear).
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