rear end and gears

chevy kid · 09-18-2005, 07:34 PM

hey guys i dont know much about rear ends or differentials. I am going to but a posi traction rear end but i wanted to know what gears i should run in it. Im going to have 33" pro comps on it and i will be driving my truck both on and off road. it will be a daily driver. could anyone give me a crash course on differentials and what u would run. I am basically a do it yourselfer with a little bit of mechanical abilities. would i be able to chane out the ring and pinions myself?? any help would be appreciated

mrjohnwayne · 09-18-2005, 11:01 PM

yeah you can do it yourself if you have the proper tools and do it correctly. Not that i'm picking at you but with little mechanical abilities i'd let someone who know's how do it. You have to keep a certain tolerance on your back lash (which by itself is not too easy in measuring), meaning trial and error in the way of shimming your pinion gear. You have to check for proper teeth mesh, which isnt to hard but again it is trial and error shimming. As for the actual gear itself if you running 33's, and I'm not a big 4x4 nut so im not 100% sure but i would think that 3:73 or 4:10 setup would handle it. Hope this helps

chevy kid · 09-20-2005, 06:34 PM

yes it does some thank you i think ill try to find a rear end with those gears

chevyguy · 09-22-2005, 02:49 PM

Need more info. What transmission are you running, and what are your primary use of the truck.

HVY84CHVY · 09-27-2005, 10:50 AM

i agree with mrjohnwayne, that you should not do it yourself, i know mechanics that don't even want to attempt gear swaps becasue with improperly shimmed gears you run the risk of demolishing the entire rear end by putting strain on all of the components. Also a 3.73 is a decent all round gear ratio for on and off road performance. As for transmissions, it depends on the application and power that you plan on having, my 84 has about 375 and i run a 700 r4 which is good off road (never had a problem with mine) and good for highway use because of the over drive. if you want to run a high performance motor like mine, then a modified 700r4 from b&m may be the way to go, however this setup does have a hefty price tag.

390FE · 09-27-2005, 02:05 PM

Also with gear swaps it is not necessary but recomended to run the same gear ratio up front as you do out back.

you don't have to do this but don't try to drive on dry pavement in 4x4 either.

Just my 2 pennies for thought.

chevyguy · 09-27-2005, 11:25 PM

390FE, i am really starting to like you.seems we agree on most everything, If I can just get you to come over from the dark side. he he

jobberone · 10-02-2005, 09:24 PM

What kind of truck is it and what kind of rear end to you already have. If you have a 4x4 70s to early 80s Chevy then you probably have a 12 bolt 8.875 rear end where the usual gearing was 3.73. Take the back plate off and inspect everything and count the gears. This url will get you to your rear end: http://www.drivetrain.com/dana44.html#SPECIFICATIONS

There are other ways to get your rear end ratio. Look for numbers and tags hoping they are still there. Lift the rear end and spin the rear wheel one revolution and count the revolutions of the driveshaft...tape helps as well as a partner. You can also plug your rpms, speed into a formula and get it as well. Best to use a GPS for the speed and make sure your tach is right on. Pulling the back plate lets you inspect your gears and you'll know exactly what you have and what kind of posi if any.

Then if you're like me I'd let someone who has done it more than a few times do any work. Maybe you're right where you want to be.

chevyguy · 10-02-2005, 10:35 PM

I have set up several diffs, And sometimes they just fall in place and sometimes they are a motherbear. If you dont want professional help at least find someone who has done this before.A little experience helps alot.

09-18-2005, 07:34 PM	#1
chevy kid Full Member Join Date: Aug 2005 Posts: 23	rear end and gears hey guys i dont know much about rear ends or differentials. I am going to but a posi traction rear end but i wanted to know what gears i should run in it. Im going to have 33" pro comps on it and i will be driving my truck both on and off road. it will be a daily driver. could anyone give me a crash course on differentials and what u would run. I am basically a do it yourselfer with a little bit of mechanical abilities. would i be able to chane out the ring and pinions myself?? any help would be appreciated

09-18-2005, 11:01 PM	#2
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,220	yeah you can do it yourself if you have the proper tools and do it correctly. Not that i'm picking at you but with little mechanical abilities i'd let someone who know's how do it. You have to keep a certain tolerance on your back lash (which by itself is not too easy in measuring), meaning trial and error in the way of shimming your pinion gear. You have to check for proper teeth mesh, which isnt to hard but again it is trial and error shimming. As for the actual gear itself if you running 33's, and I'm not a big 4x4 nut so im not 100% sure but i would think that 3:73 or 4:10 setup would handle it. Hope this helps __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

09-20-2005, 06:34 PM	#3
chevy kid Full Member Join Date: Aug 2005 Posts: 23	thanks yes it does some thank you i think ill try to find a rear end with those gears

09-27-2005, 11:25 PM	#7
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	390FE, i am really starting to like you.seems we agree on most everything, If I can just get you to come over from the dark side. he he __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

10-02-2005, 10:35 PM	#9
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	I have set up several diffs, And sometimes they just fall in place and sometimes they are a motherbear. If you dont want professional help at least find someone who has done this before.A little experience helps alot. __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

09-22-2005, 02:49 PM	#4
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	Need more info. What transmission are you running, and what are your primary use of the truck.

09-27-2005, 10:50 AM	#5
HVY84CHVY Full Member Join Date: Sep 2005 Location: MA Posts: 30	i agree with mrjohnwayne, that you should not do it yourself, i know mechanics that don't even want to attempt gear swaps becasue with improperly shimmed gears you run the risk of demolishing the entire rear end by putting strain on all of the components. Also a 3.73 is a decent all round gear ratio for on and off road performance. As for transmissions, it depends on the application and power that you plan on having, my 84 has about 375 and i run a 700 r4 which is good off road (never had a problem with mine) and good for highway use because of the over drive. if you want to run a high performance motor like mine, then a modified 700r4 from b&m may be the way to go, however this setup does have a hefty price tag.

09-27-2005, 02:05 PM	#6
390FE Senior Member Join Date: Sep 2005 Location: S. NH Posts: 336	Also with gear swaps it is not necessary but recomended to run the same gear ratio up front as you do out back. you don't have to do this but don't try to drive on dry pavement in 4x4 either. Just my 2 pennies for thought.

10-02-2005, 09:24 PM	#8
jobberone Full Member Join Date: Sep 2005 Posts: 21	What kind of truck is it and what kind of rear end to you already have. If you have a 4x4 70s to early 80s Chevy then you probably have a 12 bolt 8.875 rear end where the usual gearing was 3.73. Take the back plate off and inspect everything and count the gears. This url will get you to your rear end: http://www.drivetrain.com/dana44.html#SPECIFICATIONS There are other ways to get your rear end ratio. Look for numbers and tags hoping they are still there. Lift the rear end and spin the rear wheel one revolution and count the revolutions of the driveshaft...tape helps as well as a partner. You can also plug your rpms, speed into a formula and get it as well. Best to use a GPS for the speed and make sure your tach is right on. Pulling the back plate lets you inspect your gears and you'll know exactly what you have and what kind of posi if any. Then if you're like me I'd let someone who has done it more than a few times do any work. Maybe you're right where you want to be.

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