Need rearend advice - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dave3156 · 12-20-2005, 07:29 AM

I just heard from the repair shop that the rearend on my 1970 Stepside has gone out. I thought this might be a good time to change gears. It has a 350 engine with some performance upgrades (Performer rpm manifold, Edelbrock #1407 carb, headers, dual 3" exhaust), and a Saginaw 3 speed transmission. I'm not sure what gears were in the truck. The mechanic thought they were 3:23 gears. He pulled the hub and counted the gears. Does anyone have an idea of what would be the best gears to run. I drive it mostly on weekends and short trips. Gas mileage is not a factor, performance is. I'm considering 3:73 gears. The tire size is 295/55/15. Any advice is welcome. Thanks.

Tx Firefighter · 12-20-2005, 07:34 AM

I wouldn't ever spend much money to repair a rearend in one of these trucks. A six lug rearend is super easy to find. I have given away 3.73 6 lug rearends before. Everyone swaps to 5 lug, so 6'ers are all the time turning up needing a new home.

BTW, I doubt the 3.23 gears. It should be either 3.73 or 3.08.

If you're after performance and not mileage, definitely go 3.73.

355 · 12-20-2005, 08:47 AM

I agree with TX it is a 3.07 or a 3.73. If you install a 3.73 and had a 3.07 it will feel like you just added 50# of torque, but your top end will be limited by engine rpm. If you have a modified cam you need to match your rearend ratio, and tire size to when your cam is coming in. If gas milage is no problem I would find an Eaton LSD and 3.73 gears. Now is the time to go 5 lug and upgrade to front disc. My to cents.

dave3156 · 12-20-2005, 10:44 AM

After further discussion I found out the rearend is a 3:07 ratio. The axle is already five lug, as is the front axle, and I already have disc brakes in the front.

Old Yeller 1970 · 12-20-2005, 11:17 AM

I'd drop in the 3.73's and put in a limited slip or locker while you are at it.

67chevemall · 12-20-2005, 11:25 AM

Quote:

Originally Posted by dave3156

After further discussion I found out the rearend is a 3:07 ratio. The axle is already five lug, as is the front axle, and I already have disc brakes in the front.

Your in the loop! Go for the posi! 3:73 or 4:11

355 · 12-20-2005, 11:53 AM

If you go 4.11 you will probably have to go to the next size carrier due to gear offset. Your highway speed will be crap and you will not be able to hear your radio due to engine rpms, but that all depends on what is pulling your trigger.

12-20-2005, 07:34 AM	#2
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Need rearend advice I wouldn't ever spend much money to repair a rearend in one of these trucks. A six lug rearend is super easy to find. I have given away 3.73 6 lug rearends before. Everyone swaps to 5 lug, so 6'ers are all the time turning up needing a new home. BTW, I doubt the 3.23 gears. It should be either 3.73 or 3.08. If you're after performance and not mileage, definitely go 3.73. __________________ I'm on the Instagram- @Gearhead_Kevin

12-20-2005, 08:47 AM	#3
355 Registered User Join Date: May 2005 Location: South Mississippi Posts: 81	Re: Need rearend advice I agree with TX it is a 3.07 or a 3.73. If you install a 3.73 and had a 3.07 it will feel like you just added 50# of torque, but your top end will be limited by engine rpm. If you have a modified cam you need to match your rearend ratio, and tire size to when your cam is coming in. If gas milage is no problem I would find an Eaton LSD and 3.73 gears. Now is the time to go 5 lug and upgrade to front disc. My to cents. __________________ 1969 C10 Long Step,355,700r4w/lockup, HEI,Weiand,750 Performer,1.6 rockers,Camel Humps,Comp 262Extreme,Hedman,2 1/2"pipes, tele/tilt,SunRoof,ps,Disc pb,ac,Cragar,eaton,Corvette style roll pan, Bowtie louvered tail gate,lowered 2/2.

12-20-2005, 10:44 AM	#4
dave3156 Registered User Join Date: Mar 2004 Location: St. Louis, MO Posts: 336	Re: Need rearend advice After further discussion I found out the rearend is a 3:07 ratio. The axle is already five lug, as is the front axle, and I already have disc brakes in the front.

12-20-2005, 11:17 AM	#5
Old Yeller 1970 DON'T TREAD ON ME Join Date: May 2005 Location: Crosby County, TX Posts: 989	Re: Need rearend advice I'd drop in the 3.73's and put in a limited slip or locker while you are at it. __________________ Old Yeller

12-20-2005, 11:53 AM	#7
355 Registered User Join Date: May 2005 Location: South Mississippi Posts: 81	Re: Need rearend advice If you go 4.11 you will probably have to go to the next size carrier due to gear offset. Your highway speed will be crap and you will not be able to hear your radio due to engine rpms, but that all depends on what is pulling your trigger. __________________ 1969 C10 Long Step,355,700r4w/lockup, HEI,Weiand,750 Performer,1.6 rockers,Camel Humps,Comp 262Extreme,Hedman,2 1/2"pipes, tele/tilt,SunRoof,ps,Disc pb,ac,Cragar,eaton,Corvette style roll pan, Bowtie louvered tail gate,lowered 2/2.

12-20-2005, 07:29 AM	#1
dave3156 Registered User Join Date: Mar 2004 Location: St. Louis, MO Posts: 336	Need rearend advice I just heard from the repair shop that the rearend on my 1970 Stepside has gone out. I thought this might be a good time to change gears. It has a 350 engine with some performance upgrades (Performer rpm manifold, Edelbrock #1407 carb, headers, dual 3" exhaust), and a Saginaw 3 speed transmission. I'm not sure what gears were in the truck. The mechanic thought they were 3:23 gears. He pulled the hub and counted the gears. Does anyone have an idea of what would be the best gears to run. I drive it mostly on weekends and short trips. Gas mileage is not a factor, performance is. I'm considering 3:73 gears. The tire size is 295/55/15. Any advice is welcome. Thanks. Last edited by dave3156; 12-20-2005 at 07:34 AM.



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