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Old 04-17-2014, 02:50 AM   #1
Jimbo68
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Rear differential question!!!

I just bought a 65 chevy c10 long bed the other day, and it's got a 350 with a four speed on the floor. When I'm running 55-60 mph my engines turning around 3500rpm which I know is high but what would be a good rear gear that would help lower those rpm's and make for better cruising?
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Old 04-17-2014, 06:37 AM   #2
PGSigns
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Re: Rear differential question!!!

For just a cruiser I would look for a 308. A taller tire helps also.
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Old 04-17-2014, 06:53 AM   #3
Jimbo68
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Re: Rear differential question!!!

Would the 3.08 keep the rpms down where they should be with the four speed at like 60mph?
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Old 04-17-2014, 07:56 AM   #4
Clyde65
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Re: Rear differential question!!!

Look at this...
http://www.summitracing.com/expertad...tio-calculator

plug in your info and see what the RPM would be with 3.08's and ( I believe you have) 4.10.

Good luck. Any chance you will put an OD tranny in it?
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Old 04-17-2014, 08:44 AM   #5
kieth
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Re: Rear differential question!!!

Quote:
Originally Posted by Jimbo68 View Post
I just bought a 65 chevy c10 long bed the other day, and it's got a 350 with a four speed on the floor. When I'm running 55-60 mph my engines turning around 3500rpm which I know is high but what would be a good rear gear that would help lower those rpm's and make for better cruising?

measure the height of you rear tire from ground to top of tire, then look at the attached charts, they should tell you what you need to know...

TORQUETOGROUND_Master_r.pdf


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Old 04-17-2014, 01:29 PM   #6
jtrichard
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Re: Rear differential question!!!

you talking a granny low 4spd? I have a 76 blazer with 307s and granny 4spd it is great down hill in a hurricane.... flat ground is not bad ...a little tricky to get rolling at first and a dog on the hills....only gets worse if you have tall tires...... I would stick in the 3.50 range
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Old 04-17-2014, 06:45 PM   #7
jdp
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Re: Rear differential question!!!

Quote:
Originally Posted by Jimbo68 View Post
I just bought a 65 chevy c10 long bed the other day, and it's got a 350 with a four speed on the floor. When I'm running 55-60 mph my engines turning around 3500rpm which I know is high but what would be a good rear gear that would help lower those rpm's and make for better cruising?
I'm in nearly the exact same boat: same year, long bed, 350 sbc, 4 on the floor with granny. Putting another transmission in soon. Good luck.
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Old 04-17-2014, 07:44 PM   #8
Jimbo68
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Re: Rear differential question!!!

I mean how hard would it be to just do a tranny swap from the 4 speed to a 700r4?
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