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Old 08-22-2019, 10:41 PM   #1
ecbert
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Ring and pinion

Does anyone know where I can get a higher (lower numerically) ring and pinion for my 70 GMC 5500? either new or used, whole take out third member would work. I believe it has the H150 / H170 two speed rear, currently it has the 6.50:1 ratio and I'd like to go to the 4.83:1 ratio.
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Old 08-23-2019, 03:47 AM   #2
Pvmt-Pndr
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Re: Ring and pinion

LKQ is where I've been able to find gear sets or 3rd member for my rear end. There are a couple of other places that have found too but it seems like LKQ bought all of them anyways. A phone call to them should get you whatever you want if it's out there for sale. In a 24 hour period they called me back with 3 different options
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Old 08-23-2019, 08:57 AM   #3
ecbert
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Re: Ring and pinion

Pvmt-Pndr, thank you for the reply. I actually have an inquiry into them already and I did manage to find some NOS stuff out there from various suppliers but they wanted over $1g just for the ring and pinion. For that price I can get a complete newer Eaton rear but that's not the way I want to go.
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Old 08-23-2019, 09:01 AM   #4
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Re: Ring and pinion

I'm in the same boat as you are. I was quoted around the same price for 4:88s and 4:56s all between 1000-1400 if I recall correctly. That will probably be the last big thing I do. Once I rebuild my engine I'll be able to determine which of the two I want.
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Old 08-23-2019, 09:36 AM   #5
ecbert
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Re: Ring and pinion

I didn't even see the 4.56's in the GM book, only the 4.88's (I thought the book said 4.83's but I could be wrong). Can you send me a link as to where you found the parts? Changing from 6.50's to 4.88's or 4.56's would be like adding an overdrive transmission! I also need to rebuild (tank) my 366, I have found a 427TD block and I plan on using that in the future.

Thanks for your advice / replies.
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1969 369 Nova
1967 Chevelle SS 396
1970 GMC 5500
1991 V3500 Single RR Wheel Gen 6 496 / 4L80E
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Old 08-23-2019, 09:51 AM   #6
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Re: Ring and pinion

The 4:56 and 4:88s i mentioned were for my rear end, I have a 17221. I currently have 6:50/8:87 low.

That's exactly why I want suck a high gear but before I pull the trigger I need to make sure I'll have the power to make up whatever drop in rpm they will create.

I highly recommend you find a gear calculator and punch in all the info to it to see if you'll have the power for the split too. I wrote out 4 different gears. 6:50 (for direct comparison), 5:29 (a member has a set for a great price), 4:88s and 4:56. Then I laid them all out on a table to see where I would be and how many mph split there was between gears. I also noted where 60/65/70 mph was and what rpm I would be at so I can ride the torque curve of the engine while cruising. I found that 4:88s puts me in the happy spot in 5H while 4:56 drops the rpms low enough to act as an OD and I can always down shift. The biggest gap I believe was 13 mph which may be a little too much but I'm not sure. That's why I'm not wanting to buy gears until I rebuild the engine. Since the day I bought the truck something wasn't right and now I know I lost the cam and have low compression in one cylinder.
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Old 08-23-2019, 10:29 AM   #7
sweetk30
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Re: Ring and pinion

http://www.grimmjeeper.com/gears.html

good calculator here for the offroad guys . but can be used a lot with others . if your tans is not listed just type in the #'s and it will compute from there .
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Old 08-23-2019, 08:41 PM   #8
ecbert
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Re: Ring and pinion

I already made an RPM calculator in Excel, the TD 427 that I have it going to make 3x the power that my current 366 does, without much difficulty. I don't use the truck for hauling anymore so I don't really need the low gear ratio. I found some gear sets online but they are not high enough, anyone have any sources?
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2011 12 Passenger G3500
1969 369 Nova
1967 Chevelle SS 396
1970 GMC 5500
1991 V3500 Single RR Wheel Gen 6 496 / 4L80E
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Old 08-23-2019, 08:48 PM   #9
Pvmt-Pndr
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Re: Ring and pinion

You may be better off swapping the whole rear end.
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Old 08-23-2019, 10:18 PM   #10
sweetk30
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Re: Ring and pinion

just cause you go gear ratio for better rpm and more speed dont forget these old trucks have old brake system designs and steering also . up grade one watch out for the other .

as said maybe swap to newer axle pair and get better brakes and ratio all in 1 .
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77-k30lb BIG truck build .
87-k30lb budget beater build .
85-k30lb the plow machine build .
85-c10sb summer fun toy .
-----------------------------
HOLLEY SNIPER efi = worst case of p.i.t.a i ever had .

EDELBROCK pro flo 4 = best deal going so far . love my setup works great.
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