Gear ratios

[1972GMCsierra4x4]

I'm wanting to regear the axles on my truck so I can get better gas mileage and so I can drive it easier on the highway. I still need it to be low geared enough to pull a trailer though. I was thinking a 3.73 ratio. Suggestions

1972 GMC K2500 Sierra, 350 v8, granny 4 speed, Dana 60 locker rear differential
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[jocko]

WELCOME! Do you know what you have right now? 4.10 or 4.57? Don't forget to consider larger tires into your calculations, they make a big difference.

3.73 a nice ratio for a 4x4, was stock for the K10s (I think) - but that R&P set not common for D60 - here is one Tim found for me once that I saved a link to (I think you sent me this Tim?) http://www.ringpinion.com/b2c/Produc...nd_Pinion_Sets

On the other hand, when you consider you'll need them front and back, you might about break even by installing a heavy duty o/d trans. Beefed 2004R is a possibility, would need an Advanced Adapters tailhousing on the trans to mate to the transfer case I believe. Some folks prefer to relocate the Tcase as an alternative (eliminates the need to move the engine fwd a few inches).

Here are some discussion threads on the o/d trans into a 4x4 swap. Several embedded links also. http://67-72chevytrucks.com/vboard/s...d.php?t=495513

Here's a trans length comparo chart that lolife posted while back also:

[SS Tim]

You really need to go to Gear Vendors site and check out their overdrive units. In your application it would go behind the transfer case and be usable only in 2wd. But the big benefit is that is can be run so as to automatically O/D each gear and give a clutch-less change between gears. It turns your four speed granny into a eight speed transmission. Maintains your current low gear, reduces the drop between gears and completely changes the way your trans will feel to you.
www.gearvendors.com
Also welcome to the board!

Better, specific link
http://www.gearvendors.com/cg2wdt.html

[jocko]

oops, missed the 4-speed granny... Thought it was TH350. Pls disregard the chart in post #2.

[1972GMCsierra4x4]

I'd definetly go with a gear vendors unit if I had the money, but I'm still in high school so I nixed that idea fairly quick. The o/d tranny was appealing too but my truck is numbers matching with just about every option on it you could get back then. My gear ratio now is most likely the 4.57. At least I'm guessing that because the truck is most comfortable running 55-60 mph at about 3000 rpm
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[SS Tim]

Look for a used G/V I see them all the time on CL. In fact, IIRC there is a 456 and G/V combo for sale on SF Bay CL for a $1000. Not exactly what you need but a ggod example. First thing to do is ID your axles and get the real cost of re-gearing them.

[steelhorse]

If you have the room taller tires will do the same thing and you just need a new speedo gear to correct the speedometer.

[PAWS 72]

Dumd ? on my my end,but couldn't he get a 3.08 for his truck? Or is that to much.

[1972GMCsierra4x4]

I would get a 3.08 but idk how we'll that would work for towing. I live on a farm so I need to hook up to a trailer sometimes
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[Ol Blue K20]

How bout some pics of this K2500 please, we like to see the trucks

[1972GMCsierra4x4]

Here she is
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