Total newbie rear end question

[harley]

I was researching ring and pinion gears for my newly aquired 63 SWB and realize I am just about clueless

Current gearing is 4.11 and I want to go to about a 3.38 give or take, open to suggestions also.

Anyway I finally called Randy's Ring and Pinion for a quote and that's when I realized I am clueless. He asked if it was a 12 bolt rear and whether the gears drop from the front or rear. Uhhhhhhh, I dunno

There are 12 bolts on the rear end but how do I tell if drops from the front or rear?

Pardon my cluelessness

[Tim64]

It might be easier to go with a overdrive transmission. If highway driving is what you're looking for. I've been told changing rearend gears can be quite tricky.
Tim

[Tx Firefighter]

You should be able to turn up a highway geared complete rearend out of a 63-70 model truck. This would keep your six lug bolt pattern wheels and be super easy and cheap. A lot of the trucks came with 3.08 gears. My 64 has them stock. I know it's not the exact ratio you're wanting, but they cruise real nice and swapping a complete rearend is cake compared to going inside of one and swapping the r&p.

[harley]

I'm not set on the 3.38 ratio at all. It was just the only gear set Randy's had to offer.

How do I tell if my rear end unloads from the front or rear?

I'd be open to a total rear end swap if I could find a suitable candidate.

[Tx Firefighter]

A shortbed will have rear loading gearset. The heavier trucks, like 3/4 and 1 tons used a drop out centersection that comes out the front of the differential.

The 67-70 model guys pretty much give 6 lug rear ends away. They all want to convert to the later model 5 lug stuff instead.

I've sold a many of them for 50 or 100 bucks. Just search out a 1/2 ton rearend from a pre 1970 model truck that has the desired ratio. They typically came in 3.08 and 3.73 gearing.

[fuelpump]

I just bought a 3.38 from Randy's to replace my 3.90. Here is a post that might help you.
http://67-72chevytrucks.com/vboard/s...d.php?t=264941

[harley]

Thanks.

Did you do the swap yet? How much of an inprovement did you see?

[fuelpump]

Originally Posted by harley

Thanks.

Did you do the swap yet? How much of an inprovement did you see?

No I haven't put it in yet.

[Captainfab]

Originally Posted by harley

I was researching ring and pinion gears for my newly aquired 63 SWB and realize I am just about clueless

Current gearing is 4.11 and I want to go to about a 3.38 give or take, open to suggestions also.

Anyway I finally called Randy's Ring and Pinion for a quote and that's when I realized I am clueless. He asked if it was a 12 bolt rear and whether the gears drop from the front or rear. Uhhhhhhh, I dunno

There are 12 bolts on the rear end but how do I tell if drops from the front or rear?

Pardon my cluelessness

1963 was the first year for the 12 bolt rear end, so assuming yours hasn't been changed, you have a 12 bolt. Of course this is assuming you do have a 1/2 ton. Having a 12 bolt gives you many more options with gear sets and other upgrades. One thing to be aware of is the 12 bolts from '63-'65 have coarse splined axles (10 spline IIRC) instead of 30 spline like the '66-'79 12 bolts. This would only be an issue when changing the carrier to say a limited slip or posi. Also when changing complete rear ends make sure the one you are switching to is of the same width, or a useable width for you. In 1971 GM switched to 5 lugs, and those rear ends are 1 1/2" wider than the one you currently have. I'm not sure on the width of the '69 & '70 rears, but the '63-'68's will be the same and have 6 lugs.

Just a FYI regarding gears and RPM's. In my '66 Burb I have 3.42 gears and I'm running 275/60-15 tires and at about 65 mph the engine is turning 3200 rpms

The earlier 1/2 ton rear ends which were used up through '62 had a round rear cover with 10 bolts and a drop out 3rd member on the front side that also was bolted to the housing with 10 bolts.

[Iron-Butt]

I went to a 308 rear end out of a 1972 truck so I could have the 5 lug set up. With the 454 / 400 auto it cruises at high speeds with low rpm all day long.

[mateo1279]

A related question on rear end swaps:

When looking for a swap candidate, how does one determine the ratio? Is there an imprint or code stamped somewhere, or do you have to pull the cover and do some math?

hope this isn't too far off topic..

-matt

[Captainfab]

Originally Posted by mateo1279

A related question on rear end swaps:

When looking for a swap candidate, how does one determine the ratio? Is there an imprint or code stamped somewhere, or do you have to pull the cover and do some math?

hope this isn't too far off topic..

-matt

The only way I know of to be positive is to pull the cover. I myself have never seen any codes on the differential.

[mateo1279]

Once the cover is pulled, how does one go from there?

-Matt

PS:Sorry for throwing in q's like this on someone else's thread...

[Captainfab]

Originally Posted by mateo1279

Once the cover is pulled, how does one go from there?

-Matt

PS:Sorry for throwing in q's like this on someone else's thread...

Look on the outside edge of the ring gear for some numbers. There will be the part number, the date, and the number of teeth for both the ring gear and the pinion gear. they will be something like 11 41. that's 11 teeth on the pinion and 41 teeth on the ring gear. Divide 11 into 41 which is 3.7272, so that would be a 3.73 gear ratio. Let me know if you need any more help.