what rear end ratio for 327/Powerglide

[Russ65C10]

I am pretty sure the 3.73's were one of the more common gear sets so it should be easy to find one in 71/72 or any other year for that matter. They're about as good a all round as you could've ordered in these old truck. I both my 66 & 65 came standard with them and they're still pretty common in today's trucks. If your looking for 5 lug rear end I think you need to go newer than 72 but I could be wrong.

Do you know what you currently have in the truck?

[likaroc13]

Originally Posted by Russ65C10

I am pretty sure the 3.73's were one of the more common gear sets so it should be easy to find one in 71/72 or any other year for that matter. They're about as good a all round as you could've ordered in these old truck. I both my 66 & 65 came standard with them and they're still pretty common in today's trucks. If your looking for 5 lug rear end I think you need to go newer than 72 but I could be wrong.

Do you know what you currently have in the truck?

that's what i thought...not sure what mine has for sure...it's low though, so i'm figuring 4.11's...with the '71/72 rear, you can just swap it in...it's a tad wider but still utilizes the trailing arms without modification if i'm not mistaken...'73-87 is same width as 71/72, but you would have to cut off & mount perches for the trailing arms

[Captainfab]

I would suggest pulling the rear cover and seeing just what you do have before you get excited about finding another rear end.

[fleetsidelarry]

For years, I drove my '66 (with a th375) with what I would have sworn was a 4:11 because of how wound up it was at 55, when I checked it, it turned out to be a 3:73. So, as Captainfab suggested, you might want to find out what you have as a starting point. You can also check the ratio without removing the cover.

I now have a 3:08 (or is that 3:07) with my 700r and couldn't be happier. Around town I can keep it in 3rd (which is 1:1 remember) for anything up to 45 (about 2000 rpm), on the highway 4th (OD) is perfect and, when I want to keep up with the Interstate bunch, I reach down and throw the manual lockup switch. The 700r's low first gear gets you launched just fine, I can still light up a tire if I want BUT, of course, it doesn't accelerate like a 3:73.

BTW, the 71-72 rears ARE 5 bolt

[likaroc13]

Originally Posted by Captainfab

I would suggest pulling the rear cover and seeing just what you do have before you get excited about finding another rear end.

"To check rear end ratio jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers and 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading."

i followed this trick today, & it seems that it very well might be 3.73's...i'll know for sure when i get the rear serviced...even so, wouldn't it still be cheaper to find a donor '71/72 rear? i looked at CPP & Early Classic, & those 5-lug axle conversions aren't cheap...not to mention, wouldn't the rear track width be shorter than the front if i keep the '66 rear & switch to 73-87 front crossmember?