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Guys I see people using blazer rearends from the 80's yet the ones I have measured were wider than my 1952 1/2 ton 62" hub to hub original. Could someone please measure there newer 6 lug 4x4 rearend to see if it is wider? Does the wider rearend work okay? I am going to use 215/85r/16 tires. I am having a heck of a time trying to find a rearend that fits. There are a lot of 4x4 six lug rearends here but they are around 65". When I have posted before I am refered to a rearend width web page in the tech section. What is confusing me is every 4x4 rearend I have measured from a 70's, 80's 4x4 truck has been wide. But is it too wide or will it work? Thanks, Wayne

if your truck is still together, measure to see if you have room to move your wheels 1 1/2 inches out. them fenders are pretty forgiving. you could also try finding a blue chip gmc (55-59) they had about a 62 inch 6 lug dana rear.

My truck is all tore apart so I can not measure. If anybody has installed a newer rearend that fits could they please measure from outside of hub to hub? If it fits it will give me another option of finding a rearend that fits my '52. Thanks, Wayne

When I went to an open drive line in my '51 I tried a 62" wide (mount surface to mount surface) from under a caprice. Since the new diff was 5 bolt I used newer steel rims. Since I was going with wider tires, I needed wider rims too. So, when I slapped the tires on the new diff they hit the frame.

That is when I figured out the backspacing on the newer rims ain't the same as the older ones, plus my rims and tires were wider than the stock ones.

See, the mounting surface on the stock tires was smack in the middle of the rim, so the distance from the mounting surface to the frame-side edge of the rim was like 3" or less. With wider tires you need wider rims. Plus, newer rims have the mount surface about 3/4 of the way to the outside of the rim. So, with my 7.5" rims, 3/4 of the width was on the frame side of the mounting surface.

I ended up using a 65" wide rear end. (from backing plate to backing plate.)

So, to sort of answer your question, no one but you can figure out how wide a rear axel you need because only you knows the backspacing and width of your new tires. With stock tires there is room for an extra 1 1/2" on either side so a 65" diff should be okay. With wider rims, or modern rims, a 62" diff might be a problem.

Thanks NM51,

I plan on using a 6" modern rim and running 215/85R/16 tires. It may be a 65" 4x4 rearend may work after all. Have a great day, Wayne

May I make a suggestion? Check with your rim supplier to make sure you can get a 6 lug rim with the proper backspacing in a 16" diameter with your choice of tire size. A 65" diff may present problems.

I just went through the process with my truck conversion to an open drive and suggest you look ahead to a front disc conversion that you might want in the future and rim problems you might encounter.

My truck stock diff was 62" from wheel mounting surface to mounting surface so logically I went yard hopping for that width. That width would require me to use a 4" backspacing on an 8" wide rim to center my tire in the rear wheel well. On your setup, with a 6" rim on 62" you would use a 3" backspacing. No problems so far. However, add another 1-1/2" to your diff width (for 65") and you'd need 4-1/2" backspacing on a 16X6" rim. Hopefully, you'll have better luck than I did on finding this rim configuration.

Ultimately, I had to shift gears and take a look at some other configurations and went with a 62" diff (3.08 R&P)from a 70-80"s Camaro, 5 lug w/15X8 rims with 4" backspacing and a fat BFG 255/70/15 that are 29"tall. This centered the tire width-wise in the rear wheel well.

Have you thought about the front end? If you're even remotely thinking about a disc upgrade on a "driver" the 5 lug conversion is IMHO a much simpler/cheaper way to go. The 5 lug uses Camaro rotors and discs. The 6 lug uses your old hubs minus the drums and you'll wind up springing $120. for the replacement roller wheel bearings. The Camaro bearings from CPP are $30. and you can get all the replacement parts from your local parts house.

I'm running a 15X7" w/4" back spacing on this front setup with a BFG 235/70/15 needing no wheel spacers and clears the stock tie rods on the inside by 1". Upgraded tie rods would give you even more clearance between the tire.

The only downside of going from 6 to 5 lug is that you probably aren't going to be able to use the stock hubcap setup.

You can duplicate the tire height, have the tire/rims centered properly and have fewer hoops to jump through with the 5 lug conversion but it's totally up to the individual which way he decides to go. I just wanted to show you an option that was viable, looks good and is being driven on a daily basis.

I went through 2 months of trial and error chasing diffs and rims to get it right and hope that this may save you some of the headaches.

Dave

Dave,
Your truck looks great. You did a nice job on the ol' girl. Thanks for the response. Yes, I am going with front disc brakes and have been waiting until I know what bolt pattern rearend I pick up. The yards here vary a lot in pricing from $700 for a rearend to $100 at a mom and pop yard. Unfortunately they do not have a rearend that fits right now but a 60" Chevelle rearend may become available. I am looking for a 3.08 up to a 3.43 ratio to go behind a 283/th350 set up. My truck is all torn down and I am getting a little antsy to start putting her back together again. I will keep looking. Thanks, Wayne

I used a 1977 4x4 suburban heavy duty 12 bolt- 3.40:1 ratio and a T5 hybrid. just about any 10 or 12 bolt should fit. do you want 5 or 6 lug wheels? and ratio.


Want to know about swapping out a rear end.
and what to use Here's food for thought.... on 50’s chevy’s By: Jim Forbes


The 82-newer Camaros are wider than the older ones, so you should stick with the 70-81 models. The 75-79 Nova uses the same rear as these older Camaros, I believe. The 68-74 Nova chassis is the same as a 67-69 Camaro; the 75-79 Nova chassis is the same as the 70-81 Camaro. The 82-newer Camaros used the small 7.5" rearend design that the 78-newer Malibu/Monte Carlo/regal/cutlass etc used, but it's quite a bit wider. Some of the 82-newer Camaros used different rearends, such as the Dana 44, and some wierd Australian rearend. Of course, if you want to make sure, get out your tape measure and check yourself! I may be wrong.
Here's another one from Jim on the subject---- There are lots of rearends available! Some fit better than others. For 6 lug rearends, the 64-69 1/2 ton 2wd Chevy (and some GMC) trucks have a 12 bolt rear, about 60-61" wide (I measure them where the wheels bolt on). The 70 2wd and 70-81 4wd have a 6 lug 12 bolt that is a couple inches wider, but will fit under a Advanced Design /Task Force truck as long as you don't get too wild with wheel/tire width. The 12 bolt truck rearends from the 60s usually had 3.70 gears, which is a bit much for extended highway driving at 75 mph. You can swap the differential carrier and ring/pinion gears from a later TRUCK or VAN 12 bolt, the 70s trucks usually had 3.08 or 3.40 gears. Of course, you'll need to know how to set up ring/pinion gears, bearing preload, and all that other neat stuff to do this. These 60s truck 12 bolt rearends are from coil spring trucks, so the perches are in the wrong place, and they have some extra stuff on the housing for a panhard bar, which you won't need with leaf springs. Most 60s GMC trucks, and some Chevys, had Dana 44 or Dana 60 rearends, and leaf springs. These rearends are 6 lug, about 60" wide, and will bolt into a Task Force truck (with some fudging, the perches are about 1/2" too far apart). The brakes use different parking brake cables, which is a problem, and the drums have a different offset. Gear ratios range from 3.21 to 3.92 normally, the 3.21 is found behind some GMC V-6 engines, and is a nice ratio for an old truck. The Dana 44 uses a standard Chevy 1310 yoke, but the Dana 60 uses a heavy duty yoke, which takes a larger 1350 series ujoint. A similar Dana 40 rearend was availalbe as an option in 59 Chevy trucks, equipped with positraction...rare, and with a 3.92 ratio. I have one of these rearends, it was in my extended cab truck...I'm saving it for when I build a race truck (one of these years).
The 71 and newer 2wd trucks use a 5 lug 5" bolt pattern, same as the 71-76 full size cars. There is not much available in the way of matching front brake rotors that will fit an old truck, so this rearend is not too popular a swap, unless you get the 70-up 4wd 6 lug axles. Chevy also used 10 bolt rearends in lots of cars, in varying widths. A common one is the 61" wide 70s vintage Camaro/Chevelle/Nova (and clones) 8.5" rearend. In Camaros/Novas it has leaf springs, but the perches won't work with old truck springs. In Chevelles, it has coil springs, with lots of extra brackets to cut off, and the cast in mounting "eyes" on top, where the upper control arm bushings fit. Wheel bolt pattern is 4.75", and there are front disk brake kits available to match, or you can use the 53-54 car front hubs/drums on the original 50s truck brakes, to get the same bolt pattern front/rear. This is a good rearend for using in an old truck, the ratios are commonly 2.73-3.36, with higher gears available. The axle shafts are usually worn out in these things, so check them (pull the cover, lockpin, and C clips out to get them loose) where they ride in the wheel bearings...before buying the rearend! The 55-57 Chevy car rearend is almost a bolt in, the perches need to be relocated to the top of the housing though. It has the 4.75" bolt pattern, and ratios are usually 3.55-3.73, but sometimes you'll find a 3.36. The 78-88 mid size GM cars use a 7.5" 10 bolt, which is about 58/5" wide. This rearend would work well in an early (older than 47) truck, but it is quite light duty. Ratios are usually 2.29-3.23, which means you want some torque in the engine to pull it...but rpm will be low. This is a coil spring rearend, with all the mounting brackets that need to be cut off. The Ford 8" and 9" rearends come in a whole bunch of varieties, and only a few are usefull in oletrucks. The late 50s full size cars have a nice one, but it's not easy to find brake hardware, drum, etc anymore. The mid 60s midsize cars, such as the Fairlane, have a rearend that is about the right width, and would be a good candidate...if you can find one. The Maverick/Granada is very narrow, about 56.5", and would not fit anything but a very early truck, or perhaps a tubbed Pro Street truck. The 60s full size Ford car rearends are usually too wide, but if you find one, measure it and see! Most earlier full size, and all mid size, cars use the 4.5" bolt pattern, while later full size cars use the 5" pattern. The Ford trucks have a big 5 on 5.5" pattern, with a big center that takes some work to redrill to anything Chevy. Ratios range from 2.47 to 4.30, and the axles come in 28 or 31 spline varieties. There is lots of interchange possible with the 9" rearend, which is why it's so popular...I have one in my 55 Belair, and in my 57 Suburban chassis. Unfortunately, they are getting expensive, especially when you have to shop around for just the right one that will fit. So...if you don't know if a rearend will fit, or what it came from, get out your tape measure and see for yourself! The most important things are overall width, and wheel bolt pattern...then concern yourself with ratio. I like a 2.75-3.0 ratio for a V-8 powered truck that will spend lots of time on the highway; about 3.2-3.7 for a 6 cylinder or small V-8 for in town and limited highway use, and the stock 3.9-4.56 ratio is great if you have to use your truck to haul lotsa weight, and you don't have much engine...just don't plan on going much faster than 55!