rear axle narrower than front?

[cstanley]

I was noticing that my rear axle appears to be narrower than the front. do you think this is accurate?
i don't think i have a pic, and i don't know what kind of front or rear axle i have (i'll have to check when i get home.)

it's a '72 1/2t 4wd, 350/350/np205, posi out back, and i believe it to be all original. any thoughts?

if you do know it to be a little different, do you know how much? what would the backspacing need to be to make up the difference, so they look equal to the front?

[1969k10stepside]

Yes,the back is narrower than the front by a few inches.I believe the reason for the difference is because of 2 different brands on 1 vehicle.The rear axle is a GM product and the front is a DANA product.But,shouldnt the front be atleast a tad bit wider anyway?
The rear axle should be a 12 bolt.Front should be a dana 44 open knuckle.
One member I know made the front and rear the same width on his K10 with the help of wheel spacers,IIRC.You might drop him a pm.
Here is the rear axle on my 71 4x4...It's a 12 bolt.I don't have a good pic of the front.

[sick69]

yes they are different widths, although i'm not sure as to how much,

IIRC they were designed to be different track widths as to not put the rear wheel is the same ruts as the fronts, but I could be wrong it could be the different brand theory.

Frank

[Burt4x4]

It's 3" wider up front... 1.5" per side.
Why? Well I have read many reasons so who knows for sure.

[LUV2XCLR8]

Originally Posted by Burt4x4

Why? Well I have read many reasons so who knows for sure.

[jcfoote60]

They sell them on eBay. just go there and search on chevy wheel spacers, blazer wheel spacers, etc. Made of billet aluminum and bring the rear axle the same width as the front

[Zoomad75]

I'd buy the rears following different ruts over axles coming from different suppliers. Even though the axles might have been built at different suppliers, GM still spec'd what they wanted. They intended on them to be different. Keep this in mind, the 73-87 trucks and 73-91 K5's and burbs all have the same 3" narrower rear axle. Thats not a mistake. Plus once they switched over to 10bolt front axles both the front and rears were being built in the same place.

As for wheel spacers, I won't run them. Even billet, I don't want to worry if something is going to come loose and let a wheel pass me on the road. Here's a better way to get equal track widths. Go get a van axle. The 70's/80's G-vans had an axle with 3in wider track. I'm not sure about the 1/2 ton axle but I know the van 14bolt is 3"wider. All you got to do is cut the van spring mounts off and put them in the right location for a truck.

[jcfoote60]

Interesting Rob, so have you seen the spacers come loose and do what you describe? As long as you tighen everything as you would a normal rim I don't see this happening and if you are doing serious rock crawling I don't think the billets would be wise but otherwise just debating your opinion. If a guy is just doing around town or doing some hunting or fishing down some logging roads I don't think you would see an issue. wheeling seriously....that's an issue, just depends on what you do and what your willing to fab (like your van axle scenario)

[cstanley]

can it be accomplished with wheel backspacing? i.e. different wheels in back? kinda impractical to do, but just thinkin' out loud. i'm not planning on wheeling, i just thought it looked funny.

[jhow66]

Got the spacers on this one:

[Zoomad75]

You're right to a point JC, just putting around town spacers properly torqued shouldn't be an issue. I havent had a failure because I don't run them nor do I know anybody personally that has (or for that matter actually use spacers). I've heard of failures, but that alone isn't the reason I wouldn't run them. I look at it as a band-aid fix for nothing more than a cosmetic issue. Why add complexity for an extra set of studs that you should go back and recheck the torque on because they might loosen up? It's just something more to fail. Call me a worry wart if you want but I just don't want the risk over fixing the look. (one look at my K5 should show you that looks arent high on the priority scale) They might have made improvements and they don't have the problems the older ones did, but I don't see the need.

I do wheel my rig over more than just logging trails and most of that time it's done with an excessive right foot. It may not be every weekend but when it is its more than a sunday drive down a dirt road.

You can do what you want and so can I. I threw out the van axle as a better alternative to correct the look without band-aids like spacers or running wheels with different offsets. Just a suggestion, but anybody can do what they want.

[bigpig72CST]

I had also thought that putting a spacer in is harder on your bearings, b/c it pushes the rim out, which in turn puts more pressure furhter out on your spindle and axle. Just a thought, I might be crazy.

[jhow66]

Spacers go on the rear.

[Elwayno]

If you look you will find most everything cars and trucks has a wider front than rear. It is because it helps the car turn better, or sharper.

[lookingtobuy]

Just wanted to throw in my two cents, someone told me the rearend is narrower so that you know the vehicle will fit thru tight places if the front end fits, rocks, trees etc. Just somthing I heard that made sense.

[snj8198]

GM states that the narrow rears (3") are to promote a tighter turning radius, and tracking issues so the rear does not run in the front's ruts while traversing in adverse conditions.

[Green Monster]

Originally Posted by snj8198

GM states that the narrow rears (3") are to promote a tighter turning radius, and tracking issues so the rear does not run in the front's ruts while traversing in adverse conditions.

I replaced the axles on my 88 Mustang with axles from a 95 Mustang to convert to 5 lug. The axles are each 3/4" longer than the stock axles making the rear 1.5" wider then stock. It looks great IMHO, but the turning radius has suffered now that the rear track is wider than the front.

[Burt4x4]

Originally Posted by snj8198

and tracking issues so the rear does not run in the front's ruts while traversing in adverse conditions.

A buddy of mine that wheels snow ALOT would disagree, meaning that in snow you don't want to cut 4 ruts only 2...ofcoarse I myself have only wheeled in snow like twice..so this is all hear-say

[snj8198]

I would guess the pros/cons would depend on the conditions and wheeling style. Wide tire vs narrow arguements would take all day.

[Zoomad75]

I've done a lot of snow wheeling and can say the 3" narrower axle doesn't cause me any problems. Your not really cutting 4 ruts in the snow. Only the inside 1.5" of the rear tires are out of the front ruts. The rest of the rear tires are in the ruts the fronts left. Plus when turning, the rears don't follow along the same track anyway.

[1969K10]

Originally Posted by Zoomad75

I've done a lot of snow wheeling and can say the 3" narrower axle doesn't cause me any problems. Your not really cutting 4 ruts in the snow. Only the inside 1.5" of the rear tires are out of the front ruts. The rest of the rear tires are in the ruts the fronts left. Plus when turning, the rears don't follow along the same track anyway.

Yeah, but when I turn in deep snow, one of the rear wheels stays in a rut from the front & one of the rears cuts a new path. You can feel the truck twist, not turn.
But I also have heard the GM design for better traction, the turning radius improvement is new to me.
Also heard that spacing the rears out puts extra load on the bearings and seals.

[msgross]

I am putting a 12 bolt out of a 69 1/2 ton 2WD since I found a cheap posi in the JY. I noticed that it's approx 1.5" wider between the backing plates. I'll check again for an exact measurement.

PA only allows 1/4" wheel spacers on their safety inspections. i would assume that 1" spacers wouldn't be good in the long run...

Changing backspace would prevent you from ever properly rotating your tires without removing the rubber from the rims...

[Huck]

given that the rear axle widths are the same on the trucks from 67-70 and 70-72, perhaps GM widened the design of the front axle for some strange reason. I doubt it has anything to do with traction or Uncle Sam would have specified this concept on the Jeeps, 3/4 ton trucks, etc.--and they bought a lot back in them early years before HUMVEE.
I will say that my Blazer has a great tight turning radius--Can dam near make a U turn in my garage!! Wish my 02 Silverado could do that!!
Wheel spacers are cute--and effective when used carefully. If you look at the 67-72 4x4 trucks, you will see that there stock wheels fit tight on the rear axles and front hubs even before you bolt them down to the studs. THIS tight wheel to axle adds great strength to the design that spacers eliminate. 69-72 Blazers are SUPER 4x4 vehicles well know for their strength and simplicity in off road situations. I might consider wheel spacers for show, but never for go! My .02~~~Huck

[msgross]

Here's a salesmans version of this dilemma

http://www.mrtruck.net/spacer.htm

wow, never new a wider axle "SAVED LIVES" ahaha These appear to be wheel adapters not spacers. But they are adapting the same lug pattern...