Why the different axles lengths?

[TX72K5]

I am sure this has been asked and answered more than once on here, but I haven't seen it in the recent posts. I think I know the answer, but I'll ask anyways.

Why is the front axle longer than the rear axle on the 4x4's? Also, what would be the correct spacing on the rear to make them look even?

Thanks, Mike

[krue]

What year you got? I know the 70 1/2 up 2wd (which should be the same as the 4wd) rear ends are 1.5 inches wider than the earlier ones. Why? I don't know.

[jhow66]

Originally Posted by TexasWreck

I am sure this has been asked and answered more than once on here, but I haven't seen it in the recent posts. I think I know the answer, but I'll ask anyways.

Why is the front axle longer than the rear axle on the 4x4's? Also, what would be the correct spacing on the rear to make them look even?

Thanks, Mike

Front axle is a Dana-rear a GM 12 bolt--you need 1 1/2" spacer for each side to make the rear track the same as the front track. My son (orangeuavol) did this on his blazer. He found a new set on ebay for $80 (6-lug). Be sure and use the same wheels all the way around for even track. No need to change studs as the spacers have them and the holes to bolt to studs on axles.

[badpeanut]

The wider front than rear axle width continued on into the '73-up trucks. I'm also interested in the reason why...

[69TowRig]

I think one of the reasons why I generally like the look of Dodge and import trucks is because the front and rear track widths are the same or nearly so. GM and Ford both had different widths.

I really want to make mine wider in the rear, I don't like the "tucked in" look. Good tip on the 1.5" adapters. Anyone have any experience with how long the axle bearings last with those?

[TX72K5]

I have a 1972 Blazer. I was told in the past they made them different lengths, so they would track different in mud, snow and so on for better traction. Of course, I dont know if that is the real reason. Thanks for the spacer info. Mike

[vtblazer]

Originally Posted by TexasWreck

I have a 1972 Blazer. I was told in the past they made them different lengths, so they would track different in mud, snow and so on for better traction.

Same as what I had heard.

Any other "reasons" ??

[Chris_T]

I've heard it was to improve turning radius .. no idea if this is true

[2wdBlazer]

I have a 14 Bolt FF rear and mine tracks Even.

[69TowRig]

Originally Posted by Chris_T

I've heard it was to improve turning radius .. no idea if this is true

That would have no effect. The wheelbase and the angle that the wheels turn in either direction are the only constraints to curb-to-curb turning radius.

[71RestoRod]

I always figured it was just to cut costs by using the same width 12-bolt as the 2WD trucks.

[Medicanman71]

Which trucks came with 12bolts and which came with 10 bolts what made the difference?

http://cgi.ebay.com/ebaymotors/GMC-C...QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/GMC-C...QQcmdZViewItem

is this the guy, are these the spacers?

[ClassicStyle]

i heard somewhere it helped them turn easier. being that the hind end was narrower then the front they didnt push so much.

-Cameron

[69TowRig]

Originally Posted by Medicanman71

Which trucks came with 12bolts and which came with 10 bolts what made the difference?

http://cgi.ebay.com/ebaymotors/GMC-C...QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/GMC-C...QQcmdZViewItem

is this the guy, are these the spacers?

Those will not fit because of the metric studs. You would need spacers with SAE studs, unless you wanted to run metric in the rear

67-72 trucks did not come with 10-bolts, those arrived during the following generation in the late 70's.

[Medicanman71]

thank you!

[mrmaxrebo]

I have a 1972 Blazer. I was told in the past they made them different lengths, so they would track different in mud, snow and so on for better traction. Of course, I dont know if that is the real reason. Thanks for the spacer info. Mike

Yep that right. The front is wider than the rear so your tires don't track in the same tracks as each other. My dad worked in a 4x4 shop when I was younger. He told me thats why they did it. As for the turning...I could see how it would allow you to turn the front wheels that much more.

[Medicanman71]

i want spacers!

[70rs/ss]

The better maybe even the "right" way to do this would be to get different offsets on your wheels. Spacers are not a great idea, especially 1 1/2". If you get 3" backspace and 41/2" backspace you end up with the same effect without the extra stress on studs and bearings. Just my thoughts.

[Tynee]

Originally Posted by 70rs/ss

The better maybe even the "right" way to do this would be to get different offsets on your wheels. Spacers are not a great idea, especially 1 1/2". If you get 3" backspace and 41/2" backspace you end up with the same effect without the extra stress on studs and bearings. Just my thoughts.

But then you have to take the tires off the rims to rotate them. Neitherthat, nor the spacers sounds like a good option to me.

How much work is it to swap one axle or the other? Can it be done in a day, if the proper donor axle is used (say, complete from drum to drum, or rotor to rotor)?

[Medicanman71]

hahaha, for get swaping axles for a few inches... that's crazy

I just need to get new rims and keep the stock/old ones.

[71RestoRod]

Originally Posted by mrmaxrebo

Yep that right. The front is wider than the rear so your tires don't track in the same tracks as each other. My dad worked in a 4x4 shop when I was younger. He told me thats why they did it. As for the turning...I could see how it would allow you to turn the front wheels that much more.

I'm also aware of the double track theory and I think it has some weight but I've also heard from knowledable old guys that this is also an old wives tale.

Originally Posted by Medicanman71

hahaha, for get swaping axles for a few inches... that's crazy

One way to swap if you want matched width without spacers is to swap with a D60 in the front and a van 8-lug 14-bolt in the rear which puts you at about 70" flange to flange. This will set you about three inches wider than a 1/2 ton D44 front.

Here's the ultimate in decadence... I didn't want to build mine up as a 3/4 or 1 ton. Too heavy for what I was after and you really need 35" or better to have any sort of clearance under a 14-bolt rear.

I too didn't want spacers or mismatched offsets... My 12-bolt was dead and I didn't think beafy enough to warrrent a rebuild.

In a moment of weakness I called Dynatrac and spec'd out this matched-width D60 rear with disks and a Powr-Loc 70% limited slip. With 16x8" rims and metric 33"s the tires fall perfectly at the edge of the wheel wells. Just the way I wanted it. I wouldn't recommend this for the faint of heart... cost me almost twice as much as I originally paid for the Blazer... Please don't flame me for building with a check book... I spent a lot of my blood and sweat on it too.

This truck handles way better than it used to... but I've got lots of mods into it so I can't say if the matched track has anything to do with it.

This pic has a pretty good angle on the rear...