moving rear axle back 1 inch

I just currently had my Dana 20 transfer case rebuilt with Tera Low gears and a new larger 1 3/8”-32 spline rear output shaft to help strengthen the drivetrain. This output shaft is 1.5inches longer than stock and I don't want to shorten my already short CV driveshaft. I am thinking on moving the rear axle back about the same distance without moving the springs. Are there any negatives to doing this? I understand I will need to modify the fenders but I would like to keep the stock fender flares that I have. Has anyone done this modification? Did you use different flares?

 

I have done it several times by drilling another hole in the spring perch. I have seen a couple of aftermarket spring perches that were longer and already had holes drilled. Would make sure that u-bolts are good, and wouldn't run it with high horsepower but it is a quick fix.

 

Why wouldn't you run it with high horsepower? What is the potential problem?

 

do you have a rear tank? check your clearence -clarence. my diff will bearly hit the tank but I don't have a stock set up.

 

check your clearence -clarence
whats your vector -victor?

 

With just drilling another hole it doesn't have as much stability to counter axle wrap. Not ever a problem with a v-6. Or any AMC motor as HP isn't an issue with those.

 

axle wrap is not caused by HP its caused by TORQUE. And all the AMC motors have loads of that at low RPMs

 

New 401 does have a lot of torque...... about 480ft/lbs. So why does moving the rear axle back 1 inch cause a anything different?

 

I would try to make the surface area from your new hole the same distance as the old location by fabricating an extension onto the spring perch.

 

Nothing "has to be centered" Why would the axle have to be centered over the spring center bolt. That bolt only has two functions. 1. Hold the spring pack together. 2. Locate the axle. The axle doesn't know if it is one inch behind or in front of the spring bolt. Like I said in a earlier post, you can simply drill another hole in the spring perch already welded to the axle- I have done this many times to move axle to back-or purchase a longer spring perch that is made to move the axle. Several speedshops sell these, and even sell ones with adjuster bolts for circle track cars that align the rear end.-Not adviseable for off-road applications- With a longer spring perch you can offset the possibility of unwanted axle wrap. This is a very simple elementary level mod that can give you some adjustment on your driveline length.

 

I've used this type of plate before.



Using one hole gives a shift of 1/2". If you use the other, it gives a shift of 1".

 

Yes the u-bolt plate would limit you to the 1". The plates MPC put in the pic look like a good option and give more of an adjustment.

 

Daryl..... I appreciate all the feedback but you still haven't answered why you can't run much torque when doing this mod.

 

With a hole drilled closer to the edge of the spring perch you lose some of the stability of the perch. It is easier for the torque to "lift " the spring perch. As you move the twisting force away from the center of the perch it is like moving the fulcrum closer to a load. If wanting to do this with a big motor it might be a good idea to buy a spring perch that is longer and gives a little more stability. I have been able to buy longer ones to do a spring over which helped considerably with axlewrap. I saw one Jeep that had the spring mount extended about 3" to do the exact same thing. Not trying to make this seem difficult, just don't want someone to do one thing and experience unwanted side effects.

 

http://www.atozfabrication.com/store/product.php?productid=16190&cat=0&page=1

 

http://www.ruffstuffspecialties.com/catalog/ubolts-plates-c-15.html?page=2&sort=2a