Trying to figure out this 3 1/2 inch and 4 inch axle stuff out. What is the difference and how do you know which one is which.

 

Are you inquiring about the 11.5" AAM rear on your '07 with the 4" axle tubes?

 

I guess so. I was looking at lifts and it asks if the axles are 4 inch or 3 1/2 inch.

 

Were the lifts for 2nd Gens?

Dana 70 & 80 tubes are a half-inch different...

 

2006-2007 2500 and 3500

 

If I remember correctly, the 10.5" (hemi) rear axle has a 3 7/8" tube and the 11.5" (cummins) has a 4 1/8" axle tube. When I get to work I will look again.

 

I think they are asking you whether your truck has a Hemi or Cummins. I have never heard anyone ask about axle tube diameter when spec'ing a lift, but I can understand why. The hemi srw's have 10.5 rear axles. The Cummins has an 11.5" rear axle (4" axle tube).

 

i have a cummins, it says it in my signature

 

I know you have the Cummins...it says so in your signature. .

My point was that most lift kits for our trucks are sold based on whether you have a diesel or gas motor. The springs on the front are different to handle the weight variation and the rear lift is based on which axle you have for U bolts, lift blocks, etc.

Most 4WD stores will just ask you "Diesel or Gas?", not "3.5" or 4"?.

Your best bet is to go to the website of the lift manufacturer you are interested in. Their sites are pretty detailed and you will be able to get the part #'s you need so that you can verify that the retailer you are working with is getting you the right stuff.

 

Thanks now I got it. I must of got up way to early today. Thanks again.

 

when I ordered my BDS kit they asked what engine and what axle tube size
Just measure between the u-bolts is an easy way. My 06 was 4"