I"m changing my 2500 to a 3500. Didn't really think the 80 was that much bigger till the old was out and gone. I had been planning this for a while, and listed my 2500 axle for sale on craigslist, planning on not swapping them till the 70 sold. Also so a potential buyer could see it still attached to the truck and running, so proof it was good. I didn't think the 80 would be any longer from the input yoke to the centerline of the axle( Yes, I am a bonehead for not checking this earlier)Once I realized my springs were the same, I breathed a big sigh of relief.. Sooo, tonight after work, I get my new u bolts and get the axle bolted in, and now wondering if my driveshaft needs to be shortened a little. I could get a prybar and pop it in, but seems a tad tight. Anyone else done this swap and know if the driveshaft needs to be chopped?? Trying to find out asap so I can take it out, get it to the shop, chopped and back for this weekend......
If it's long, it's not by that much......

 

Yes it needs to be shortened and I think the U-joints on the eighty are larger?

 

Any idea how much shorter? It does fit, due to the sliding shaft but does seem tight. Seems to be the right u joint size. My truck has the higher gvwr..

 

Put the slip yoke into the transfer case, push it in all the way, then pull it out an inch. Now measure from the center of the u-joint caps on each yoke, give that measurement to the driveshaft shop.

 

Do what Tate says. I bet you'll find that you'll need about an inch shorter drive shaft.

 

Don't mean to hi-jack but maybe some other guys will have this same question. My 2500 has a Dana 60 rear because it was a gasser. Will a 70 just bolt right in for replacement. Also will the 60 last long with the diesel torque? Thanks

 

You definitely need an inch to an inch and a half travel on the sip tube. A shop can shorten it in an hour or so. Cost minimal if you need no yokes or joints. I had a whole shaft made when i put in a gear vendors for 200 bucks. Yokes and all. Brapp, the 60 is on the light side for the deisel, depends on how you drive it though.

 

The dana 60 is very strong , but not large enough to handle the intended towing capacity that the 70 and 80 can do. If its gonna tow , i would look for a 70.

 

No towing but I will be turning the motor up to around 300-350hp and running 35" tires with some offroading. Think it will hold up? If so ill be looking for a p-lok for it

 

My measurement indicated it was about an inch and a quarter too long. Have a friend with
The same truck I'm trying to build and had him measure, wich backed up my conclusion. Took it to the shop on fridayto have it shortened and the guy doing the work had to be taken to the er with chest pain. Soooooo, no way I'll have it back on the road tomorrow, have to wait till monday. This has actually been pretty easy. Springs were the same, as is the drive shaft u joint size. Going to hook the brakes back up tomorrow, install the fenders and then wait for monday...
I sold my 70 to a guy that had a60, hadn't heard anything back from him that it wouldn't work, but I think that truck has the more narrow springs and maybe the smaller u joints.