Will my speedometer still work correctly and will everthing bolt up just right from an older 94-01 dana 80 to my 2001 truck that has a dana 70 in it now. Im sure the driveshaft will need to be modified but other than that would everthing work out. Any info would be much appreciated. My 70 is broke

 

Anyone????

 

brett broke the pinion in his dana 70 over the weekend and we found a dana 80 out of a 94 dodge and we are wondering if it will work in brett's 2001??

 

I'm pretty sure that the 94 to 97 model rear axles don't have a tone ring. To check, just look on top of the housing. There should be a place to plug in an electrical connector. That plug is attached to a magnet inside the diff that reads the teeth on a tone ring inside the diff. That reports speed back to your truck. So if the replacement axle does not have that plug, then you'll either want to find another one, or do some mods.

You can either install a tone ring (I think the one from the 70 will work) or you can hook up a Dakota Digital SD2 box to your transmission VSS output and get your speedometer reading there. The box costs a couple hundred bucks I think. Look up Dakota Digital's site if that is a route you are interested in. It would require some wiring, obviously, and some fine tuning to get it dialed in just right.

The best option is to find a new axle from a 98 or newer truck, as it will have the tone ring and will be a total bolt-up. You might need a different U joint for your driveshaft but I don't think you'll need to modify the shaft itself. My Dana 70 uses a 1410; I think the 80 uses a 1410 also, but I'm not positive. You'll just have to look it up. NAPA is your friend.

 

Yeah i was thinking the same thing as you but i had the axles out of it and i drove it down the road with just front wheel drive and i still had a speed reading so it must work off the tranny, cause my ring gear wasent moving with the axles out, and i talked to someone else and they said it read off the tranny, but i know my rear has a tone ring cause i've replaced it before but i dont know what it's for it must be something to do with the way the ABS works

 

How much larger diameter is the ring gear in the Dana 80 over the 70?

 

I dont know exact but it is much stronger, as the pinion shaft is too.

 

http://kydtr.com/iboard/index.php?showtopic=12633

in kentucky...and i happen to know some local guys going to kentucky may 10th

 

Your low-speed readings are taken from the tone ring; high-speed readings are taken from other sensors. On trucks with ABS up front, that is where that reading comes from. There is no reading from the transmission. Otherwise, when you are in 4 low (or 2 low, if setup) then your speedometer would be way off. ;-) Older vehicles get a speed reading from the rear output on the transfer case, but not on newer vehicles.

The Dana 80 uses an 11 inch ring gear and the Dana 70 uses a 10.5 inch ring gear. The internals aren't all that much bigger, but the housing on the Dana 80 is gigantic. You basically get a D80 center section with D70 tubes. It's not a "true" Dana 80 but it's definitely big enough. Weight ratings remain basically the same, torque input is about the same. Going to a stock D80 is a slight upgrade in strength.

EDIT: Just make sure that the new axle has the same gears as your front, or plan to switch out one of them. Kind of a no-brainer but I thought I would throw it out there.

 

Yeah I think im gonna drop one in from a 98 with 3.54 and drum brakes

 

Thanks for the informative post.

On a 2nd gen, the D80 tubes are larger than the D70 tubes - by a half inch, IIRC.

 

Only with a dually...with a manual/SRW truck, they are the same size
Chris

 

Well, last weekend we installed traction bars on two 2nd gens w/twins for the HPP dyno event. Both were 2500s, one auto and one manual. The manual had the larger D80 tubes, while the auto had the smaller D70 tubes.

What exactly are the differences in Dana model among the 2nd gen 2500 & 3500, 47RE/48RE & NV4500/NV5600?

Be nice to know for sure so we send out the right parts the first time!

 

Lookin to go pick up a 98 dana 80 tomorrow, and my friend said to double check about the axel lengths cause he had a 96 and 2002 and said he tried switching tires around and said the new wheels on the 96 were tucked in under the truck alot and didn't look right and he tried the 96 wheels on the 2002 and said the stuck out farther, so if anyone knows for sure if the lengths are the same please let me know. So i dont get the wrong rear.
Thanks Brett

 

Brett, What did you break the R/P or the spider gears ? Thanks Steve B.