Rear end ??
 

Was at u pull it today just looking at 78 gmc 1 ton dually. Getting serious about making my 1500 a dually. Wanting a corp 14 but this truck had what looked like a dana 60 but the tubes are around 3 1/2-4in. They visually look bigger than the dana 60 I have. I know dana makes a 70 and a 80. What I have found is it could quite possibly be a 70 or 70hd. Did some measuring and center to center on leafs is about 42 1/2 on mine and about 41 1/2 on the 78. Backing plate on mine is about 52 1/2 and 55 1/2 on the 78. I measured center tread on mine and the inside dually of the 78 and both are about 64 1/2. My ? Is do you think this will be a good candidate. I think the measurements are pretty close. I'll have to get a combo u joint to attach my driveshaft. Maybe manufacture break lines but other than that I think I'm good. What are your guys opinions

Re: Rear end ??
 

here is an axle application chart, it works for front and rear applications, hope this helps

Re: Rear end ??
 

What lubes are preferred or factory for sm420 4speed 2wd both rear end and tranny ?? thanks for all input JM

Re: Rear end ??
 

80-90 gear oil in axles and trans, not synthetic

Re: Rear end ??
 

Thanks ilvracn ! Nice 66 jmf

Re: Rear end ??
 

your 63 is looking good also

Re: Rear end ??
 

Thanks just keep working on him JMF