Dana 70

[loganstecker]

i have an 84 c30 and i wanted to figure out if i had a dana 70 or dana 60 i know the truck has 4.56 gears in it because of the rpm im turning over but i wanted to figure out which one it is and if its open diff or limited slip i dont have the rpo in the glove box but i do have all the original owners manual and service manuals specifically for my truck

 

[legopnuematic]

Cab and chassis? Single rear wheel pickup? Dually pickup?

A cab and chassis and single rear wheel C30 would have a corporate 14 bolt full float rear.

A pickup dually C30 would have a Dana 70HD rear.

 

[bucket]

Also, if calculating gear ratio based off of road speed and rpm, you must know the actual (rather than just what the manufacturer states) diameter or circumference of the tire. Also if automatic, torque converter slip needs accounted for.

 

[loganstecker]

Its a crew cab dually 3+3 and yes i accounted for all of that i know its not 4.10s its got a turbo 400 in it with 30” wheels at 60 mph im at 3,100 and at 70 im at 3,500

 

[loganstecker]

Ive also had the tires spinning once and it was just the one time which is why i wasnt sure if there was a way to tell if its open diff or if it is pozi and the clutch pads are wore out

 

[legopnuematic]

Easiest way to tell if it’s a powr lok or open is to pull the cover and see.

And if you don’t have a history on it, or haven’t done it yourself yet, the gear oil is probably ready to be changed anyways at a minimum.

 

[bucket]

Far as I know, GM never offered a posi or locker for the D70.

 

[legopnuematic]

Far as I know, GM never offered a posi or locker for the D70.

Interesting, I’m going to have to look into that for my own curiosity.

I freely admit my Dana axle knowledge is based around the Dodge applications.

 

[legopnuematic]

A quick trip over to the 1979 truck brochure does indeed show no option for a powr-loc/locker for the Dana 70 equipped trucks.

Learn something new every day.

 

[nvrenuf]

Since GM only used 70's in dual wheel applications, I imagine a posi / locking diff would be prone to breaking axles (especially under a heavy load).

 

[bucket]

Since GM only used 70's in dual wheel applications, I imagine a posi / locking diff would be prone to breaking axles (especially under a heavy load).

I always thought that maybe they didn't offer it due to tire scrub. Like possibly due to the overall track width and the locker trying to engage on every turn.

No matter the reason why, I sure wish mine had some type of locker or posi anyway, lol.

 

[nvrenuf]

I always thought that maybe they didn't offer it due to tire scrub. Like possibly due to the overall track width and the locker trying to engage on every turn.

No matter the reason why, I sure wish mine had some type of locker or posi anyway, lol.

Nothing a few hundred bucks (or more) can’t fix.