The Stovebolt Site Forums The Shop Area The HiPo Shop Dana 70HD or GM 14-bolt FF

I have two rear axles and need to choose one to use under my '54 GMC 1-ton. I plan to run a 454 and Turbo 400 in this truck, and will use it to pull my car trailer often with a truck sitting on it. Both are full float and both have big drum brakes.

Assuming other things are all equal, is there a good reason to choose one of these over the other?

Price the parts, gears, bearings, drums, brake shoes seals....
Then decide which one you want to buy parts for later.

I would tend to think the GM 14 bolt, as it is easier for most folks to work on, to remove and replace gears mostly. Also I think you will find that gears and locker are reasonably cheap.
They say it is a strong axle, as strong or possibly stronger than a Dana 70.

A Dana 70HD uses the same ring and pinion as a normal 70. It uses larger carrier bearings (and a different carrier). The axle tubes, (4" OD) spindles, and hubs are supposed to be Dana 80 size. So a 70HD is essentially a 70 center with 80 outers.

That said, I have a Dana 70HD, and like it, and not so sure I would want the 14 bolt (but not sure why not either). My Dana has disc brakes which I like. I already have a new 3.54 gear set waiting to go in it, but the hold up is the new carrier price. I have to have a different one to make the jump to any gear set faster than the current 4.56. A normal open differential can be found new on ebay for a reasonable price, or used for a better price. But the ARB locking differential I want (of the only two choices for a 70HD) is around $800, more than I have spent on the entire axle and all parts combined thus far. In the end I'll have to buy one, but getting it more complete and legal will come first, while I continue to search for a good deal on a new or used one.

Grigg

I have never had a Dana 70 that gave me problems, however I can pull a 14 bolt GM apart to swap carriers in a short order....

My vote would be Dana

Scott

Scott does that mean you've had to fix broken 14-bolt rears? Or just that you've changed gears in them a few times?

I vote for the GM 14 bolt. I used to maintain fleet trucks & have had both. The GM is easy to work on & the average shop can get them right. They are very strong & practicaly the only time they go bad is when they grease is not changed occasionally. If the vent tube is not positioned right water gets in & can cause premature wear. The Dana is stout but is hard to work on.

dana 70 are stout the best place that ive found them is govliquidation.com therein the m1028 and other cucvs which are mid 80's chevrolet trucks but avoid the blazers unless you want the d44 and 6 lug front and rear all cucvs are 4x4

The 14-bolt has 3.42 gears and the 70HD has 4.10 gears. The 14-bolt is 67 inches WMS to WMS and the 70HD is 73 inches. So my choices are 4 inches wider than stock, or 10 inches wider.

I was told the Dana was from a mid-80's GM Diesel pickup, though I've not looked up the BOM number from it. From the width I assume it was a dually pickup.

The 14-bolt came to me under a '50 Chevy 1-ton and I don't yet know any more about it than that.

While I'm inclined to use the 14-bolt based on gears and width, my next step is to open them up and look at condition.

I appreciate the responses. You've left me convinced the gears and width and condition are probably the important issues, the difference in maker doesn't seem to make a big difference.

Thanks!

Steve, my experience with the 14 bolt has been spider gears on the 10.5" and various Gov-Loc issues on the 9.5 semi-floats. In either case, the broken pieces are not helpful, especially for the ring and pinion.

However based on your width issue, it sounds like you may be headed 14 bolt. I would recommend that if you have the Gov-Loc, keep the fluid changed often to prevent the fly-weights from gumming up.

Scott

Thanks Scott! I do have a Gov-Loc in a 9.5 semi-float in my modern pickup. I'll be changing the fluid in it soon...

When I open up the 10.5 before mounting it under my truck, I'll check the spider gears in addition to the ring and pinion and bearings.

And I'll change the fuild in it too, but I assume that's a given if you are opening it up.

Scott I believe that Steve is referring to the older 14 bolt that drops out the front like a nine inch F@rd and they are pre Gov-Loc the later Chevy 14 bolt is almost identical to a Dana 60 in fact many truck through the 70s and 80s could have come with either

Grant my '91 K2500 has a 14-bolt semi-float with G80 with I assume is the Gov-Loc and I believe is a 9.5 inch. That's the truck you saw in Graham and is basically a driver/trailer puller. Its 17 years old, but being post '72 its not Stovebolt discussion material and I call it a modern truck.

My '89 K3500 has a Dana 70-HD with no Gov-Loc or similar ability. Until it was wrecked last year it pulled my trailer and did a much better job than the 2500.

Those two rears are not what this thread is about.

My 14-bolt full-floater I assume is 10.5 and no Gov-Loc near as I can tell. It came to me under a '50 1-ton Chevy, but is definitely not the original rear from that truck.

Then I have the Dana 70-HD I was considering for this project. I still haven't looked up the BOM number to figure what it came from... I picked it up out of a guy's yard. He said it was from a 70's or 80's GM Diesel Dually.

I also have a late 70's P30 under a motorhome and I haven't crawled under it to determine whether its a Dana or a 14-bolt. I probably should.