67 K20 Final Drive Ratio...
 

Sometime in the past there was a bit of a problem with my 67 K20 (250/sm420). There was some kind of failure in the rearend and the seal surface got fouled up. Whoever fixed it used a repair sleeve. They did a pretty good job but there is a constant leak on one side that makes a mess and seems to be getting worse. So today I picked up another HO52, the plan being to switch housings. I'm pretty pleased as I got the axle and an original step bumper in good shape for 100 bucks.

So anyways, the new axle has a 4.11 and the existing ratio is a 4.57. So now I have this idea rolling around in my head to maybe go to the 4.11 ratio. Should I do it? The truck is mostly my camping and hunting rig, so it sees the road a good bit. Maybe some day I will pull a not-very-big camper with it. Tires are 265/75/16s, so say 32 inches and I will never go bigger.

I compared engine RPMs at various road speeds using a gear ratio calculator on the web, and I would save a couple hundred RPMs depending on speed. I suppose this would add up over time.

On the other hand I would have to change the front ratio to match. I have set up a few gear sets before and have the tools, so I'm not worried about that. However, there seems to be several applications of the D44 through the years so I am slightly concerned about finding the right parts. Although I may be able to sniff around on the boards for a used gearset, as a quick search revealed that many think the grass is greener on the other side. What kind of interchangeability is there between front Dana 44s through the years? Since mine is a closed knuckle. How common were the 4.10 ratios in the Dana 44 equipped trucks?

I reckon I could test drive the truck with the 4.11 third member when I switch housings to see if it would be worth it, then switch back to the 4.57 third member if need be.

Also, this new axle came out of a coil spring truck, so I'm assuming things are the same other than the spring perches correct?

Re: 67 K20 Final Drive Ratio...
 

After thinking a little more, if I wanted to go with the 4.11 third member I might be further ahead to find a disk brake equipped 4.10 Dana 44.

Re: 67 K20 Final Drive Ratio...
 

You'll get a better turning radius with an open knuckle 44 too!

Re: 67 K20 Final Drive Ratio...
 

Good Luck finding a 4.10 Dana 44. Not many GM unit came that way. There were some 3/4 tons with 4.10, but by far most had 3.73 or 3.08 You can interchange any Dana 44 EXCEPT:

Ford High Pinion (HP)
Jeep HP
Anything HP
Jeep aluminum Dana 44
Late model JK Dana 44
maybe some other odd applications

Just remember that if you find a 4.10 set of gears and decide to use the entire carrier, the side gears may not be the same as what you need. Stay away from the Dana 41 (its a rear only) that looks very similar to the Dana 44

Re: 67 K20 Final Drive Ratio...
 

Are the spring perches the same width on the 73+ D44s? So if I did switch axles and went to disk brakes I would need hoses and a master cylinder, anything else?

Funny thing is I did a quick search for "Dana 44" on a local craigslist and found a 4.10 D44 and 14BFF for sale as a set for $600, but I'm not in a position to buy right now.

Re: 67 K20 Final Drive Ratio...
 

Yes, 69-87(91 Blazer/Sub) all have the same spring width in the front. If you find a 3/4 ton rear that is 73+, you'll need to move the spring perches. 1 Tons are the same as 67-72

Re: 67 K20 Final Drive Ratio...
 

Good info thanks.

Since I have 2 HO52s I probably wouldn't switch to a later axle. If I had to buy I set I'd probably turn around and sell the later rear axle. How does the D44 compare to a 10 bolt strength wise?

How late did the D44 come in the 73+ trucks?

Re: 67 K20 Final Drive Ratio...
 

Keep the HO52. They're actually very good. Check out the link:
http://www.pirate4x4.com/forum/showt...highlight=ho52

I can't remember the exact year that the Dana 44 was changed to the GM 10 Bolt. Maybe 76ish?

They definitely look different.
http://coloradok5.com/axleguide.shtml

Strength between the two is similar. Some say the 44 is better. If I recall correctly, later dana 44s have larger wheel bearings and larger axle shafts. Oh, Dana 44 housing are said to be thicker. Its been so long since I cared about Dana 44 stuff that I forgot.

For whats its worth, I never subscribed to the strength issues. There is much more aftermarket support for the Dana 44 and for that it gets my vote. A well built 44, with conservative driving can handle lower gears and big tires. I ran 4.10s and 37 for years on the rocks of the Rubicon (yes, a full size). That being said, you can blow up a Dana 44 with 33" tires if you drive it like you stole it.

A decent set of shafts and good Spicer u-joints will go a very long way. So will routine service.