dana 44 gear change questions

[bk53]

Hi, I did the math and I think I could reduce the highway RPMs on my 53 f100
significantly by changing out the 3.92 gear. The choices I've seen are 3.73 3.5x and 3.07. I've experienced all of those gears over the years in modern cars. I think I could go from the 3500 to 2700 range at 70mph with the 3.07
The easiest parts I've found are modern. I need a different carrier ring pinion etc. It seems I've read of people having issues stuffing modern parts into old pumpkins. I know all the 9" ford ideas and all. Just wondering if anyone who has done this can share their thoughts. Its not even that I plan on driving 70 hour after hour, frankly I don't know what is a healthy cruising RPM range for a rebuilt flathead.

Thanks

Bill

[19Fordy]

3.92 is not a good cruising gear. A 3:54 or 3:78 would be much better.
Having overdrive would be a big bonus.

[scooder]

I'm interested in the modern bits into an old Dana 44 got one in the back of my '42 pickup. Mine has 4.27:1 in it which I'm keeping while I have the 51 Merc overdrive in it. But I may in the future if my knees get worse, put a C4 in it. And then I may go 3.92 or 3.73. Personally that's as high as I'd go, this is s truck and will be used/abused as a truck. 3.73 Will be perfectly fine cruising at 70. A bit more rpm than you may be used to, if you drive a late model loaf along or 45 speed New car. But it will not hurt the engine running 3.78, the 3.07 will kill it as a usable truck. And hills will be a burden.
Martin.

[Steves46]

What size rear tires are you currently running? Larger diameter tires will also reduce RPMs to a degree. Steve

[rotorwrench]

The 3.92:1 works OK with an overdrive like my 51 Merc. I was used to an old 1952 F3 my Dad had years ago. It was a 55-mph max truck with the old non-synchro 4-speed stump puller. We put a stock rack set up in it and used it to haul full grown brangus bulls and it would do that with ease.

[Ol' Ron]

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JWL's book is a good place to find this info. Torque in a stock flathead starts to fall off after 2500, but really fast after 3000. I'll have a better idea after some economy tests this summer. The Jeep Cherokee uses a spicer/Dana 44

[bk53]

Thanks fella's Yep, Martin, this is a truck as you say and the 3.07 would be car like.
Overdrive isn't an option right now because this is running a '57 fordomatic.
I need to pull out JWL's book and look for my 276, and decide I guess between the 3.54 and 3.73

I'm still; curious about new guts in an old pumpkin.

Here is the math I used, I hope that 336 is the right factor.
Gear Ratios: Fordomatic
2.40:1 1st gear
1.47:1 2nd gear
1.00:1 3rd gear
2.00:1 reverse

stock rear gear ratio 3.92

my tires are 26" tall

Rpm = mph x gear ratio x 336
--------
Tire diameter (26") in my case

60 mph = 3039 rpm w/3.92 2388 rpm w/3.08 2744 rpm w/3.54 2892 w/3.73
65 mph = 3292 rpm " 2587 " " 2973 " 3133 "
70 mph = 3546 rpm " 2786 rpm w/3.08 3202 " 3374 "

Thanks,

Bill

[Mike B]

In my '59 Chevy PU...it had 3.91's?...I think it was (posi option rear)...and a 235 6...I wanted less RPM's at speed.

Found an early GMC PU with 3.54 Dana 44.

Put it in after rebuilding it, and wished I'd went to 3.20-ish or so...235 only had about 95 HP, unsure on Torque #'s...but pulled the truck very well....Guess I'm saying 3.54's would be better than 3.73's, as I don't think you'd notce much difference.

Now if your Dana 44 was like the few I've gone through, the carrier bearings are pressed on...shims go between the inner race and the carrier...PIA pressing on/off after each patter check.

So, take your old bearings (ya going to use new ones right?) and get the die grinder out so they slip over the carrier...

I assumed that the bearings (old ones) would have .001 wear...so when contact patter was good, I'd take out .001 to each side, press in the new bearings, do a quick pattern check and be down the road.

This is assuming you are doing it by yourself, there's some neat stuff (pricey) to set them up with, but that's how I do them...

Now all that said...a 9inch is sooooo much easier

[Ross F-1]

There is only one place that has the parts needed to use a smaller carrier (<3.73) that I know of, and that is Randy's, http://www.ringpinion.com/
The problem is the coarse splines on the F-1 axle shafts, no one else has the spider gears with the coarse spline and the larger diameter where they fit into the new carrier. There is a decent write-up on using the Jeep Grand Cherokee center section with Randy's side gears on FTE.

An inch larger diameter tire would have the same effect as dropping to 3.77, worth considering. If you still have a 3-sp, I wouldn't go below 3.50 by much. I tried a 3.25 and 2nd gear around corners was intolerable.

[bk53]

Thanks Mike B, good advice. I hope to help do this and maybe learn something new. I saved your reply off. Thanks Ross, again, I have almost new tires so that's out. wish I'd considered that 3 months ago. Thanks for the link and the life experiences. I'm guessing the f-1 and f100 share the same 19 spline axles. 4
Bill

[Truckedup]

Dana 44's were used in many vehicles including some Jeeps up into the 1990's. Most later Jeeps have gear ratios from 3.07-3.55. However,I have no idea if these later model Dana carriers will fit into earlier housings. And the pinion bearings and or yoke splines might be different....Jeeps generally use a #1310 U joint