My 52 currently has 3.92 gears. The truck tops out at about 50 mph. I'm running the stock 215 motor, 16" wheels with 6.00 bias ply tires. I may have located an NOS 3.73 ring and pinion. The parts catalog shows it to fit 48-50 and doesn't list it as available for 50-52 models. I'm assuming that all 48-52 Dana 44 rears are the same and that the new gears will fit without any issues, correct? Also, how much of a road speed improvement would I obtain by changing from 3.92 to 3.73? I know that ultimately I can change the rear out to a 9" but I'd like to keep my 52 as stock as possible.

 

Ilya, the 48-50 rears were Dana 41's, and yes, they did have 3.73's as their "usual" ratio. The ring and pinions are not interchangeable between the 41's and the 44's as far as I know and have been told. You'll be much better off just trying to find a stock Dana 41 with a 3.73 ratio and do the whole rear end swap. Find somebody who did a 9 inch swap.

As far as the drive, I can easily get up above 60 mph with my flathead 8 and 3.73 Dana 41 rear end. It can cruise near 55 mph without a whole lot of difficulty.

 

Yes, Doc, you're correct. I misread my literature. I see it now that 48-50 had Dana 41 and late 50-52 had Dana 44. I was trying to find the easiest and most cost effective solution. Looks like there may not be such a solution available. If I'm going to switch out rear ends, I may as well put in a 9".

 

What do you mean by "tops out at 50"? Is that how fast you feel comfortable taking it, based on RPM, or is that all it will go? It should be capable of going well past that on either count. Changing to a 3.73 would only make about 100 RPM difference at 55, going to a 9" with 3.50's drops it 250 RPM at 55.

 

all other things equal take 392 divided by 373 times 50 = 52.5. So instead of doing 50 you'll be doing 52.5 at the same engine rpm. At 50 mph your 215 should be turning about 2300 rpm. I'm going to guess that is near the top of the torque and power curve but no where near red line so if your are pedal to the metal at and the 215 ain't got no more then something isn't right.

 

Right now, after 50 mph, it starts to shake slightly. I know that's another issue and I need to get the front suspension rebuilt and change out the tires to the new bias ply that I purchased. I'm no where near at bottoming out the pedal at 50. The engine is rebuilt so I have no doubts that it can be pushed to go above 50. It just whines at around 50 and I know that without an OD transmission, this will continue.

I spoke with Chuck and he can get the 3.54 and 3.73 gears for the Dana 44, but I'll also need to change out to the 3.73 carrier in order to use 3.73 or 3.54 gears. I called Randy's Ring and Pinion to see what it would cost. $363 for 3.73, $302 for 3.54 and $173 for 3.73 carrier.

If I were to do the gear swap, what would be a good gear choice, 3.54 or 3.73? I'm driving on flat ground. Not many hills or mountain roads here in the city.

 

I'd vote for the 3.54 based on your conditions.

 

I second Doc's vote. I changed out the stock 4.11's to 3.54's on a 34 Tudor that I had for 15 years and it was a major improvement.

 

Here are some sites I found that may help you and others decide what rear end ratios you want/need.

Tire Sizes Chart
Engine RPM / Engine Speed Calculator