I bought a book from Randy's Ring and Pinion to learn how to change gearing and other things inside the differential and axles. I could not figure out what rear and front axles I had. So after a call and some numbers on the Diff tag I gave a guy at Randy's R and P, we came to the conclusion that I had a Dana 44 front TTB axle and a Dana 70 in the rear. My 1984 did not come with a Dana 70. He also said I have 3.54 gearing and I was under the impression that I have 4.10s.

I am really excited about having a really strong differential and axle in the back


My question is now how do I figure out my gearing?

Adam

 

I don't think the Dana 70 is any better than a 10.5" Sterling. I've always read they are about equal on average. It's hard to compare axles like this though because they are both really heavy-duty and what's IN them can make all the difference. Spline count, axle size etc.
For some reason D70s are more common in duallys though so maybe there is something to the D70 I don't know about.
I have a 70 in my Cummins-Dodge and it's been flawless.
Are you sure your frontend isn't a Dana 50 TTB? I don't know much about TTB but I thought the 3/4 and 1-ton diesels had the 50 if they were TTB.

Maybe someone has done some swapping in the truck's 24-25 year life span.

 

There is a certain year range that fords 150 and 250 all had TTB front axles. From the numbers I gave the man off from the tag he said it was the dana 44 and not the 50. My truck is bottom of the line and the 50 was an option, so I am guessing the original owner didn't think it was worth it.

The weird thing about it is that I am the second owner of the truck and the guy before me to my knowledge never even touched it. Could they have just stuck it in their because they ran out of Dana 60's and didn't think the customer would be happy with a downgrade so they upgraded. 84-85 was the switch from Dana 60's to sterling 10.25 rearends.

Adam

 

The F-350s had TTB back then too. They must have switched "up" to the TTB D50 on the diesels sometime later. I'm sure the guy knows what it is by the #s.
That rear 70 thing is wierd but you can't ever say for certain what they put in trucks for drivetrain.
The 70 is a good upgrade from a 60 though. Front 60s are quite a bit better than rear 60s and 70s are a lot bigger/better than rear 60s, so you are lucky to have it.

 

Adam,

If the book you bought is Differentials Identification, Restoration & Repair by Jim Allen & Randy Lyman, page 3 will show you how to figure out your axle ratios.

Ken

 

FWIW, my '84 3/4 ton came stock with a dana 70 rear.

 

OK thanks Ken, it looks like I am going to have to pull the diff cover off and look for a stamped gear ratio on the ring gear or get some numbers off of it and give it to the guy so he can tell me if its factory or aftermarket. If it is aftermarket then I would venture to say it is 4.10's rather than 3.54's which is what the tags say came in it.

Buck20, I am thinking that my was put in from the factory and for reasons I do not know why because I have never read in the book ken mentioned or heard of Ford installing a Dana 70 on our trucks

Adam

 

How fast will it run?
3.55's will get you to about 85 MPH.
4.10's will get you to about 75 MPH.

 

how fast will a 5.13 rear get you with a zf5?

 

3300 RPM with a ZF 5 and 5.13 gears should run 78 MPH on 235/85-16 tires.

 

you can go to the dana web site and go thru thier library and find info on your axle and how to use the bom# to identify what axles and what gears are suppose to be there. the also have manuals for specific axles for repair and rebuilding.there's a drop down menu go to expert site then go to literature and catalogs and there's the manuals good luck.



www.dana.com