I need gears asap...

[IDIBRONCO]

I just picked up an 85f250 a while back. Same problem. I'm going to swap out the 4 speed trans for a zf5. I do tow some once in a while so I still want the lower gears. Besides, I've always liked the way the zf shifts WAAAAAY better.

 

[LCAM-01XA]

you can find them stock in the semi-float version of the 10.25
light 3/4t trucks with the 302 or 351w powering the truck will have them.

Quick decoder for axle code on door tag, the first character (number or letter) signifies GAWR, the second character (digit only) shows gear ratio:

Axles (Ford only, not Dana):
3800 lbs GAWR: "1" is open differential, "H" is limited slip
5300 lbs GAWR: "2" is open differential, "B" is limited slip
6250 lbs GAWR: "3" is open differential, "C" is limited slip
7400 lbs GAWR: "4" is open differential, "D" is limited slip
8250 lbs GAWR: "6" is open differential, "F" is limited slip

Some common gears (again Ford only, not Dana):
"5" is 4.10
"7" is 3.31
"8" is 3.08
"9" is 3.55

So to quickly find a junkyard truck with the desired gears, one should pretty much just run from truck to truck and look for the code they desire. In my case I wanted 3.55 LSD, so I was looking for ideally a B9 or a C9. If that wasn't in the cards, I'd have settled for a 29, a 39, or a 49 (open differentials with 3.55 gears) and then swapped their gears over onto my own LSD. I did find a C9 tho, and stuffing it into my 7400 lbs DRW axle technically made it into a D9.

Thus if one is after a set of 3.08 gears, look for an axle code of possibly "28" or "B8". Or, to save time, just ignore the first character altogether, and instead look at the rear axle first to make sure it's a semi float, and only then open door and heroically battle swarms of bees and wasps and hornets (or in extreme cases a bear or two) for the privilege of reading the tag looking for the second character of the axle code to be an "8".

 

[The Warden]

A square fill plug doesnt mean you have a dana axle. If its on the diff cover itself, though, that indicates Dana, unless someone did a mod. My 85 came with a 10.25.

1985 was a crossover year...you could have either axle.

FWIW, to complement LCAM's list, here's a list of Dana axle codes from my '84 shop manual:

31 - Dana axle, 6250 lb capacity, 3.07
32 - Dana axle, 6250 lb capacity, 4.10
33 - Dana axle, 6250 lb capacity, 3.54
34 - Dana axle, 6250 lb capacity, 3.73

42 - Dana axle, 7400 lb capacity, 4.10
43 - Dana axle, 7400 lb capacity, 3.54

52 - Dana axle, 7400 lb capacity, 4.10
53 - Dana axle, 7400 lb capacity, 3.54

62 - Dana axle, 8200 lb capacity, 4.10
65 - Dana axle, 8200 lb capacity, 4.56

72 - Dana axle, 6300 lb capacity, 4.10
73 - Dana axle, 6300 lb capacity, 3.54

C2 - Dana limited slip axle, 6250 lb capacity, 4.10
C3 - Dana limited slip axle, 6250 lb capacity, 3.54

D2 - Dana limited slip axle, 7400 lb capacity, 4.10
D3 - Dana limited slip axle, 7400 lb capacity, 3.54

E2 - Dana limited slip axle, 7400 lb capacity, 4.10
E3 - Dana limited slip axle, 7400 lb capacity, 3.54

G2 - Dana limited slip axle, 6300 lb capacity, 4.10
G3 - Dana limited slip axle, 6300 lb capacity, 3.54

It's VERY rare on these trucks in my experience, but if your axle code is three positions (i.e. G22), it means the front axle has limited slip...but, again, I have yet to see a truck that was actually equipped this way from the factory.

Hope it helps some...

 

[LCAM-01XA]

Warden, I saw a 29N while looking for my B9/C9. If it was a 39N that entire front axle would have gone home with me that day.

 

[The Warden]

Warden, I saw a 29N while looking for my B9/C9. If it was a 39N that entire front axle would have gone home with me that day.

That was in a 250? I'm impressed! I had always kinda figured that it was more of an F-150/Bronco deal...but, again, I don't know either way...

 

[LCAM-01XA]

Yeah, pretty sure it was a D44 tho, which is of no real use to me. D50 would have been much more suitable for my needs. After converting it to coils that is.

 

[jaluhn83]

85 is the split year. Seems like somewhere 01/85 they switched to 10.25 rears and the later style 6.9 block.

I had a 3.31 dana 61 rear in my rig for a while - worked much better than the 4.10 I had before but definitely low on torque especially once I had a ZF5. Managed to burn up at least one clutch pulling trailers up my parent's driveway.

I'd suggest swapping the entire rear - much easier than messing with the gears and much easier to find a rear. AFAIK, pretty much any 80-96 full floating SRW rear should bolt in. Only issue might be the rear u-joint but they make hybrid joints to fix that problem - just measure both yokes and go to your local parts store and ask. Or just look it up in the reference book.

 

[LCAM-01XA]

ok so update...i found a number on the axle housing... it says 353b so i am guessing that it already has 3:53's in it...i hope not cause if so i need 3"08's

Look up the sticker on your driver's door jamb, find the 2-digit or letter-digit code in the "AX" slot, and post it here please. Just to make sure you do indeed have 3.54 or 3.55 gears, and it will also tell us what axle they are in.

I'd suggest swapping the entire rear - much easier than messing with the gears and much easier to find a rear. AFAIK, pretty much any 80-96 full floating SRW rear should bolt in.

True, but since only semi-float Sterlings ever came wit 3.08 gears swapping the entire axle would be a downgrade in strength. Suppose he could do a 3.31 D61 like you had tho...

 

[jaluhn83]

Wouldn't go to a semi float, but the 61 is plenty strong for just a straight light truck and even light towing.

Course the other thing to think about here it the cost benefit ratio - how many miles do you have to go to save enough fuel to be worth the cost in time/money? Got the aspect of engine rpm too, but these engines will handle high rpms all day long without problems unless there's some pre existing problem.

Or just slow down......

 

[riotwarrior]

IIRC 10.25 has smaller diameter axles and would require a ring pinion swap instead of an entire carrier swap, even there I'm not certain that this would work.

Again OP needs to really check gear ratio out by pulling diff cover or...JUST slow down a bit...10 MPH isn't going to make a huge difference.

jm2cw

 

[manimal]

I am not sure about the width difference, but I ad a D61 in a 77 f250 and it had 3.07's. I got 14mpg with a 460 in that thing. and it would just sing goin down the fwy at 70.