Sorry about that; I had tried to set it up so that OB would copy the files to reference locally. I changed it to link directly to the original pictures...it should work now; let me know if it doesn't
bigger tires=better gas mileage?
- Thread starter bagpiperjosh
- Start date
bagpiperjosh
Full Access Member
A full-foating axle's more sturdy and can hold more weight...so, I have a feeling that either '83 and '84 didn't use the same codes after all (which would surprise me; '84 and '85 codes are identical for Dana axles), or someone swapped axles on your truck, or I'm wrong and Code 31 is a Dana 60 full-floater (the FSM doesn't specify which axle is which; only lists the manufacturer i.e. Ford or Dana, along with the weight rating). I would try to verify what gear ratio you have...I don't know from the Ford part number which axle you have; maybe someone else does? FWIW my Dana 70 has "70U" cast in the webbing near the pumpkin...I don't know if Dana 60's did similar or not...
PwrSmoke
Full Access Member
Since the Diesel was only offered only in the the F250HD trucks (8600# GVW) that only had full floaters (either a D61 to mid'85 and the Sterling after), the semi-floats offered in the regular F250 (6600# GVW) ('80-'85 it was a D60-3, from mid '85 on it was a semi-float 10.25 Sterling) (6600# GVW) wasn't part of the package. The axles are easily swapped, however, since the spring perch dimensions are the same for both axles and trucks. The input torque of the two Sterlings is the same but the GAW is obviously considerably different (5300# vs 6250 on the Danas).
Ooops, now I see he has a full floater. An '83 diesel would have had a Dana 61-1 full floater, which is very similar to a Dana 60 visually but it has some internal differences that allow it to carry gears as tall as 3.07:1. Only two ratios offered in 4x4s, 3.54 or 4.10:1. 4x2s also had a 3.07:1 but according to my '83 Data book, it was only offered with manual transmissions. I didn't look at later years.
Ooops, now I see he has a full floater. An '83 diesel would have had a Dana 61-1 full floater, which is very similar to a Dana 60 visually but it has some internal differences that allow it to carry gears as tall as 3.07:1. Only two ratios offered in 4x4s, 3.54 or 4.10:1. 4x2s also had a 3.07:1 but according to my '83 Data book, it was only offered with manual transmissions. I didn't look at later years.
With all due respect, I have seen factory light-duty F-250's with semi-floating 3.07 Dana 60's that were powered by 6.9l's. I think this option only existed in '83 and '84, and it was a very rare option, but it did exist. These axles were factory equipment, as referred from the build sticker on the doorjamb, and the trucks were factory-equipped with the IDI. FWIW one of these trucks was equipped with the only dealer-installed air conditioning system that I've seen with my own eyes...complete with York a/c compressor
Also, I know of at least two '83-'84 trucks that have factory Dana 70 axles...Mel's Moose Truck (an '83 F-250) has a Dana 70, and so does my '84 F-250.
Every early 85 and down diesel ford I have seen also had a dana 70 rear axle. I have yet to see one with anything different.
PwrSmoke
Full Access Member
As to semi-floats in diesels, or diesel in light duty F250s, I'd need to see a line ticket or a VIN breakdown to believe it. There is too much written evidence to the contrary. What you see 20 and 30 years down the road, with parts so easy to swap around, is not indicative of anything that happened on the assembly line. I'd love to be proven wrong because it would be very interesting to see one or to see evidence that they existed.
I won't argue so hard against the D70 thing because I've seen both too. The books even hint at both. I have all the Ford Data books (which are 4 inch thick books with about every detail on the trucks for a particular year) for the years we are talking about and both the F250HD and F350 (4x4 and 4x2) are listed with both D61 and D70U for '84 and '85. In '83, the book lists only the D61 for the F250HD.... which may be true for the early part of the year. Mel's truck is a later year build IIRC, so it might fit better against the '84 specs. Unless a guy watched the trucks roll off the assembly line or has seen thousands upon thousands of trucks, it's really hard to base anything on the limited samples of trucks one normally sees.
BTW, my '86 has a dealer installed AC system... which for that year was , from what I was told, the only option if you had a base or XL truck.
I won't argue so hard against the D70 thing because I've seen both too. The books even hint at both. I have all the Ford Data books (which are 4 inch thick books with about every detail on the trucks for a particular year) for the years we are talking about and both the F250HD and F350 (4x4 and 4x2) are listed with both D61 and D70U for '84 and '85. In '83, the book lists only the D61 for the F250HD.... which may be true for the early part of the year. Mel's truck is a later year build IIRC, so it might fit better against the '84 specs. Unless a guy watched the trucks roll off the assembly line or has seen thousands upon thousands of trucks, it's really hard to base anything on the limited samples of trucks one normally sees.
BTW, my '86 has a dealer installed AC system... which for that year was , from what I was told, the only option if you had a base or XL truck.
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John Deere
Registered User
I'll to check again tomorrow, but my 84 has a d60.
oregon96psd
Full Access Member
mines got a 70 also...i always thought that was the most common 
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Maverick1701
Full Access Member
it might seem that way at first but don't forget the "miles driven" according to the odo will be off which will usually mess up the MPG calculation....usually when I recalculated with the correct number of miles, my MPGs went down when I added larger tires.
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