I have read through several threads on here which have answered some of my questions, but still had a few left.
I have a 91 F-superduty(450) with ZF 5spd and a dana 80 rear end. Due to my top speed being around 60 mph i'm fairly sure i have the very low ratio of 5:13 or something like that. I am badly needing to turn this truck into a vehicle that can cruise at more economical/lower rpm rate. This truck has been customized to be the ultimate long haul machine (which is what i will use it for) except for the fact it is geared so low! I do use it to tow about 1/4 of the time, the rest of the time it is hauling equipment on its flatbed without any trailer. I know these trucks are geared to haul heavy loads, but would like to change the gear ratio, and then turbo it to make up for any lag that would cause. The trailers and loads i pull with it are not that heavy or big.

My question is: What is the highest geared ratio that was available in fords dana 80? I think a 4:10 would be a good ratio, as i have that ratio in my 94 250 idi also with a ZF 5spd, and it pulls along very well and can cruise at 70mph just fine. I would like to simply change rear ends if possible, since that seems to be the cheapest option.

 

Truck can be seen in my "garage".

 

Ford Axle Code Chart .: Articles Here is a link to the axle code chart. Looks like 4.63 was the only other stock option. Also note that the Dana is rated at 11000lbs.

 

Thanks for posting that chart! Anyone know about what top speed with 4:63 gears and 5spd would be? I'm afraid not fast enough. My other truck with 4:10's is O.K at around 70mph, but 75 is a tad to high on the tach for long distance.
Is it a possibillity at all to put in an 8250 lb axle in its place? Would any other axles even bolt on instead of an D 80?
Or would other internals from a chevy 80 or dodge 80 (with higher ratio)fit in my current pumpkin?

 

3.55 GEARS ARE AVAILABLE FOR D80 !

 

Really? I would be afraid if i went to that ratio this truck would be a total gut bomb? Also afraid of the cost if i had to gut the current pumpkin and swap in gears (i've heard it gets expensive). 3.55's would definitely give me a great cruising speed however! This is a heavy truck! Not sure if it would work?

 

I say that because I have a 94 dodge 1 ton with a D80 and it has 3.55 gears in it !
now maybe you could find the whole carrier assy. from a dodge with the ratio that you like and install it !
this is assuming that the 2 would be the same ! the side gears would be the thing that i would think might be different !

 

"The trailers and loads i pull with it are not that heavy or big."

well,i hate to state the obvious......but......lol.then you probably mistakenly bought the wrong rig.
it must have been a good deal i take it?
problem with buying a larger/heavier truck than you need,is the added expense all the way around to drive,insure,and maintain it.
an empty f450 is too heavy for 3.55 gearing imho (i personally went lower gearing via shorter tires with just my f250 due to it's weight an work duties.i would not want a true 3.55 gearing with 235's on my truck i know this.the thing would be a turd.)
if i had to buy an f450,id pay to have a set of 4.30's installed and add a GV OD unit (starting with the E40D trans.) just guessing without looking it up.whatever got me to 1400ish rpms at 45 mph in double over.lower gearing if need be (guessing again,just adding a GV would work for my speeds with one of the stock ratios.) just find an online calc and enter your trans final ratio and experiment with rear axle gearing to get the rpms you want at your 75 mph speeds.im gunna guess though,it's too high of gearing for the weight of the truck without adding a GV so you can keep some performance to her.go too high on your rear axle gearing for a 9k lb empty truck and it'll just be a slug around town.put extra stress on the drive train and get horrible city/rural economy.
it's likely the only thing cheap about your f450 purchase is going to be the purchase price.adding double over,and or gear swaps to make a much more "pickup" friendly use vehicle is going to set ya back.don't do it,and you'll pay it anyway in fuel.
it's always good to have a budget plan prior to buying to find your true truck price.

 

[QUOTE=FORDF250HDXLT;11637921
an empty f450 is too heavy for 3.55 gearing imho [/QUOTE]

There's not that much of a weight difference between a DRW F350 and an F450. And many guys get by just fine with a 3.55 ratio. I would go with 4.10s for a best compromise.

Figure about 750-1000 for a gear change, depending on if you opt to have the bearings replaced in the differential.

I was thinking there was a 3.08 available, but the lowest I see is 3.31.

Jason

 

For what it's worth, I've got factory 3.55's in my 87 F250HD with stock 7.5L 460cid and T19 4 speed (haven't determined if the rear axle is a D70 or D80 yet but it's got 12"x3" brakes so probably D80), and wish I had higher (lower number like 3.08) gears. When pulling a "light trailer" - towing a car on car trailer so around 4800lbs I can't even tell the trailer is there - effortless to pull even up pretty good hills, and my RPMs are higher than I'd like at 55+ MPH. That's of course in 4th which is only 1:1 output gears. if I had a 5 speed and moderate to heavy trailer I'd be in 4th, light or no load I'd be in the higher gears and I'm guessing your rig should have more torque than my 460 with 155000 miles and counting.
Hope that helps...

 

Most likely has a 70 or a 10.25.

Jason

 

Thx Jason, is there an easy way to tell if it's a 70 (or 80 if they were around in '87) or a 10.25? I've got another thread on this very topic...

 

I believe the Dana axle had a 3:54 ratio, Sterling was 3:55. I don't remember if the axle had to be pulled to check brakes on the Dana, been too many years since I had the 84'.

 

Danas will have the fill plug in the cover, the sterling will have the fill plug in the drivers side of the housing a head and above of the axle tube.

 

OK, my axle has 3.55 gears and has the plug - "fill plug in the drivers side of the housing a head and above of the axle tube" so it appears to be a Sterling then. So I've learned from this I can't tell a Sterling from a Dana by just looking at the back of the diff under the truck...I think we're digressing from this main thread though - so let's let the thread get back to it's focus - thx again guys