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First post...question on axle ratios

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Old Oct 29, 2004 | 08:55 PM
  #1  
canadaler's Avatar
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Question First post...question on axle ratios

I'm in the market for a used cube van which will see 99% of it's useage on interstate highway. My preference is for years with a 7.3IDI in it (pre '94 I believe.)

When I'm looking at vehicles, how do I tell what ratio the rear end is? I'd obviously prefer the 3:55, are there any markings, or different look to a rear end with a 3:73, or 4:10? Failing that, I guess the only other way to do it would be to drive it and check RPM against MPH (KPH in my case) and calculate it.

Thanks in advance, this will be my first diesel purchase and the info I've found on this site has been a great help so far. I doubt this will be my last question!
 
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Old Oct 30, 2004 | 12:20 AM
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Most axles will have a tag on them with the ratio on it as long as someone hasn't left it off after a fluid change.
 
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Old Oct 30, 2004 | 12:33 AM
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that number is hard to see. you will not see the 3. or the 4. but you will see a 55 or a 10 you may even get as lucky to see a .10-etc if it says there is a 3.73 gear ratio also "uncommon" i think it is the to first number, half of it is covered by the bolt. but a 3.55 will run 2200 at 70 mph a 3.73 will run 2400 at 70 mph and a 4.10 will run 2750 at 70 mph my truck gets like 12 with a heavy foot and 4.10's i'm impressed
 
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Old Oct 30, 2004 | 06:42 AM
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my 7.3 turns 2200 at 68 miles with 4.10 rear ,truck is stock for now its a4x4 ext.cab.gets about 20 mpg.readyto improve air flow exhaust and intake no trrbo on this 250,000 mile mill 1qrt oil every1000 miles.installing new injectors reman.pump .body complete rebuild ,4in.lift 315-75-16 tires =about 34in but only10.5 inches wide,insteadof12.5 betterinsnow irun my own shop and manufacture fibreglass box sides for most trucks signing off deisel weasel
 
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Old Oct 30, 2004 | 06:47 AM
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by the way i realy enjoy your site ,spend alot of time on it
 
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Old Oct 30, 2004 | 08:22 AM
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hate to break it to you, but your truck has 3.55's, unless you got a gear vendors overdrive. 70 at 2200 is definately 3.55's eople will tell people that a truck has 4.10's just to sell the truck. i have had many-a people tell me their trucks had 4.10's or 4.10 posi. if i drive the truck, i know it aint no 4.10, it is pretty rare to find one with 4.10's and if you drive one, you will KNOW its a 4.10, 3.55's in 4th gear runs like a 4.10 in 5th. does your truck turn 2700 in 4th gear at 70?? i bet it does
 
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Old Oct 30, 2004 | 08:43 AM
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Look for the axle code inside the driver's door frame and then do a Google search for Ford axle codes.

Ed
 
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Old Oct 30, 2004 | 09:12 AM
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OK, thanks for the info.

I'll look for tags and codes, but I assume from these threads that finding a cube van without a 3.55 would be a rare thing.
 
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Old Oct 30, 2004 | 10:11 AM
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89Ford I hate to break it to you ....but a ZF5 with 4.10's and 34" tires will run 71.4 MPH at 2200.

Everyone says my truck does this.
But in the post they forget to put in critical information like it is a ZF 5 or A4OD or T 19 or tire size or something else.
 
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Old Oct 30, 2004 | 11:03 AM
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sorry i forgot to state that my truck is 92 f250 4x4 ext cab e40d tranny .i am just removing the soupbowl from the breather .I was thinking of hooking the breather up to my hood scoop ,do you think this would help with air flow ?or just another make work project
 
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Old Oct 31, 2004 | 03:03 PM
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I was looking at mine, 1989 4wd 7,3

Trans K
Axle C5

It does 2500rpm at 50mph??
could this be right
 
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Old Oct 31, 2004 | 03:24 PM
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axle code c5=4.10 limited slip.
 
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Old Oct 31, 2004 | 08:58 PM
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i'm glad everyone is talking axel ratio's. i have a 91 model F-350 superduty with a 7.3 (non turbo) engine. it has a 5 speed manual o/d transmission. at 2200 rpm, i'm doing 50 mph in fifth gear. this truck is so slow that can get out and walk along beside it in 1st gear. i need to do 68- 70 mph at 2200 rpm. will i have any power at that speed for pulling a trailer. is it reasonably easy to change an axel ratio.
thanks
 
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Old Oct 31, 2004 | 09:07 PM
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snubber, your truck is worse than mine. 50 mph at 2500rpm is horrible.
 
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Old Oct 31, 2004 | 10:10 PM
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harleyjohn45, you must have 5.13 gears if you are running 235-85-16 tires

Snubber what tranny and tire diameter are you running?
 
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