92 3500 or 90 350

[Dmace]

Axle Codes
43 = 4.30 non-limited slip
48 = 4.88 non-limited slip
4L = 4.30 limited slip
8L = 4.88 limited slip

I bet you have the 4.88 which is why the rpms are so high. Easy change over for 2wd vehicles but 4x4's require changing gears in front diff too.

 

[dgl24087]

The following lists the gear ratios on rear axles for 1999 model year Superdutys.

31 3.73 non-limited slip, F-250/Excursion
32 4.10 non-limited slip, F-250
41 3.73 non-limited slip, F-350
61 3.73 non-limited slip, F-350
73 4.30 non-limited slip, F-450
75 5.38 non-limited slip, F-450
78 4.88 non-limited slip, F-450
81 3.73 non-limited slip, F-350
88 4.88 non-limited slip, F-350
95 5.38 non-limited slip, F-550
98 4.88 non-limited slip, F-550
C1 3.73 limited slip, F-250/Excursion
C2 4.10 limited slip, F-250/Excursion
C3 4.30 limited slip, F-250/Excursion
D1 3.73 limited slip, F-350
D2 4.10 limited slip, F-350
D3 4.30 limited slip, F-350
E2 4.10 limited slip, F-350
E3 4.30 limited slip, F-350
EW 4.10 limited slip, F-350 (ambulance package)
F1 3.73 limited slip, F-350
F2 4.10 limited slip, F-350
F6 4.56 limited slip, F-350
G3 4.30 limited slip, F-450
G5 5.38 limited slip, F-450
G8 4.88 limited slip, F-450
GW 4.88 non-limited slip, F-450 (wide frame)
K5 5.38 limited slip, F-550
K8 4.88 limited slip, F-550
KW 4.88 non-limited slip, F-550 (wide frame)

 

[Soundguy]

There should be a metal tag attached to one of the bolts on the differential pumpkin that has the axle ratio info. Like the tag you find on carburetors.

you know.. I think I did see a tag on a diffy bolt when i was under there looking at the wireing.

the diffy cover strikes me as having been changed.. looks 'different' has a different patina on the metal then the rest of the diffy.

will look at the door code and crawl under to see what the tag says..

so.. in all of this.. what gets changed? axles? pinion and ring gear? or?

ballpark cost estimate?

soundguy

 

[Soundguy]

forgot to say.. she's a 2wd.

and thanks for the help.

this is the largest truck I've owned.. I'm on a steep learning curve for a 'real' truck to use to pull a trailer and tractor..

keep the help coming..

Right now just trying to keep her from bleeding my wallet too dry...

soundguy

 

[flusher]

you know.. I think I did see a tag on a diffy bolt when i was under there looking at the wireing.

the diffy cover strikes me as having been changed.. looks 'different' has a different patina on the metal then the rest of the diffy.

will look at the door code and crawl under to see what the tag says..

so.. in all of this.. what gets changed? axles? pinion and ring gear? or?

ballpark cost estimate?

soundguy

Last summer I had a rear axle bearing on my 01 F150 fail completely with debris getting into the differential. Had the dealer's service dept replace everything except one of the axle shafts which was OK. Cost: $1600 parts and labor. IIRC the ring gear was about $500.

 

[Soundguy]

ok.. just climbed under when i got home from work.

tag on diffy has a 39 and then 4.88

tag on door says G8

guess I got 4.88

I'm gonna talk to my mechanic tomorrow.

does anybody have any recomendations of what gear set i should go to?

Would maybee be nice to use the tow/haul mode.. but that kicks the rpm up even higher.. ..

open to sugestions.

you guys know what I do.. I pull a trailer and occasionally drive out of state to grab a tractor.. etc. like to drive in state and hit shows... etc..

soundguy

 

[Diamondpilot]

I would personally leave it alone. You bought the truck to pull. If you wanted good mpg you would have bought a Honda Civic.

Not being a smart *****

You have the bases covered.

Light towing use that Dodge Ram 1500 you have.

Medium towing use the Ford F-250 Diesel

Heavy towing use the F-450 Diesel

That is what I do. I have a Nissan Titan, F-250 Diesel, and a F-350 Diesel.

Chris

 

[Soundguy]

the mpg isn't a concern.. I expect to burn fuel and alot of it, pulling thousands of pounds down the higway..

my only concern is the speed / rpm issue.

hate to think that I am tached out to do 75mph..( ie.. 3000 rpm for 75mph ) and don't want to hurt the engine to do so.. considering at 3400, the tach marks become red..

soundguy

 

[Diamondpilot]

the mpg isn't a concern.. I expect to burn fuel and alot of it, pulling thousands of pounds down the higway..

my only concern is the speed / rpm issue.

hate to think that I am tached out to do 75mph..( ie.. 3000 rpm for 75mph ) and don't want to hurt the engine to do so.. considering at 3400, the tach marks become red..

soundguy

I can see your concern but think of how much diesel equipment runs at near peak rpm day in and out. Generators, pumps, heavy equipment, ect. I would check with some others running trucks like your F-450 but it was designed and built that way so I would not see a issue.

Just as a side note to change the gearing will require a not only changing the ring and pinion but also the speedometer drive gear and perhaps a re-flash of the computer.

Chris

 

[JESSE1]

The button on the end of the gearshift lever locks out overdrive on your truck. Tow/haul mode didn't come along until the 5 speed TorqueShift trans came out in '04. So if you lock out overdrive you're really going to be screaming.

In early '08, Ford offered both the 4.88 and 4.33 axle ratios in the F-450 pickup. The 4.88 came in the Heavy Towing package, 33,000# GCWR. Late in the year they stopped offering the 4.88 and the 4.30 was the only ratio available. They upped the GCWR to 33,000# with the 4.30. Most people who got the 4.88 don't like them for the same reasons, high engine rpm's and very high fuel consumption. The 4.30 lowers the rpm's to a tolerable level without reducing your towing capacity. I think you're going to like the truck much better if you go ahead and change out the gearing for something lower like a 4.30.

On a side note, we bought a new F-Superduty (F-450) chassis cab in '88. A 5.13 axle ratio was the only ratio available with the 7.3 diesel (before the Powerstroke). 70 mph was about the max speed, but you needed that ratio to pull a heavy load with the power output of that engine. You could get a 4.88 or 5.13 ratio with a 460 gas engine.