Long story short, my computer has been exhibiting the 'rear axle whine' that there's a TSB out for. Brought it into the shop, and it turns out that the ring/pinion has to be replaced.

I said "Hrm..." and the service guy says "Whatcha thinking?"

I said "Well, the ring and pinion has to be replaced, and since you're already going to do that, can you upgrade from the 3.55 to the 3.73?"

They said that while I'd have to pay for the diff. in price, they would do the upgrade for me under warranty. Joy!

My question is, what kind of difference will that show, gas-wise, torque-wise, etc.

 

The price of new 3.55 gears (Ford was going to buy them anyway) should be almost the same as the price of new 3.73 gears so check the parts price list on your bill. It should only be a few $ to upgrade. You will see about a 5% increase in rpms. After you correct the speedo and quit jumping out of every signal you should get a 1 mpg increase. The truck will accelerate better and feel more responsive cause it's not having to work so hard to turn the wheels.

 

Don't waste your money on 3.73:1 gears unless they are very close to the same price. If you can swing it I would get 4.10:1 gears.

JMC

 

I was going to say what JMC said. I really see no point in going from 3.55 to 3.73, there is such a little difference.

Only thing with 4.10's is youll be wrapped up a little more at high speeds-but it wont be a whole lot. Probably loose a little MPG, but nothing big.

 

Yeah, but there IS a difference, and the cost to me is almost nothing. As far as 4.10 goes, I guess my entire overall point is that FORD is going to do it UNDER WARRANTY....4.10's aren't a 'stock configuration' item so I would DEFINITELY have to pay for ALL of that, whereas with the 3.73's, I only have to pay for the slight (like $100) diff in price, and the part's still under warranty.

 

The point I am trying to make is that the $100.00 you would spend for the 3.73:1 gear is wasted. You will hardly notice it. Anti up for the price of the 4.10:1 gears and you will notice the difference. Ford racing does make a 4.10:1 gear. Ask them for price difference for that gear instead.

JMC

 

Here is the difference between the 3.55 and the 3.73...

(3.55)
hahahahahahahahahahahahahahahahahah
(3.73)
hahahahahahahahahahahahahahahahahaha

here is the (4.10)
hahahahahahahahahahahahahahahahahahahahaha

 

I would stick with the 3:73 unless you later plan to go with bigger tires which will efectivly put you back at 3:55

I have 4:10 and they are not great for highway but good for everthing else. I di go with larger tires (from 245/70-17 to 295/70-17) so my effective gearing is now around 3:85

It actually works much better pulling and on the highway.

only my 2 cents

David

 

You left off an "a" on the 3.55s

 

Quoting Raoul:

"Here is the difference between the 3.55 and the 3.73...

(3.55)
hahahahahahahahahahahahahahahahahah
(3.73)
hahahahahahahahahahahahahahahahahaha

here is the (4.10)
hahahahahahahahahahahahahahahahahahahahaha"
>
So besides making me lmao while reading this what is the mathmatical significance of the ha?

Well the point he is trying to make is that there is only a 5% diff or so between 3.73 and 3.55 where there would be a 15.4% or so diff between 4.10 and 3.55. Personally I say go for it. If you want to switch it will make a noticable difference but don't expect miracles.

 

That's all I'm asking for - a BIT more torque and such, and that's it. Trust me, I would LOVE to ante up for the price of 4.10:1 gears, but a) I drive enough on the highway that gas MPG will go down noticeably for me, and b) the Ford dealer won't do it unless I pray for the whole deal, considering that my model truck doesn't use 4.10:1 gears as a stock configuration.

 

I think 3.73's are a good swap on a highway driven vehicle, if you want the effect of 4.10's after that go get smaller tires.
Alan

 

I got 410's and posi last month - wish I had looked into 430"s -
I do so little highway driving that I would be o.k.

The first impression driving away from the driveline shop was
I like the posi as much as the gear set - I never break that one tire loose any more, but it is is a little chirpy at slow speeds.

The bad side is that this vintage truuck can not be re - geared or programmed for speedo or odo so

 

computer programming is not needed in a 98 f150. You simply replace the VSS gear with a different size to get your odemeter back to normal.

 

Unless they are replcing the whole axle don't get your hopes up for this fix. Iv'e had the bearings and ring and pinion replced twicw and I still have the whine. Do you know exactly what the TSB is ? Good luck