OK to swap gear ratio's

[sthomps]

Just looking for some advice on swaping my rear end ratio from 3:73 to 3:55? I'm going to be ordering a new ring & pinion, rebuild kit shortly but I was thinking that swaping the ratio might help a little with the mpg I'm getting. The other thing I haven't found to much info on is the whether or not this sawp will affect my pcm. From what I read the VSS is using the tone ring in the diff, so from that I'm thinking that the gear swap shouldn't effect the PCM? Is this correct? The truck is 2wd, auto and I only tow a car trailer maybe 3% of the time. Thanks.

[WD40]

If you are going to drive this same truck for the next 200.000 miles then it might pay for the swap, but for most people they never get there money back form fuel saved.

Doug

[sthomps]

The rear end needs rebuit anyway. The pinion was loose enough that it was rubbing the carrier.

[WD40]

Then you have no chose but to rebuild it, so I would say go ahead. Wish you could use these 3.08s I have in my shop. LOL

Doug

[sthomps]

Anyone else that's swaped ratios?

[sthomps]

Bump......

[m-chan68]

Going from a 3.73 to a 3.55 isn't going to yield that much in the way of fuel savings, but if you need to rebuild your rear gear, it won't hurt. Just count your blessings you don't have a 4WD truck or you'd be doing TWO ring and pinions if you were to do such a swap.

[Restoman]

Advice? Let a clutch and driveshaft shop that has been doing it for 30 years handle it. Would the carrier allow you to go down another ratio?

[sthomps]

They sell a rebuild kit with the 3:55 ratio so it should fit. I think the new powerstrokes you can get 3:25 ratio so it shouldn't be an issue.