Diff question

[Exekiel69]

Is it possible to turn the diff gear ratio (I have 4.10 now on My 93) to a higher gear like the next highest 3.55 or even higher with out removing the entire assembly? I've never done this but I'm starting to dig some info for a possible next project of mine.

What are the options and what is the best way to do it?

Thank You.

 

[NCheek]

By entire assembly, do you mean the entire rear axle? If so then, no yiu can swap the ring and pinion in the truck.

I take it you want to take full advantage of your potential mid-size truck tranny, and you won't need the 4.10's for any deeper reduction...

 

[Exekiel69]

Yes, I'm still doing some research but I plan to install a medium duty tranny on My 93 that has a much deeper 1st gear so I thought about putting a higher gear at the rear axle to take some advantage from that and lower the rpms in OD yet the first gear will be plenty low enough.

Where can I get this from?

Thank You

 

[NCheek]

did you retain the stock ford axle in your truck, or did you go to the dodge axle? I think both the Sterling 10.25" in the ford and the Dana 70 in the dodge could be equipped with 3.08's and 3.07's, respectively.

Availability on these numerically lower gearsets may be difficult, because I think i remember saying something to the effect that Randy's R&P didn't sell anything lower than a 3.73 for the sterling...

I'll see what I can dig up

 

[Exekiel69]

I still have the ford rear end (4.10), the reason I want to change to a higher gear is bc the tranny will be replaced at the same time by a medium duty tranny. I know it will cost but the tranny will outlast anything.
What is the final ratio with the 3.08? I bet is a lot better than the 4.10.
Thank You.

 

[NCheek]

To find the final drive ratio, just multiply the Transmission gear ratio by the rear end ratio.

Getrag OD = .77 x R&P 4.11 gives a final drive of 3.1647:1
With the 3.08, you get .77 x 3.08 resulting in a final drive of 2.3716.

Depending on your new transmission, your OD ratio may be different, but needless to say, with 3.08's and OD, your truck will have some long legs... With the getrag and 3.08's you're looking at 1400 RPM @55mph, and 1800 @ 70mph. Ought to keep the ***-a-part chuggin nice and slow!

 

[fields_mj]

I'm considering the same thing on a 93 non turbo 4x4 to increase my fuel mileage. Where's a good place to get the parts, and what kind of over all cost am I looking at? I have OEM tires on the truck. Any suggestions on what the optimum RPM would be for running an F250 4x4 ext cab down the road empty?

Not trying to hijack the thread. Just trying to get info on the same subject.

Thanks,
Mark

 

[Exekiel69]

Well what I gathered so far is that You can get this tranny from big truck yards which can also lower the cost, some times You can buy a hole truck cheaper than one of this transmissions alone. In My case I'll try to stay at around 1500rpm at 65-70mph, that would be ideal for Me and the cummins.

 

[PackRat]

Bear in mind, that most axles have at least 2 carriers, based on gear range. You might need a whole carrier to go from 4.10 to 3.08. Don't know for sure, just thought it was worth mentioning.

 

[Exekiel69]

Ok back to the first question, how do I do it?
Thank to some good advice from a member (thank You Calvin, You are a wealth of experience) I will change the diff ratio first to help the engine work at the right rpm inside the power band.

Anyone have any advice as to how to go about this, meaning what goes out what goes in and how? Also I'd like to order parts locally if possible but a good reference for the parts would be good too. This is where I will ask for the parts.

Thank You.

 

[Exekiel69]

Well they quoted Me about $500 fir the 3.55 and a reseal/rebuild kit for the rest of the pumpkin He said when ever changing gears I have to replace a bunch of other parts like the yoke seal a trust washer and some other stuff included in the rebuild kit. Is this a good price? Parts are Yukon for the gear and the bearing and other stuff is timken.