Changing differential gears

[delwhjr]

WWould like to hear from those that have actually changed their rear-end ratios.
Did you get any improvement?
Was it worth it?
Any pitfalls?

[dodge_guy]

Glad to hear it worked out! This is good info. for others that are considering the change.

[parker_rowe]

Great! I had similar results recently. Not disappointed at all.

[time2roll]

Excellent :B

[wilber1]

I went from 3:55 to 4:10 in a 2001 Dodge Cummins auto because we do a lot of towing in the mountains. I was a good move for me but the truck was a 2WD so it wasn't as expensive to change. My speedo wasn't affected because the sender was in the axle downstream from the differential on that truck. The Durango might be the same.

[delwhjr]

UPDATE

Got the new gears installed. Went with a 4.1.
Made a 2k round trip and noticed a great improvement.
Gas mileage went up about 2 mpg and it no longer went to hunting gears on small inclines.
Very happy with results

[Huntindog]

delwhjr wrote:

Huntindog wrote:
Has your buddy ever set up gears before?

Too many to count

Good.

[delwhjr]

Huntindog wrote:
Has your buddy ever set up gears before?

Too many to count

[Huntindog]

Has your buddy ever set up gears before?

[delwhjr]

Huntindog wrote:
I have a 73 Blazer that I bought in 85. It had 3.73s. That reved pretty good with stock tires and the TH350. When the tranny went, I installed a TH700R4. A lower 1st gear, and an overdrive made this a great choice. It was my first TV. Then one of the front springs broke while I was towing. Made it home fine with it that way only discovering it when backing into the drive. Priced new stock springs....Ouch.
So ended up with all new 2.5" lift springs/shocks for a lot less $$$. Then the stock tires looked silly, so at new tire time, 32"s went on. Then the OD was too steep. Mileage went down a lot and OD wasn't much use. When it was axle rebuild time, I installed 4.10s front and rear with a Trutrac in the rear and an Auburn in the front. I did it myself.
Cost wasn't bad at all. It did take some time and a few new tools.

What a difference! Mileage improved by 29%!!
power was better in every gear.

So yes, if your present gears are not working for your situation.... Getting the right ones for the job will make a world of difference, and very well may improve economy as well.

I am positive that my initial cost has been returned and then some, over the last 10 years in fuel savings. The better drivability is a bonus.

Thanks. My CAT numbers are good. I was just looking to improve shifting and short hill climb performance.

[delwhjr]

patperry2766 wrote:
What part of Texas do you live in?

A lot of the bigger towns have 4x4 shops. Might be worth checking with them. Years ago, I had a Toyota 4x4 that I went with bigger tires on. I did the work myself to remove the axles and pumpkin (wasn't really that hard), bought the parts and they put then in the pumpkin and shimmed it for about $100. Probably more now.

Company is 4 wheel parts and they have stores in DFW, Austin, San Antonio, Houston, Beaumont and McAllen. Any good axle shop should be able to easily do the work.

Live in N. Texas
Friend is helping with change out(he has garage and all the goodies to make life easier in the tools. Just looking for real life experiences to confirm if it had any validity or just garage talk.

[dodge_guy]

mtofell1 wrote:

ol' yeller wrote:
Gas mileage didn't improve or degrade enough to notice.

I think this is what a lot of people need to read and reread. Whenever gearing discussions come up, the whole MPG thing is way overstated. Unless you are doing a very drastic change it likely won't be noticed.

Just to throw some real numbers out there.
With my 3.73 to 4.30 swap I gained .5 mpg towing and the same amount in city/hwy driving. I did lose that .5 mpg on the hwy with no trailer, but when you go from 14.8 to 14.3 its not a dealer breaker! and the X very rarely doesn't have the trailer attached to it.

And when I added the tuner from 5 star tuning a year later it really woke up the V-10! it shifted the way it should have from the factory! Fords shift strategy leaves a lot to be desired. and here again because of its ability to hold each gear longer when upshifting (which uses the available power more efficiently, meaning no short shifting) and its ability to hold OD a bit longer reducing downshifting, I gained another .3 mpg. yes these are real world numbers and not something I dreamed up.
And every time I see the RPM drop on the 1-2 and 2-3 shift it makes me sick, that's how terrible it is at transferring power!

One final thing I did was add an air deflector to push the air up and over the trailer. and this again gave me another .4-.5 mpg. So When I started out I was getting around 6.3 with my V-10. I can now get 7.5-7.7 all day. if its not windy and I slow down I get 8, although that is very rare that's its not practical to go by.

Now with all that said. the newer 6,8,9 and 10 speed transmission are very efficient at transferring power. so unless your towing really heavy you are not going to see much of a change.

[mtofell1]

ol' yeller wrote:
Gas mileage didn't improve or degrade enough to notice.

I think this is what a lot of people need to read and reread. Whenever gearing discussions come up, the whole MPG thing is way overstated. Unless you are doing a very drastic change it likely won't be noticed.

[ol__yeller]

My experience was with a '99 Ford Superduty F250 with a V10 Supercab, 2WD. I changed out the 373 gears for 430's several years ago. We were towing a bumper pull that weighed around 7,500# loaded. Before the change, the engine would constantly downshift at even the slightest hill or need for acceleration. After the change the engine stayed longer in its sweet spot without dropping a gear so easily. It was expensive even for 2WD but I also added limited slip and it was like an entirely different truck handling wise. Probably not a great investment financially but for the grins, it was well worth it. Did I mention how much better the truck stepped out from a stop as well? Gas mileage didn't improve or degrade enough to notice.

[patperry2766]

What part of Texas do you live in?

A lot of the bigger towns have 4x4 shops. Might be worth checking with them. Years ago, I had a Toyota 4x4 that I went with bigger tires on. I did the work myself to remove the axles and pumpkin (wasn't really that hard), bought the parts and they put then in the pumpkin and shimmed it for about $100. Probably more now.

Company is 4 wheel parts and they have stores in DFW, Austin, San Antonio, Houston, Beaumont and McAllen. Any good axle shop should be able to easily do the work.