Engine/Transmission (1998.5 - 2002) Going from 3;54 to 3;73 gear

[badams1]

From all that I have learned here and from local guy's I have decided to change my gearing from 3:54 to 3:73 and gain about 160 RPM at 65 MPH in OD. That would put me from 1725 to 1885 RPM +or - a little while pulling my 10k lb 5er. From what I understand the 24 V sweet spot is around 1900-2000 while pulling. I felt like I had to drive 70MPH to keep from lugging the engine, then the wind became more of a factor and I did not like driving that fast. The West Coast Differental article in TDR convinced me to make the change. I am hoping to not have to jump out of cruise at every freeway hump with this new gearing. I was getting an honest 20-22 mpg emty and I realize that I'll loose a little with the gear change but when I pull I should be better off? Hey!4;10 was just to much since I drive 90+% of the time emty. How am I doing here? Comments?



2001. 5 quad cab, lwb, auto, towing pkg, 31" Mich. tires, BD t/c, valve bdy, trq loc, Maghytec both ends, pac brake, big perma cool fan pwrd trans cooler/w 180F therm control, 4" exch, EZ, 275 inject, afe BHAF, ram cold air, Gulf Coast by pass oil filter, Amsoil everything, fuel cooler, 180F thermostat (can't tell the difference?),41 gal bed tank, serious guages on everything. I love this truck more than my HD Roadking!

 

[Rob Thomas]

This is just my opinion, for the cost it will be for the swap, wouldn't it much simpler/smarter, to just lock-out OD and run in third when towing? For the small amount of towing you do, I think its a waste of money to do the swap. When I did have an auto, I never towed in OD, but like I said, just my . 02.



Later, Rob

 

[Roger rodbolt]

Another idea might be to pick up a used set of wheels and install some shorter tires for towing. I think that a 29 or 29. 5" tire will give you the same rpm as a 3. 73 rear ratio and were OEM sized on late '90's trucks. Personally, I'd rather adjust the torque to pull at the lower rpm since our engines are so easy to modify but with an auto trans you do have to consider the load on you lockup clutch. HTH's

 

[Big White Beast]

I did it......

And I'll never regret it. I had the 4:10's to start and 3:54's after a swap. Neither was to my liking. The 3:73's keep it in the power band perfect on the freeway and they cruise around town nicely also. It is pricey but with my utility bed swapping tire sizes wasn't a viable option.



Garrett

 

[badams1]

3:54 to 3:73

Total cost of the parts and labor is less than $600 drive out, with a new OEM ring & pinion gear set from West Coast Differental and a local good expert shop. That's just about an even swap for new Mich. tires and my truck only has 13 k mi. on it. With a one year warrenty that's hard to beat. I like my present tire size and also have premium wheels. I had bids from dealers, to shops that you would not trust that ranged from $2000 to $900 but when I did the leg work I got lucky. The ring and pinionw/kit was only $240. + shipping. Tempting aint it! (E) -- email address removed --

 

[RADdodge]

I think it's a good idea. My "effective ratio" is 3. 69. I have plenty of power to pull but have to keep the speed about 62-63 mph or more, otherwise I end up having to shif down to 3rd. I knew I was going to go to some larger wheels and tires, so I figured out what running gear spec's I wanted (based on stock 3. 54 gear and standard wheels and tires) and ended up with 19. 5x285 tires and 4. 10 gears. For $600 I'd go for it!

 

[Rob Thomas]

badams1.



Going by your sig. "Mag-hy-tec at both ends" I assume you have a 4x4, which means you'll need 2 sets of ring and pinion's. So is it my understanding that $240 a set + shipping = $480+ shipping, so this shop will install both sets for $120? Or did I miss something?



Later, Rob

 

[alaterreur]

what about your spedometer, are they going to calibrate it also for that price?

 

[JBlock]

Spedo for problem

The speedo is run off the rear wheel sensor, I ask this same question a while back. I got quoted $900 plus to the gear cahnge on my 2500 4x4. $600 is steal on a four wheel drive.

 

[kchristopher]

Re: Spedo for problem

Originally posted by JBlock

$600 is steal on a four wheel drive.

$600 on a 4x4 is something you run from.

 

[badams1]

3:54 to 3:73

I am sorry I left out the 2wd on my truck sig, so it's a two wheel limited slip, D 70. The dealer here can change the tire size code for speedometer correction down two sizes if necessary, so that should put me fairly accurate on MPH after the change. Thanks guys! The parts are in the mail but keep talking.

 

[speedracer]

3.73 about right

I haven't talked myself into doing the swap, but I think 3. 73's would be just about right. 3. 54's are good running around empty or with light loads, but when pulling medium loads it would be nice to have a few more rpm without going down a whole gear. I sure wish dodge had offered that ratio.

 

[Big White Beast]

No speedo correction necessary....

Only if you change tire size. The spedo is driven from the carrier I believe. After both my swaps no adjustments were needed.



Garrett

 

[badams1]

3:54 to 3:73

Garret

That's good news because the dealer was not sure what drove the speedometer. The only thing he could offer was to reprogram for different tire size. Hummmmm! By the way the front Mag-hytec was a extra deep transmission pan.

 

[badams1]

3:54 to 3:73

Total cost was $589. drive out. I love it! 1875 RPM @ 65 MPH in OD, that's about 100 RPM higher than before. Great around town and the speedometer is still correct. Dodge should have offered this ratio long ago. QUESTION!! What is a good differental temp range while pulling in the summer? Before with 6 qts Amsoil GL5 75-90w Mag hytech and the 3:54 I was getting around 210F on a 95+F Texas day pulling 10k lb 5er? Is that OK? Haven't pulled with the new gear yet because of 500 mi break in. (using Pensoil 75-140w for break in). The guys at Houston Drive train changed out all three timpkin bearings and said they did not look that good. Could it have been the Amsoil? Truck only had 13 k miles on the dana 70. Thanks guys Wild Bill