Engine/Transmission (1998.5 - 2002) Gear Swap info?

[dspoon]

I am looking into doing a gear swap from my 3. 55 to a 3. 73 I need a little get up and go when I head to the hills pulling my FW 10000 plus lbs. Wanted to know if anyone has made this swap and were there any pros and cons to it looking for opinions do's and dont's and pros and cons. The tires I am running are 305/70/16 I know that hurts me some but I like the look.

 

[HBarlow]

The Dana 70 or 80 differentials used in the Gen II trucks offered either 3. 54 or 4. 10 gear sets. I don't know if 3. 73 was available from aftermarket suppliers but think not.

Your best bet with a soft slushbox and big tires pulling a 10k trailer would be the 4. 10 gearset anyway. The change from 3. 54 to 4. 10 would provide much more starting torque to the ground and the overdrive ratio in the 47RE would still give good highway cruise rpm and fuel mileage.

 

[vahunters]

Glad you asked that question. I have the 3. 54s and they are pretty weak for this engine.
In a previous non diesel truck I owned , I went from stock 3. 55s to 4. 56s when I got a small lift and 35" tires. The difference in get up and go was amazing and at highway speeds the truck ran nice and no issues. I put in Yukon gears and would go that route again when I go to 4:10's

 

[dspoon]

Thinks for the input HBarlow you are right about 3. 54 or 4. 10 for those years and yes you can get aftermarket for our years just wanted to get some input before I make the move thanks for the input.

 

[Mhannink]

3. 73 would probably be just right i ran 35s with 4. 10s and still wanted 3. 54s but i have a manual trans the 373 is a nice middle range gear for beefier tires and still offers the performance of both 410 and 354

 

[SHobbs]

I plan on the 3. 55 to 3. 73 swap and yes it is doable. I have talked with two shops about it both using Dana parts, the cost is between $750-$1000.

 

[SRadke]

With a stock converter and oversize tire, I'd definitely go to a 4:10, not a 3:73.

-Scott

 

[dspoon]

Thanks everone for the help and opinions

 

[cerberusiam]

With a stock converter and oversize tire, I'd definitely go to a 4:10, not a 3:73.



-Scott

Yep, what he said.



With an auto and those tires, 4. 10's for sure. The 3. 73's leave a little to be desired towing with tires over 32. 5-33 inches tall.

 

[SnoKing]

4:10's with the auto are the best for towing! SNOKING

 

[dspoon]

Will 4:10's kill my gas millage this is a daily driver to.

 

[SnoKing]

I get around 15 mpg in mixed daily driving. 18 to 20 on the freeway depending on speed. 11-12. 5 towing a tall 12. 2K 5th wheel. Trucks are similar, I however have the front axle CAD and custom DTT transmission. A 3:54 to 3:73 is not enough of a gear change to justify the cost. Find someone close by with 4:10 and give it a test drive.



I tow at around 63 MPH at 2000 RPM. It runs up and down most freeway hills in OD without slowing down. Climbs most mountain passes in 3rd at 55 MPH just fine. I am at around 325/650 at the rear wheels.



I did find that my throttle cable had too much free play and cruise control had more power than my foot. I put a couple fishing split sinkers on the cab end of the cable to take out extra slack. If you pick up the pedal with your hand and it comes up a inch or more you have the same issue, which is common on these trucks. When you pick up the pedal you will see the center cable stick out of the while plastic guide on the top of the pedal. A couple nylon tie wraps will allow you to test for more power. Fishing weights are a better long term fix. I dyno'd below 300/600 before I fixed the throttle and switched to the PDR35-12W turbo.



SNOKING

 

[rasteck]

Comparing 62 mph it looks like your RPMs would be:

3. 55 - 1574

3. 73 - 1658

4. 10 - 1823



As said previously, it doesn't look like there's enough of a change between the 3. 55 and 3. 73.



4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators

 

[WestTN]

In general, if you only need to step up or down one ratio, you don't need to do it at all. Not enough change to warrent the cost.

 

[tempforce]

1800-2000 rpm is the best for mpg and power combo.

 

[MChrist]

OK, this is weird... the rear just went out in my 98. 5 cab/chassis with 3. 55 rear end. Since the truck is super heavy and does all stop and go driving, I decided to go up to the 4. 10 and was told I needed a whole new housing, because the 4. 10 wouldn't fit!! Cost of new rear end with gears complete was around $2600. Did I get taken? I think it's the Dana 80.

 

[HBarlow]

I believe you were taken.

 

[MChrist]

I've read several posts now from other sites that say the same thing. . if swapping from 3. 55 to 4. 10, you do require a different carrier. In my case, my truck's rear end has seen more abuse than most. New probably isn't a bad thing.

 

[MChrist]

Hey Harvey, how many miles on your 'wing? I've just eclipsed 30,000 on my black '03!! I truly LOVE this bike!!

 

[SnoKing]

OK, this is weird... the rear just went out in my 98. 5 cab/chassis with 3. 55 rear end. Since the truck is super heavy and does all stop and go driving, I decided to go up to the 4. 10 and was told I needed a whole new housing, because the 4. 10 wouldn't fit!! Cost of new rear end with gears complete was around $2600. Did I get taken? I think it's the Dana 80.

That's about the price of doing two ends on a 4x4. You may have needed a new carrier that ring gear bolts to, however you did not need a new housing!



SNOKING