[SteveBaz]

The situation

When new 265 70r 16's All I have done is put 295 (33+") BFG's. OEM 355 gears.

The truck luggs down when pulling big load.

How much and about what gear set do I use front and rear diffs? Do I need any conversion kits? Should I just find some 411 axles and swap them out. What do I need to accually do to get my trucks torq back.?

Thanks in advance,

BAZ...

 

[ryhed]

410 gears, swap the front axle to a solid axle.

 

[SteveBaz]

410 gears, swap the front axle to a solid axle.

I not sure what you mean? :nono:

I have solid axle Dana 60's front and rear with stock 355 gears , so with my size tires 295 75r 16's what will I be with 410's in my diffs?

There must be a formula some where, right:dunno:

Has anyone done this to their truck? Someone must have done it because, when you put 44'' mudders you sure are not running stock gears! To get torq back you need to offset the tire size by changing the gears that drive that size tires with no strain on driveline, u-joints and your entire drivetrain system really. Am I thinking right because that how I have it in my head??

BAZ...

 

[Nit]

No you're right in the head :thumbsup:, diff gears or drop a gear when pulling, you re choice.

Your best option is to change them out for the 4.10's, a good shop will sell and install new ones adn give you a little something for your old ones. You will just notice an RPM change.

Your other option is a gear vendor OD unit, which would only work in 2wd but allow you to under drive or overdrive , it would be like a split rear end.

Or the cheapest is to get smaller tires again, but that's just gay.

Glad to see you're keeping the old beast running.

Craig

 

[caryt]

Steve...get a TS chip with TW tunes and a D66 or a modded H2e...will get the job done even with those gears!

 

[SteveBaz]

Steve...get a TS chip with TW tunes and a D66 or a modded H2e...will get the job done even with those gears!

What does a chip have to do with EGT's. Before doing that I would put an intercooler on or propane injection. I have DYNOed @ 290HP with tons of Torq where the wheels meet the pavement. I need to re-gear so my lugging is not effecting my engine temps. If I put 4:10's in it I can get back closer to stock 3:55 I started with. I may not be able to go as fast but my truck will do at least 130 mph so big deal I will only be able to get a 8,000 lbs truck to 115mph :jester:

BAZ...

 

[ryhed]

Does this help?

Here's the equation for finding what your car's MPH will be with any given RPM, given gear ratio, tranny ratio, and tire height:

(RPM x Tire Height) / (Rear Gear ratio x Tranny gear ratio x 336) = MPH

And it's pretty simple to find what your RPM will be at any give MPH also by solving for the RPM:

(MPH x Rear gear ratio x Tranny gear ratio x 336) / Tire Height = RPM


Example: a car at 75mph with a 4.10 gear and a .62 overdrive in 5th gear and 26" tires=

(75 x 4.10 x .62 x 336) / 26 = 2463 RPM

 

[action4478]

I assume you calibrated the speedo ...

 

[SteveBaz]

Does this help?

Here's the equation for finding what your car's MPH will be with any given RPM, given gear ratio, tranny ratio, and tire height:

(RPM x Tire Height) / (Rear Gear ratio x Tranny gear ratio x 336) = MPH

And it's pretty simple to find what your RPM will be at any give MPH also by solving for the RPM:

(MPH x Rear gear ratio x Tranny gear ratio x 336) / Tire Height = RPM


Example: a car at 75mph with a 4.10 gear and a .62 overdrive in 5th gear and 26" tires=

(75 x 4.10 x .62 x 336) / 26 = 2463 RPM

ryhed perfect thanks for the formula.

BAZ....

 

[pstrahin]

Hi Steve, been reading your posts for several years, and here is my experience with my 95 PSD, truck came with 4.11's. My usage of this vehicle used to be 10% towing, 90% transportation. To help improve economy and fuel mileage, during the first oil price hike I pulled out the 4.11's and installed 3.55's, my plan being to drop down a gear if needed when towing. I used to tach 2400 RPM @ 70 Mph, and now I tach 1950 RPM at the same speed. I used to tow in overdrive, and I was surprised to find out I can still use overdrive most of the time when towing. Fuel economy still stinks, maybe a little better. The best part? Much less engine noise, nice and quiet on the road, and now sounds and drives more like the RPM range of the big rigs. Did not appear to lose much pulling torque. BTW, my solution to robber oil companies and the economy is to quit driving the truck for transportation. Less than 500 miles the last 6 months, and now and for the duration a SUV. (Seldom Used Vehicle) Get a solar battery charger and let it sit most of the time.

Best regards,

Dr Phil