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Discussion Starter · #1 ·
I searched thru tons of forums and can't seem to find the right situation I'm in. I have a 2015 Crewmax 4x4 with 6" lift and 35's I have a TT that is 7600 and their is for sure some towing capacity loss there. I now have a drop W/D hitch and airbags in the back which help out tremendously. Now I am a family of 5 and looking at some 8000 lb TT but concerned on the performance and since there is a truck shortage in Texas, I was wondering if I upgrade my differential gears from 4.3 to 5.29 would it be worth the effort? Not real concerned about gas mileage just want to be able to hit 6th gear with ease. I'm not going thru mountains just coastal travel.

Nitro Gear Package 5.29 Gears
 

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It certainly wouldn't hurt... You are losing around 10% RPM with the 35's, plus the additional rotating mass from the heavier tires and reduced aero from the lift. 4:88's would put you back closer to stock RPM with close to an additional 2.5% RPM; 5:29's will add an additional 8% more RPM.

For example, at 65mph in 6th gear, with stock gearing and tires, you would be turning 1725RPM.

With 35's and stock gears : 1566 RPM
With 35's and 4:88's: 1790 RPM
With 35's and 5:29's: 1940 RPM
 

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Everything being perfect it would be nice to have the 5.29. There is a lot of people with 34-35 towing with the stock 4:30 ratio without any problem. I have run 285-65-20 a 34.7 and 275-65-20 a 34 for my trucks entire life. I tow about exactly what you mention except I tow from Far North Eastern California usually to the Coast the roads are up and down nothing flat like Texas.

I have stock 4:30 and no issues. Yes you have to shift gears and use the RPMs it is not a diesel. The Tundra can and will tow in 5-6 gear on the level but it is not happiest there it will be shifting a lot as there is a lot of aerodynamic drag (depending on trailer I have an Airstream) especally above 70 mph. The Tundra is happiest in 4 and maybe 5 towing. Overdrive gears tend to not be built as strong as 1-4.

The larger diameter tire do simular as an overdrive by lowering your RPMs in every gear instead of just 5-6. Yes, not the best for towing. The Tundra has a Variable Valve Timing Motor and needs some RPMs to get to the power. I would and did supercharge and gained an average of over 5 mpg with the HP tuner. I even installed ARB lockers so the labor was being done at the rear ends but I chose to stay with the 4:30 and 550 hp and 550 torque. Torque is the key to towing and gas and diesel numbers vary a lot as the power is different and the capacities are different, but I can guarantee you would not be embarrassed towing with a supercharged Tundra.
 

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Discussion Starter · #4 ·
Well i’m not ready for a supercharger just yet i was thinking since tundra is eliminating the V8 once i got the itch for a new truck thats when i would look at getting a supercharger.

Since the price on both sets of gears is the same should i just go with the 5.29 gears? Well this upgrade allow me to get back to the factory towing capacity?


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4.88 would be close to factory gearing with 35 inch. The reason I suggest the supercharger is that many people have the ability to install it themselves including the HP Tuner down load. The kit comes with great instructions and can be completed over a weekend. It is a little time consuming but can be completed with tools most people have. The superchargers are not cheep about $7000. If you save the money for an install and do the work yourself including the fact you need to run premium fuel. When I ran the numbers averaging five miles more per gallon including the difference in the price of premium it will pay for it's self in 150,000 miles. With all the new power you do not need to re-gear. If you re-gear and then decide to supercharger you will wish you did not re-gear.

Now if you re-gear, most people do not have the tools needed to accomplish this task so you most likely will need to pay to have it done. If you have someone re-gearing I would highly recomend installing a limited slip/ locker of some sort in the rear end. You may not need a front locker. I recommend the ARBs and with a compressor, compressor mount that is needed (on board air is nice to have) it will be another $1600 not installed. The front differential is a big job and time consuming (see dollar figures adding up here) At this point if you add the installation cost for the rear ends and parts cost you would be near the cost of the supercharger. A buddy with some mechanical talant, some pizza and beer and a long weekend and you have a supercharged Tundra. A supercharger on a Tundra is by far the best option available. You get to enjoy it every time you get in it.
 

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Discussion Starter · #6 ·
Well thanks for all the help, now I really got a lot to think about, where did you get your supercharger from?
 

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I went with Low Range Off Road as it is in Utah and there was no tax and as I remember free shipping. It appears that everyone sells the supercharger for the same price. It is the tax and shipping where you can save. I was going to buy direct from Magnussion but Calif tax and shipping charges was going to add about $800. Sparks Toyota in Mertal Beach SC I think also had no tax but it was about $350 for shipping. I have purchased other equipment from Low Range and always been happy. It was their staff that talked me out of changing my gear ratio to 4.88 with the supercharger and I think it was a wise decission.
 

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Discussion Starter · #8 ·
Good looking out, thanks for the help and guidance
 

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Honestly, it's not just the engine/gears you need to be concerned with. I am a Mechanical Engineer that studied vehicle dynamics and automotive design in college. I did not work in the automotive industry, but I have been a gear head all my life and I understand the dynamics of what you are asking here.

The 6" lift and larger tires significantly reduce the towing/hauling capacity of the truck. The tires/wheels are wider and move the force center point of the wheel away from the mounting flange and increases the forces applied to the wheel studs, axel shaft, and axel assembly. This no small thing. The wider wheels probably double the load on the studs and axel shafts because of the increased moment arm of the load location on the wheel.

The lift moves the center of gravity up 6" plus the additional lift of the tires. You have probably raised the center of gravity 8-10"s. And the load of the trailer on the truck is also lifted accordingly. This means the truck by itself is going to roll much easier. Add a 7000# trailer load lifted 8-10" higher, and the truck is much less stable. Add an 8000# trailer load and it's even worse.

You really should not tow a big TT like this with this set up. Go back to stock, and you are good to go. As is, I would estimate your max tow and hauling capacity is about half of stock. I know people do it all the time. Ignorance is bliss. But be warned, if you are going to tow with your set up, slow down and take it easy. I'm talking about max speeds of 50 mph and avoiding drastic moves. You have to be really careful if you tow like this.

To make this work better, you need much more stiff springs front and back, higher capacity shocks, a much larger sway bar on the front and a rear sway bar (also larger than stock), and even then, the physics of the thing is going to limit your capacity a lot. Even if you do all of this, you will never get back to what you can tow with a stock Tundra.
 

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Discussion Starter · #10 ·
Yeah, i’m thinking about just upgrading to a 3/4 ton, i wish Toyota would come out with one!!!!!!!! Honestly i’ve never had a good experience towing with a twin turbo V-6.

But i hear you i had been educated on towing with lifted truck for sure


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