Quote:
Originally Posted by jkib
I was looking at the specs of the 07 Tundra and noticed that the 4.7 has the 9.5" 4.10 gears, and with this it is rated to tow about 1000lbs more than the 05/06. I believe the transmission is the same 5 speed in both models. Besides brake differences, is this the only reason for the increase in tow capacity?
If one were to install the rearend of the new unit into the older model, or regear, would that be sufficient to increase the capacity of say my 05 DC?
While looking at a new 07 with the 4.7 this past weekend, I noticed that the rearend assy looked the same as that in my 05 as far as size goes.
Any thoughts?
Thanks
Joel
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First of all, I rather strongly doubt you'll be able to install the '07s 9.5 inch gears into your current axle (which, IIRC, has 8.25 inch gears). Probably impossible. Swapping axles would be extremely expensive and difficult, if not impossible due to other changes like truck width, frame design, suspension design, etc. You'd probably find that a trade up to an '07 would cost less than a parts swap.
That being said, you might be able to install the 4.91 gears from an '04 DC, or better yet, the 4.30 gears from 4WD Automatic V6 (Taco or Tundra)...which is what I did.
If you do change the axle ratio, you'll definitely get more rear wheel torque (5% more with 4.10, 10% more with 4.30). I can speak from experience that 4.30 gears make mountain towing a heckuva lot more enjoyable (far fewer downshifts, much better acceleration)...but they also really cut down the top end speed of the intermediate gears. For instance, my '03 (4sp tranny) now redlines at 65 mph in 2nd gear (used to be 72 mph) and that means upshifts sometimes happen way too soon. And gas mileage dropped a bit...maybe 3 to 5%, more at higher speeds on flat roads.
As for actually increasing the
rated tow capacity of your truck, that's hard to say. If the axle gearing was the only thing suppressing tow capacity, then lower (higher numeric) gearing definitely will increase the tow capacity. Such is often the case for domestic trucks which can be had with several different axle ratios...regearing to one of the lower factory ratios will increase the tow capacity to whatever the factory rating is for a truck that was made with that lower ratio. However, there's definitely more to this than just the ratio...the fact that Toyota also increased the ring size in the differential by more than an inch on the '07 4.7L engines also undoubtedly increased the diff's ability to transfer torque and handle a heavier tow load. And don't forget that the '07s also have much stronger frames and hitches than the '05s...the whole truck was significantly beefed up, especially for towing.
Bottom line: Regearing as I did to get better hill climbing and acceleration capability
with your existing trailer (within the published GCWR specs) does work and is safe. Regearing to increase your truck's actual GCWR/tow capacity, absent factory specs for the exact same gearing and other aspects (like frame/hitch strength), is going into pretty dangerous territory, IMHO.
Tundra 05/06 vs 07 Reargears
Linear Mode
