Can my truck tow this?

Terryallan wrote:

My contention is that a lower gear will give you a higher tow rating / capacity, and in fact the engineers back me up with their tow capacity numbers.
A 3.73 has a higher tow capacity / rating than does a 3.55. Why. Because the 3.73 can deliver more power to the ground at lower speeds.

According to the engineers. The idea that rear gearing no longer matters in towing is completely wrong. If that were to be true. It would not matter what rear gear was installed in the truck. They could be using 2.15 and tow the same thing. And we all know that isn't going to happen. I can tell you having just went from a 3.55 to a 3.73. there is a world of difference.

The honest truth is GM, and Ford put in high gears in most of their truck to meet the CAFE numbers mandated by the Gov. And in so doing make most of their trucks gutless. But for most customers that doesn't matter either. They are not going to use the truck to work, or tow. They just use them like a car. I have a friend that just bought a F150 with the EcoBoost, and a 3.15 rear. We were talking, and he told me. it has a low tow capacity. But he wasn't planning on towing anything any way. So it works for him.

If you are pushing the truck to it's absolute towing limit...yes, a deeper rear end will increase the tow rating. But if you are within the ratings, it won't improve the towing.

If you compare two trucks identical except: one with a 10k tow limit (& lower numerical rear end) and one with a 12.5k tow limit (& higher numerical rear end) and you are towing 7k...it really doesn't matter with modern 8-10 gear transmissions. Basically, the transmissions will pick different gears to effect the same overall gear ratio (or at least close enough it won't be noticeable when looking at engine RPM and efficiency).

This is different from the good old days of the 3 or 4 speed transmission. Yes, in those days the low numerical rear ends were about getting better MPG. Most miles ran empty and the set up the transmission around that.

Problem as soon as the engine can't hold top gear...with a 4speed, you are going from say 1.00 to 1.36 or a 36% change in gear ratio (some transmissions can be upwards of 60%). That was often WAY MORE of a drop than the engine needed, so the engine would race like mad (36% increase in RPM) to keep the RPM up high enough to maintain highway speeds. By upping the rear end, the truck could hold top gear and stay at a reasonable RPM...when towing... but will run higher RPM than needed when not towing hurting MPG.

But say the modern Ford 10 speed transmission, dropping from 10 to 9 goes from 0.63 to 0.68 or about a 7.5% change in gear ratio. So if the engine can't hold top gear and drops down, the engine sees a 7.5% RPM increase to hold the same speed and that will often be enough...if not, it can drop to 8 or 7 and so on but it can dial it in with small percentage changes. It can do this with either rear end, you will just see different gears being used for the same conditions but for the same speed the engine RPM and load will be within a few percentage points...the rear end simply doesn't matter if you are within the tow limits.