I was just day dreaming today while celebrating at the inlaws and was wondering why no truck maker offers a 2 speed rear end or a "quick change" like the race cars use, rear end option.You would think it could give the best of both worlds better mpg and better towing/hauling power. With a quick change you could tailor the output of you truck to the anticipated terrain and the weight of the trailer.

Maybe not exactly what you are referring to, but Gear Vendors has something that might work.

In the type of vehicle you are referring to:A Multi-speed rear end (Gear Vendor's fine products) would do almost the same thing as the 5 and 6 speed Allison transmission does by locking out 1 or 2 of the overdrives. The result is more engine RPM's when overdrives are locked out than when they are engaged to have the same vehicle velocity. Not an exact relationship but very close! What does a 2 speed axle or rear end do? When in low range it requires higher engine RPM's to turn the drive wheels at the same RPM which means the same MPH.The general rule of thumb is to keep the engine RPM as low as practical when driving at highway speeds. Easy when driving unloaded. More weight being moved, climbing up hill, bucking a head wind or an increased wind resistance on level ground requires more force to the drive wheels than when unloaded. An internal combustion engine requires enough fuel in the cylinder to explode. Too little fuel (lean) and there will be a low power explosion or no explosion at all. The faster the engine crank rotates, the more fuel it consumes. After engine gear reductions be it a 2 speed axle, transmission gearing, or rear ratio controls engine RPM at a given vehicle velocity. It's the BTU's (heat) of expansion in the correct fuel/air mixture ignited factored by compression ratios that controls the amount of force driving the piston down/away which turns the crank and the drive wheels. Less fuel, less force and less RPM.

The advantage of a 2 speed or quick change rear end is that when you are towing you could pick a rear ratio that gives you 6 useable towing gears instead of 4-5. It would also give you more available power at most road speeds.When not towing you would be back to a ratio that gives you good fuel economy and lowers rpm for empty driving.The gear vendors stuff is nice and also expensive. But with the coming 9 and 10 speed transmissions soon we will have most of these advantages.

Many years ago, such rear axles were available. They were quite common in Fords after WWII. They were Columbia 2-speed rear axles. They were GREAT!Two and three speed "Brownies" (auxiliary transmissions) and rear axles were very common in trucks from ton and a half or two ton on up. Years ago, I drove a Ford F-4 (IIRC) that had an electric shift two speed rear axle with that horrible 4 speed straight tooth transmission. I was young then, and double clutching didn't bother me.

Alison makes 2 speed rear ends. You can not shift them when driving like you want and would give the the best of both worlds.A couple of companies make a 2 speed gear box that bolts tot he back of transmissions. I don't know how they would work with autos, but I had one on my 68 C10 3 speed on the column and loved it.Last I read the major manufacturers were only going to offer autos in there HD lines. I don't see them making anything over a 6 speed auto because of size. I could see a 8 or 10 speed if the made split shifts.Size wise on a manual would also be huge at 9 or 10 speeds unless it was a split shift.

Why not a 2 speed or quick change rear end option

Bedlam
Moderator
Dec 27, 2013
Many of the off road side by side vehicles do not use a transfer case. The use a primary transmission driving two dual-speed differentials (that may also have the ability to disengage or fully lock up).

The ones coming of China use a mini car engine with a locked manual transaxle (no differential). The engine and transmission sit longitudinally and each transaxle output drives a shaft to the axle differentials.

This is not much different than what you are asking for except the ratios are for high and low range instead of tow and economy.

06Fargo wrote:
At the risk of taking a rashin' - this is a great idea - gear reduction as close as possible to the wheel ends gives the greatest benefit in pulling power vs more transmission speeds < overdrive.

My dune buggy is based off a 1200cc VW Bus engine and chassis it uses gear reduction units at the hubs to allow a small engine move a large vehicle. The dune buggy is much lighter than the Bus, but the gearing allows it to have 33" rear tires with out bogging out in sand.
monkey44
Nomad II
Dec 27, 2013
I recall our old farm truck - the dump - had dual-position RE, and we had a shift lever (like the standard 4x4 lever) above the 'drive hump' ... we could shift into a very low 'grunt gear' in the RE and really get some pull-power when loaded and towing a tractor uphill. It was not a big deal to shift back and forth, although the lower gear was really low and non-syncro, so we had to stop dead to shift into or out. But once into one or the other, the gear shifting acted like any other tranny ... first through fourth, in the old GMC two-ton, with the 'granny gear' first.

As simple as it was, I can see technology easily re-creating that gear-transfer into a synchro-tranny with higher gears that could shift-on-the-fly and put what is now a four or five speed drive train into a ten or twelve speed drive train. I know, a lot of shifting, but if you think it through, once you get into one or the other, it's actually still shifting from first - fifth anyway.

I'm just as sure (for enough money) the automakers can build a auto tranny that will do it too. That means ONE gear shift gives five gear ratios each. Instead of ten or twelve gear combinations. I'm no engineer, so can't even begin to draw this out, but in my brain, it worked well on the farm for power, so I can imagine it can't work in reverse for more mileage.

Probably similar to the 'low range' vs 'high range' in the electronic 4x4 today, except instead of a power gain, it would become a mileage gain.

Probably not been into the minds of the auto-engineers until now as the price of fuel gets everyone's attention, and mileage becomes a more important factor in new truck purchase than what was once the power side of the advertising and use potential in a HD pick-up truck.
carringb
Explorer
Dec 27, 2013
Wes Tausend wrote:

Thanks for the reinforcement. I did do some preliminary looking but it was inconclusive, especially shift points and holding a selected gear. I guess I would trust Banks Power over and above unfamiliar products, whatever features they may offer.

The power seems ok for the TT, but a little more couldn't hurt, maybe at least match the V-10 hp. There is probably not much sense keeping it stock as the untouched noisy old 7.3 rapidly ages beyond current populararity during my ownership.

I wonder if computer shift points wouldn't be even further off with a Gear Vendors.

Wes
...

You can add a simple TCC lockup override. It's just a matter finding the correct wire to tap in the transmission harness.

I added both the Banks Transcommand and Predator tuner to mine. The Banks allows earlier T/C lockup. It will even lockup in 1st under heavy throttle. (I'm not sure the diesel programming allows that however). I've also reduce my OD shift point which allows me to climb 10% grades in OD as low as 40 MPH, turning barely 1200 RPM.
noteven
Explorer III
Dec 27, 2013
At the risk of taking a rashin' - this is a great idea - gear reduction as close as possible to the wheel ends gives the greatest benefit in pulling power vs more transmission speeds < overdrive.
Wes_Tausend
Explorer
Dec 27, 2013
bmanning wrote:
Wes Tausend wrote:
...

I'd be satisfied with the ability to force an earlier shift, and lock-up, on the 4R100 auto on our 2000 F-250 7.3L. As it is, it does not shift to OD, nor converter lock-up, until about 40 mph even when there is virtually no load. If I had a manual, I'd be short-shifting around town while running empty.

Wes
...

There at least used to be (likely still are) products on the market that can allow the driver to dictate TC lockup. Maybe Banks Trans Command, something like that? Can't speak to their cost or quality but they do exist.

When I had my 2002 7.3L I always had a feeling that the stock 4R100 left some performance on the table and if I'd have kept it a built trans would've definitely been in the plans.

Thanks for the reinforcement. I did do some preliminary looking but it was inconclusive, especially shift points and holding a selected gear. I guess I would trust Banks Power over and above unfamiliar products, whatever features they may offer.

The power seems ok for the TT, but a little more couldn't hurt, maybe at least match the V-10 hp. There is probably not much sense keeping it stock as the untouched noisy old 7.3 rapidly ages beyond current populararity during my ownership.

I wonder if computer shift points wouldn't be even further off with a Gear Vendors.

Wes
...
MX-RV
Explorer
Dec 27, 2013
So your jeep still has a "transfer case" it's just built into a transaxle mounted directly to the engine. If you look on the video the front drive shafts come directly from the transaxle as does the "prop shaft" as he calls it.
I'm impressed to see its a 9 speed. I'd like to see the 2500's 250's come with 9 or 12 speeds. Weighted at the bottom for torq and at the top for highway miledge. I saw a you tube vid once of a f350 the guy had remade the bell housing on a freight liner 16 or 18s it wa pretty sweet. Mind you he did a no throttle take off from a stop in 4th if I recall. Maybe for most uses around here that's a little low. I'm willing to bet he's not got much more top end than the stock was.
bmanning
Explorer
Dec 27, 2013
Wes Tausend wrote:
...

I'd be satisfied with the ability to force an earlier shift, and lock-up, on the 4R100 auto on our 2000 F-250 7.3L. As it is, it does not shift to OD, nor converter lock-up, until about 40 mph even when there is virtually no load. If I had a manual, I'd be short-shifting around town while running empty.

Wes
...

There at least used to be (likely still are) products on the market that can allow the driver to dictate TC lockup. Maybe Banks Trans Command, something like that? Can't speak to their cost or quality but they do exist.

When I had my 2002 7.3L I always had a feeling that the stock 4R100 left some performance on the table and if I'd have kept it a built trans would've definitely been in the plans.
ib516
Explorer II
Dec 27, 2013
Sorry for the off topic...

It has a 2 speed front and rear axle, each with the same regular, and 2.92:1 ratio in each diff. The rear also has an e-locker, and it has a 9 speed auto trans. Complex system.

My point was that the technology is there to have 2 speed axles in tow vehicles, and I don't think that it will be long before your 2500 and 3500s have the same technology.

Start around 4:30 in This video
Wes_Tausend
Explorer
Dec 27, 2013
...

I'd be satisfied with the ability to force an earlier shift, and lock-up, on the 4R100 auto on our 2000 F-250 7.3L. As it is, it does not shift to OD, nor converter lock-up, until about 40 mph even when there is virtually no load. If I had a manual, I'd be short-shifting around town while running empty.

Wes
...
jauguston
Explorer
Dec 27, 2013
516,

Do you have both 4 high and 4 low?