727 Low Gear Set

gulfdawg

gulfdawg

Member
I have heard various arguments for and against the 727 low gear set. I have even heard it doesnt exist. I am still not sure if it was available in rv transmissions. Anyway, it is suposed to be ideal for heavier, lower horsepower engines. Now the Scout guys May not need this but I have a truck and it is pretty heavy and I really believe this could help me. For 500 dollars it is roughly the same price as doing gears in the diffs. I was just wondering if anyone has had any experience, good or bad, with this gear set.
 
edit: a true 727 low gear set is an aftermarket item. I've never found any evidence it exists as a chrysler-source setup, though I've yet to get into all applications of that trans. I'm not saying it was never used oem by chrysler in production, I'm just saying I've not turned up any definitive part number or tech info with factual data and/or drawings/pics. Involved part number differences yes...but that is because of the four vs. Three gear planetary parts differences.

And the gear sets available don't come close to providing the advantages of a simple gearing change in the axles.

A "low gear" planetary set along with numerically high axle gears would be advantageous in extreme offroad or vocational truck operation. Especially if cost is no object.

The core dodge motorhome 727 transmission that I built for maranda's "pink" mud drag rig supposedly had that phantom low gear planetary set in it,...but the only difference in the motorhome units (and same for IH motorhome apps) is a four gear planetary setup instead of the three gear setup used in standard duty 727 apps (including all IH stuff except motorhome):
 

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I do agree that a change in the axles would be easier. I like my cruising rpm on the free way, 2400 rpm @ 65. I would just like a little more on the lower end and the low gear set seems to be the answer? A lower first and second gear would give me a little more on the bottom
 
I offer a 727 low gear set. It changes your existing ratio of 246 1st and 146 2nd to 275 first and 154 2nd.
This is a new planetary set. $795 at this time,special order only, no core required!
My experience with them is very good!

Isa
 
I installed a *low gearset* planetary (4-pinion) about 10 years ago when I rebuilt my Scout iis 727. It was $395 from jvx, inc. Of memphis, tn. For me, the cost was worth it. My Scout is set up with a Dana 300 t-case, 3.73 axle gears, and 33x9.50 tires. With the axle gear ratio and tire size, my freeway speed/engine rpm relationship is perfect (about 2500 rpm at 60mph). The peak torque of my 304 is in the 2400-2600 rpm range.

For my mild off-pavement excursions, the low 1st gear and the 4l ratio of the Dana 300 work quite well for me.

If I had lower (higher numerically) axle gears, my rpms would be higher than the engine's peak torque range at my normal highway cruise speeds, and my fuel economy would suffer.
 
I agree with eriks' take on this. I installed a 4 pinion low gear planetary about 7 years ago. I paid around $600 or so and it was worth it. I also installed a tera low 3.15:1 gearset in my Dana 20. With 3.54:1 detroit e-lockers and 31:10-50 tires I get a good balance of highway and offroad performance.
 
The 31" tires/3.54 axle gears or 33" tires/3.73 axle gears is a good all-around combination. I changed from the former to the latter, and my speedo is still dead-on accurate.

A teralow 3.15:1 Scout kit (auto trans) for the Dana 20 is on my ultimate wish list. I'd like to rebuild one of my spare 20s with it. Maybe I could finance it with the sale of my Scout d-300?
 
My change was from 3.08:1 to 3.54's so I'm always reading 5mph over actual speed. Some day I'll have a new speedo reduction gear made up but in the meantime I can feel like I'm making good time while driving.
The tera-low for the 727 auto I hear is off the shelf. The bull gear is totaly unique and no longer made. Might be worth the exploration though, my stock ratio worked out to 15:1 and now I'm at 30:1. My primary goal was to get off the brakes on long downgrades and it does a good job of that. Coming down from laurel lakes south of mammoth lake was a heck of a ride. The stock gearing would have me at 20mph in first-low! Both feet on the brake pedal and my butt an inch off the seat!
 
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