I have read you guys with Gear Venders talking about splitting gears. I guess I am not sure how to fully utilize my Gear Venders. I typically manually engage mine with the dimmer type switch once I get to speed. It has the auto mode, but the shifting is so hard that I don't use it that way. On the unit it says it is an overdrive/underive unit. With that said, how do I effectively use this system? Thanks for the information.

 

The splitting of the gears goes like this. 1-1.5-2-2.5-3-3.5

So you shift at the end of first gear, then when it shifts to second you shift the GV back to normal then at the end of 2nd you shift the GV.

 

Dean88-

Thanks for the response. I assume this is most effective when towing. When I am empty, I go from 1-3 so quickly that it would be useless to split the gears. Like I said before, it down shifts so hard when I disengage the GV that it seems to put too much stress on the tranny. I have left the GV in the auto mode when pulling before and it has gone from 3 over pulling and shifted down and pulled better. I was told that I should not use the GV when pulling though. I do have a tranny cooler. What are your thoughts?

 

According to the Gear Vendors site they no longer have an underdrive.

Here is a link to their towing info for a 3 speed Ford automatic tranny.
While towing, the ability to shift 1/2 gears , 3rd over to 3rd to 2nd over to 2nd to 1st over to first keeps the engine RPM in the power band.

Ever pull a hill, 2nd was to slow, but shifting to 3rd dropped the RPM below your effective power range, so you had to drop right back to 2nd?

With the Gear Vendors, 2nd overdrive is right between 2nd and 3rd, so it would be a better gear to shift to than 3rd would be.

Gear Vendors Under/Overdrive Ford 2-Wheel Drive 3-Speed Automatic.

 

from what I understand you would only use it for towing. But I would use the overdrive all the time for fuel economy reasons. When you are towing there are sometimes you need to downshift but don't want to go down a whole gear thats when the gv comes in nice. I had a 96 dodge 5 speed and there are some hills arround here that I would need to go down to 3rd gear towing my toy hauler, but there is such a huge hole between 3rd and 4th - a gv would heve ben nice there to split the gears

 

Thanks for the info guys. Do you concur that it is ok to use the GV while towing? Do you believe there is any damage to the tranny while towing in OD.

 

I would install a tranny temp gauge.

If it starts getting hot, drop a gear or get a bigger cooler.

 

Every manual equipped diesel I've ever towed with needed a "3.5" gear.

 

Definitely follow what Dave said about the gauge. I can't say for sure, but I think the GV on my Cummins conversion is adding to the problem of keeping the auto box alive. The fluid burned quickly, and I think the converter died. I'm going to be swapping it to an NV4500 now, just because 2 trannies in about as many years is too much...

 

The reason Gear Vendor calls it underdrive/overdrive is because when the unit is engaged in first gear it's called first and over, or second and under. Disengage the unit, trans shifts to second (direct), engage and it's second and over or third and under, next shift is third (again direct) then third over (for a C-6)

It really is a bit confusing for it to be advertised the way it is as an underdrive/overdrive.

Before the RoadRanger trannies became popular in semi's, most trucks had 2 trannies. The main box and a brownie or auxiliary. The main could be a 4, 5 or 6 speed with a short or long 5th. Brownie could be a 3 or 4 speed, I don't remember if there was a 5 or 6 speed brownie. The main box would be first through fifth and the 4 speed brownie starting in the lowest gear would be deep under, under, direct, over. Usually didn't use deep under except in first and to get a real heavy load started.

Generally a guy skipped a few gears here and there depending on the engine, load and terrain but as you can see there are many combinations that could be used.

Our forum leader knows all about skipping n splitting gears. I have not run a truck with a set of sticks for probably 20 years.

At any rate, that's where under/direct/over drive terms came from!

 

I learned on a 5x4 setup.

20 gears to the front, 4 gears in reverse.
Logging in the montains here, you used them all at some point on every load you hauled to the mill.

I had the pleasure of showing some young truck drivers how they work in 07, and what a difference they made if you knew how to use twin sticks.
Before that they always wondered why I could shift a manual so well with my left hand.

If you want to see what it would be like, take a drive in your four speed and put your right arm behind your back and leave it there.
Main tranny was left hand shifting, right hand for the auxiliary over by the passenger seat or behind and to the right of the drivers seat depending on the truck you were in.

US Gear makes the under drive and an over drive, but only the three or four speed auxiliary tranny has both in the same box.

 

I pulled a 10K lb, 28' trailer up the Cajon Pass with Gearvender engaged.

I pulled a 21' Toyhauler 2200 miles from San Diego to Florida with Gearvender engaged.

never once had a problem with the trans overheating.

Gearvender recommends replacing the oil once a year in the unit though.
Last update I received from GV was GM#12346190 or Mopar #04874459 synthetic gear oil

for a firmer shift use GM#1052271 petroleum based oil.

Love it for long distance travel unloaded as well. they call it double overdrive witch keeps my RPM's around 2000 at highway speed with 35" tires and 4.10 gears.