Gear Vendors Overdrive

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BeBop
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Posts: 22
Joined: Tue Mar 27, 2007 10:53 am
Location: Bakersfield, CA

Gear Vendors Overdrive

Postby BeBop » Tue Feb 12, 2013 7:49 pm

Hello Pupsters:

I did a search of the forums and the topic of Gear Vendors overdrives has come up before, but it appears nobody has gone that route. I have long wanted to put an overdrive in my 1982 diesel 5 speed longbed. It looks like it was designed for it. Well, I found an older divorced style J type Gear Vendors overdrive in good condition and had it rebuilt by Maximum Overdrive in Aromas, California. It now has all new bearings, seals, gaskets and a new yoke. I have a hot rod fabrication guy ready to install the unit. To engage the overdrive, I intend to install a manual toggle switch in the unused knock out panel next to the steering column. I have heard conflicting advice as to what amperage the circuit should be. I don't expect to increase my mpg substantially, but even a couple of miles per gallon would be nice and having the engine run at a lower rpm while cruising will certainly be nice. I wanted to share this with the P'up community to see if anyone has any advice they would like to share before I jump in.

To see a pic, go to
http://farm9.staticflickr.com/8512/8469893404_2bb0397bf0_b.jpg

The unit currently has a flat plate cover on the bottom. I intend on installing a high capacity, finned aluminum sump that will add about a quart extra volume.

--Eric
1982 diesel P'up DLX 5 speed longbed

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QuantumRift
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Posts: 157
Joined: Sun Dec 09, 2012 5:19 pm

Re: Gear Vendors Overdrive

Postby QuantumRift » Tue Feb 12, 2013 8:55 pm

Well, only you can decide if it's 'worth' price for the return on the cost. What's the return on your cost? Here's how you calculate it: This is just an example, but your figures plugged in here will work.

20,000 miles driven in a year divided by 20 mpg = 1,000 gallons of diesel fuel used per year.

1,000 X $4.00 (for each gallon of diesel fuel) = $4000 spent on fuel for the year.

Now, we are just guessing that you will get 2 mpg more per gallon, so we just redo the calculations:

20,000 miles per year divided by 22 mpg = 909 gallons of fuel per year.

Multiply that figure, 909, by $4.00 per gallon for an estimate of $3,636 year for fuel.

Now take $4000 (before modifications) and subtract $3,636 (after modifications) to find your yearly fuel savings, $364.

Divide the cost of modifications, $1,000, by the savings, $364, to determine how long it will take to recover the expense of updates. In this case the answer is 2.75 (2 years, 8 months) years, or 20,000 miles x 2.75 = 54,945 miles. Will you keep the truck that much longer?

If you drive fewer miles each year, and if the per gallon savings are less, it will take more time to recover your expenses. On the other hand, if gas prices keep climbing upwards, you may see a return in less time.

To get a better picture, just plug in your figures above (miles driven per year, cost of your modification, and price of diesel fuel).

The plus as you say is less wear on the engine, but diesels are designed to keep going and doing and going anyways... :lol: And you will be reducing your 'carbon footprint' as well, which is good for the environment. [APPLAUSE]




BeBop wrote:Hello Pupsters:

I did a search of the forums and the topic of Gear Vendors overdrives has come up before, but it appears nobody has gone that route. I have long wanted to put an overdrive in my 1982 diesel 5 speed longbed. It looks like it was designed for it. Well, I found an older divorced style J type Gear Vendors overdrive in good condition and had it rebuilt by Maximum Overdrive in Aromas, California. It now has all new bearings, seals, gaskets and a new yoke. I have a hot rod fabrication guy ready to install the unit. To engage the overdrive, I intend to install a manual toggle switch in the unused knock out panel next to the steering column. I have heard conflicting advice as to what amperage the circuit should be. I don't expect to increase my mpg substantially, but even a couple of miles per gallon would be nice and having the engine run at a lower rpm while cruising will certainly be nice. I wanted to share this with the P'up community to see if anyone has any advice they would like to share before I jump in.

To see a pic, go to
http://farm9.staticflickr.com/8512/8469893404_2bb0397bf0_b.jpg

The unit currently has a flat plate cover on the bottom. I intend on installing a high capacity, finned aluminum sump that will add about a quart extra volume.

--Eric
"When he drives a new car off the lot, it increases in value."
"His word IS his passport."


1990 LS SpaceCab 4x4 2.6L (Manufactured in Japan, September 1989)
206,000 miles. Owned since 15 miles. Paid $15K, Oct 1989.

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Halden
Regular Member
Posts: 2076
Joined: Thu Mar 29, 2012 5:20 pm
Location: Rexburg, Idaho
Isuzu vehicle(s): 1983 Diesel LS Long Bed 4x4

Re: Gear Vendors Overdrive

Postby Halden » Sun Feb 17, 2013 7:45 pm

That will be interesting to see what having a double overdrive will do... If I remember correctly Jerry lemond informed us at the meet back in June that the reasons these early 5 speeds would break down was because people were sticking them into overdrive too soon and putting the RPMs too low which would really ware out one of the bearings or something overtime do to the violence of the combustion. It would bust it up and then the gears wouldn't line up correctly and they'd machine themselves away.

Also, just my opinion here, these are little diesels so its not like peak torque is down at 1500/1800 RPMs. For our c223s it's at 2200, I don't know how far that peak torque goes up in the RPMs but mine really is very efficient at 2700-3000 and doesn't like staying to far below 2200 when I am moving at a higher speed... It seems pretty happy higher up, just not too high!

-Halden
1983 Long Bed Diesel 4x4 LS


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