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Jim
Dodge Dakota
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3/21/2008
23:29:42
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 Subject: Modifying O/D for better MPG's? Ideas?
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I came across this article about how to modify gears for overdrive. Yet it may of been done on an Escort, just wondering if there was something similar we could do with our A500/A518,...42,46,47 RH/RE transmissions to get better fuel mileage. He bought a used Escort Trans and took 2nd gear out and had it machined and replaced this new gear in his daily driver Escort. Is there something we can do to modify our transmissions with already existing parts such as this guy did? Maybe there is a way.
http://mypeoplepc.com/members/tleone/gears/
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N56629
Dodge Dakota
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3/22/2008
09:23:43
|  RE: Modifying O/D for better MPG's? Ideas?
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Read the article carefully. It says that the Escort OD is mounted outside of the transaxle. This is what made it relatively easy to do. Redesigning the gears on the inside would be very difficult at best or impossible.
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daddio
Dodge Dakota
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3/22/2008
10:19:17
| RE: Modifying O/D for better MPG's? Ideas?
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you could go to someone like Gear Vendors and buy an overdrive unit that mounts to the rear of the trans.
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N56629
Dodge Dakota
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3/22/2008
11:13:00
| RE: Modifying O/D for better MPG's? Ideas?
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I thought of that option but I think they run about $1500-2000. I looked at them once and figured that it would pay for itself in 50-70k miles. Basically you get a two speed rear differential.
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gen1dak
Dodge Dakota
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3/22/2008
21:39:51
| RE: Modifying O/D for better MPG's? Ideas?
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Change the ring gear in the drive axle.
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N56629
Dodge Dakota
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3/22/2008
22:17:29
| RE: Modifying O/D for better MPG's? Ideas?
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Then you lose low end performance
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jayb
Dodge Dakota
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3/27/2008
18:34:22
| RE: Modifying O/D for better MPG's? Ideas?
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"I looked at them once and figured that it would pay for itself in 50-70k miles. "
I would never do a mod that took that long to pay itself off, unless it was for fun.
That reminds me of a "buddy" who bought a brand new car and doesnt drive his truck anymore. I said, you could have just driven that truck instead of buying that car. He says " it got bad mileage." now he's paying $500 a month in a loan and higher insurance.
Bottom line.. worth it? no
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gen1dak
Dodge Dakota
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3/27/2008
20:05:00
| RE: Modifying O/D for better MPG's? Ideas?
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He's looking for better mileage. There's always a trade-off. However, due to the multiplication from the overdrive, a relatively minor change in ring gear results in a major change in final drive ratio. Do the math. Cheapest and quickest would be to buy taller rear tires and be prepared to adjust for speedo error.
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Lee
Dodge Dakota
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3/28/2008
10:05:12
| RE: Modifying O/D for better MPG's? Ideas?
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I have recently tried a trick that costs nothing up front and is guaranteed to produce way better mileage.
I slowed down! I accelerate slowly from stop lights, and (most importantly) I never go over 60 MPH unless I have to merge into traffic or avoid something. I just hang out in the right lane and cruise. So far, my mileage has improved dramatically. The engine just loafs along at 2,000 RPM instead of the 3,000 RPM at 80 MPH. I only drive 7 miles each way to work every day, so it doesn't take me any extra time to get there. In fact, I seem to get there quicker now! I also have no stress, as I don't care who passes me. I just watch the other cars try to burn as much gas as possible, only to meet up at the next red light together.
If you aren't in a giant hurry, try the above tip for some real fuel (and $$$) savings!
Lee
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NEP01
Dodge Dakota
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3/31/2008
19:57:33
|  RE: Modifying O/D for better MPG's? Ideas?
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What rear end gear ratio do you have now? If they are 3.93 or 4.10 you could go to a 3.55 and not loose much on the bottom and that would lower your cruising RPM significantly. Also, believe it or not, a few performance mods such as an SCT tuner or a few other options depending on what engine you have would help as long as you can keep your foot under control... I know thats the hard part! SCT tuning allows us to add timing down low which makes for better efficiency because you get more torque with means it takes less throttle to keep it moving.
Jason
www.neverenoughperformance.com
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Lee
Dodge Dakota
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4/01/2008
12:23:20
| RE: Modifying O/D for better MPG's? Ideas?
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Well, my "way better mileage" actually came out to be 1 MPG better - 14.5 MPG instead of 13.5 MPG. The truck has 90,000 miles on it, so I just changed the spark plugs (among other things). I will see what kind of mileage I get with the new plugs now. BTW, the O2 sensors are all original except for one of the post-cat ones that threw a code a couple of years ago. Would replacing the two pre-cat sensors help with the mileage? I have a smog check coming up in June, so I want the truck to run the best it can.
"What rear end gear ratio do you have now?"
I'm not sure who this question was directed at, but my truck has a 3.55 rear end. I did go to slightly larger tires than the truck came with, but I will likely drop back down to the original size when it's time to get new tires. Less rotating mass helps with performance and mileage.
Lee
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gen1dak
Dodge Dakota
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4/01/2008
12:57:38
| RE: Modifying O/D for better MPG's? Ideas?
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Usually anything after 60,000 miles on O2 sensors is a gift. Change 'em.
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Lee
Dodge Dakota
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4/01/2008
13:54:26
| RE: Modifying O/D for better MPG's? Ideas?
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"Usually anything after 60,000 miles on O2 sensors is a gift. Change 'em."
That's what I thought. When the post-cat sensor threw a code, I just bought a new one at Autozone for ~$70. Should I just do the same for the pre-cat ones, or do you recommend the dealer?
Lee
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NEP01
Dodge Dakota
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4/01/2008
20:30:18
| RE: Modifying O/D for better MPG's? Ideas?
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As long as its BOSCH it doesn't matter where it comes from in my opinion. I'm not sure about how O2 sensors act when they get old. If your really interested in seeing how your truck is running take it to a dyno and get a rundown of your Air/Fuel ratios at part throttle and light acceleration. It should hang around 14.7 A/F and maybe closer to 13.5 if you get into it a little. If you are interested in tuning, better mileage can be obtained using an SCT custom tuned flash device. When bottom end timing is added in the cruising areas of the map, efficiency is increased. You could even hook up some Innovate data logging equipment.
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gen1dak
Dodge Dakota
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4/02/2008
02:27:36
| RE: Modifying O/D for better MPG's? Ideas?
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Just say "NO!" to dealers unless you like getting shagged. Swap your out yourself. Remember to disconnect the battery while doing the work or if you have one of those little hand-held code readers, you can reset the computer that way. Either way, it's vital to reset the computer so it will recognize the new sensors.
O2 sensors stop working when they get old. There's a gradual fall-off in their performance, then they drop rapidly once they're mostly expended. What happens is, they cause the engine to run progressively richer. Once they konk out, the engine goes full rich. That's great at full throttle, but really sucks any other time.
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Lee
Dodge Dakota
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4/02/2008
10:15:37
| RE: Modifying O/D for better MPG's? Ideas?
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I will definitely do the job myself! It's not that hard, and I do have the code reader to reset the PCM. I found an article online that says to replace OBDII O2 sensors at 100,000 miles, so I will consider 90,000 miles to be close enough since it's a smog year for my registration.
Should I do just the pre-cat ones, or should I also do the post-cat one that I haven't replaced yet? I understand they are just there for monitoring the efficiency of the cats, but I can do it while I'm at it. If it wouldn't make any difference, I can save the $70+ for later...
Lee
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gen1dak
Dodge Dakota
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4/02/2008
10:57:50
| RE: Modifying O/D for better MPG's? Ideas?
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The post-cat unit will only be an issue when it throws a code and causes that annoying light. The pre-cats are the important ones as far as engine control. You can count on that post-cat unit going bad fairly soon, so it's a convenience vs cash issue, your call on that one. When OBDII was implemented, all the emissions stuff was supposed to last 100K, but time vs mileage...it all adds up. When they hit bottom, the truck will start dumping fuel and, at these prices, you'll have paid for them in wasted gas in no time. So 90K sounds like you got good use out of them.
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I hate cars
Dodge Dakota
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4/05/2008
22:33:20
| RE: Modifying O/D for better MPG's? Ideas?
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Just one ponderance. Why is it my wife's 5.2l ex cab dakota gets 15 if we're lucky, yet my ol mans 3/4 ton pickup with same engine gets 14 hooked to a car trailer loaded with a 3500 lb car?
Are V8 dakotas just designed that poorly?
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Kowalski
GenIII
4/06/2008
10:16:33
| RE: Modifying O/D for better MPG's? Ideas?
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Not at all. I'm very suspicious about the accuracy of your old man's milage claim. The only way I'd believe it is if it were taken from the overhead readout while the truck was going downhill.
Lead, follow, or get out of the way
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ewraven
Dodge Dakota
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4/06/2008
12:32:27
| RE: Modifying O/D for better MPG's? Ideas?
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Yeah, the overhead computer definately isn't very accurate. I sometimes wish that it didn't show MPG just for the very fact that it fools people so often.
Few will probably believe this, but recently on a trip, I averaged exactly 22.0 miles per gallon for the last 92.3 miles of the trip. Now of course, my average speed came out to be 50.80 miles per hour. But I was certainly impressed. lol
Every time I fill up with gas, I write down the miles and time from the overhead computer on the receipt and whip out the calculator and figure up the Real mpg right there.
The overhead computer is usually very innacurate.
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I hate cars
Dodge Dakota
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4/06/2008
23:29:43
| RE: Modifying O/D for better MPG's? Ideas?
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Proven mileage. He junks cars to supliment retirement, logged on 30,000 miles half of which are loaded. He only uses it to pull his trailer. Recently went to pick up a 66 coronet conv in NC and it got between 13 and 15 all the way back. including in the mountains. I used to own same truck myself as well. 318 mag 518OD 390 open rear diff. It just works...
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