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I posted this as an answer to another thread I started-occurs to me that some folks here are weight weenies-dropping weight is one of the few "mechanical" modifications that actually improves FE-so worth a posting.
Radiator blocks-engine block heaters and a few others also work-most commercial FEmodifications are scams ripoffs-CAI HEADERS EXHAUST MODS TURBINATORS H2 GENERATORS MAGNETS ON FUEL LINE 100 MPG CARBS- long list.

Some GM trucks-1990's came with both direct drive 13 3/4 lb
and or reduction drive 7 7/8 lb starters
6 lb weight loss-roughly .1% weight reduction
Supposed to be easier on battery-maybe so-sounds plausible-so motor off gliders might consider it-those owning 1/2 GMs.


A while back I posted asking if you can just put one of those tiny reduction drive starters in a 1998 Suburban 5.7 1500 2wd
if it originally came with a direct drive starter.
Through dumbness lack of knowledge cheapness brokeness trying to save a $$ ness
I ended up with TWO YES TWO "WRONG" starters.I had a direct drive ended up with two tiny reduction drive starters.
I found this out when I pulled mine and immediately noticed it was HUGE next to the new(and used) starters
Even worse the DD had a 9 tooth gear the RD had a 11 tooth gear.
I just put the old starter back in and hunted here-and other places for the answer.
Well the answer is GM used BOTH STARTERS in the same models same years!!??
Yeah it seemed odd to me, but that is it!
Not sure why- pretty sure it was for more than one year(1998)-so not as if they had to use up the old starters but maybe I am wrong about that.

Well back to can you switch.
Yes-direct bolt in.
But there was 2 curve balls.
1)My starter cable was TOO SHORT-ABOUT 1/2 inch too short.There was no way to just pull it very hard put eyelet over stud- and screw nut on-just couldn't do it-AND IT WOULD HAVE BEEN PRESSING ON A BRAKE LINE- bad idea all around.

I finally took off one of the hold down "cable directors" off-the 1st one you come to from the battery-holds cables to top of fame rail I think- Downside of this- biggish downside-it now is just 1/2-3/4 inch from the exhaust manifold.I won't leave it like this-hunting for a longer cable-maybe I will make one??What gauge is that wire-it is REALLY HEAVY-maybe 1.8" to 3/16" of multistrand copper wire- really really heavy! It is also heat insulated with aluminum "foil" and some sort of now
crunchy brittle insulation.

2) The old heat shield doesn't fit-too loose-so I left it off.This is also a big downside-the starter will fail early if it is getting cooked. I'll modify adapt the old shield soon- before the summer-Most of my trips are very short-6 miles-so no big deal until then-and I only drive maybe 60 miles/week.

So they do interchange-starts just fine-not chewing up the flywheel-
I did carefully look at the 9 and 11 tooth gears- tooth spacing exactly the same-about 8.5mm between points of teeth.
Did look at how far the gears would be from where they were mounted on both starters- exactly the same in both dimensions-the mounting depth and length is exactly the same.
Now the newer mini starters do seem to have slightly stouter mounting "holes" and the length of the mounting holes is slightly-about 1 thread- longer-so might be a good idea to use the very very slightly longer mounting bolts-1 thread longer.

Well that is it.
Probably better to just stick with whatever GM stuffed in there to begin with- but if you end up with a "ministarter" for some reason it will fit and work.
Weights
Direct Drive weighed 13 3/4 lbs
Reduction drive weighed 7 7/8 lbs
6 lbs heavier-almost twice as heavy.
The new starter does sound slightly different-just different-doesn't seem to spin the motor any faster or slower-
Luck
Charlie
PS THis should be at beginning-
They also claim to be easier on your battery-maybe so-sounds plausible.
I switched my DD to RD- not for weight loss-more because of a screw up(all mine)

Kudos on the weight loss! That alone pretty much makes it worth it. Can't say I understand how it's easier on the battery though. The starter's energy output (that is, the energy required to turn the engine over at the required RPM) would have to have a roughly commensurate energy input (the energy supplied by the battery for the starter to do its work). That is, of course, not counting internal losses due to any friction, better or worse efficiency of the motor windings, etc. But maybe someone could check my thought process on that?

On the battery you are right.No reason it would use less energy.
I THINK it is supposed to be more likely to turn the ICE when it is cold and there is less electrical energy available.So perhaps it is somewhat more likely to start when battery is dodgy.
Maybe that is where the "easier on battery" comes into play.
It is geared about 4/1 relative to the DD
It has 5/1 internal gearing and 11 tooth gear (What I've read)
The DD has a 9 tooth gear

I do like the lighter weight-free lunch in respect to FE and acceleration!!
You are right-No reason it would be "easier on battery" but might be better cold starting
I also am more confident in it-so more likely to shut it down at long redlights!
Charlie

I don't know about losing 6 pounds on a vehicle that weighs nearly 3 tons. (my 98 K1500 is almost 3 tons curb weight.) I think the weight difference is insignificant unless coupled with other weight loss strategies where you can add it up and take at least a few hundred pounds off the vehicle. Even at that, my K1500 only took a 2 MPG hit on the highway with a 700 pound Harley in the back. Assuming that its linear (it probably isn't exactly linear, but its probably close) you would have to shave about 350 pounds to gain 1 MPG (highway).

That all being said, I did change the starter in my 2000 GMC 1 ton cargo van, and it was the mini starter. VERY easy. I was shocked. My arms weren't tired holding it up while I started the bolts. As far as being easier on the battery I don't know. Electric motors are pretty efficient. I put the biggest alternators and batteries in my vehicles anyway, saves me worry when I'm in the middle of nowhere. I know it will start.

its possible that the motor has a higher efficiency since it spins faster and then its geared down.. so it may consume less amps.

How much do those cow magnets weigh? :)

08Escapehybrid
My Suburban is about 5200 lbs -pretty heavy.Trip weight 2 adults dog full tank loaded up-probably more like 6500 lbs-around town weight 5800 lbs
Now I have put it on a diet
1)Third row-78 lbs
2) single seat in second row- 59lbs
3)Starter-6lbs
Roughly 140 lbs-figure 140/5800= 2%
Hy mpg-pretty much independent of weight and I use high pressures(51psi) so probably not much change in RR- and I don't P&G hy-just set CC and DWL.
Weight loss won't help hy FE much at all-not the way I drive-might help P&Gers a bit.
City FE my crude guess is linear but not 1/1- just a guess but I would guess a 1% drop in weight is worth a 1/2% improvement in FE.
My 2% drop probably improves FE 1%- 20MPG becomes 20.2 mpg
The 6 lb starter savings would be .1% lighter- .05% better FE 20X 1.0005=20.01MPG
Ever little bit helps.
On most trucks 70 lbs should be worth about 0.1mpg city probably less HY but not too sure on that. I would guess you would need to drop 700 lbs to get 1 mpg better city.
Your K1500 A PICKUP?? Putting the HD in will increase the drag a bit-that could have been much of the drop in FE.The weight certainly would hurt FE- drag and weight

Herm-seems like I have seen the "easier on battery claim" so I repeated it. I can certainly see how it would start better with a marginal battery-cold weather etc.
If it is quicker starting it will use less energy
And maybe it is inherently slightly more efficient??
DD starters are obsolete according to Wikipedia-probably some good reason- weight being a good guess-

08- yes it was a heck of a lot easier installing the lighter starter-crawling under vehicle-arms all cramped up-grungy oily crap dropping in your face eyes-yes light was VERY good for install.

In any case it sure works better that the old worn out DD starter.
Anyone need a new RD starter?? Cheap $40-but shipping so much it is pointless-just get one off ebay-$60 delivered
Thanks,
Charlie

...Your K1500 A PICKUP?? Putting the HD in will increase the drag a bit-that could have been much of the drop in FE.The weight certainly would hurt FE- drag and weight...




Yes, my pickup is a 98 GMC K1500 extended cab with ~180,000 miles on it currently. Normally I have a fiberglass camper shell on it, so I'm dragging a huge air pocket behind me. With the HD in the back the camper shell was removed, so even though the bike created some turbulence, the air pocket should have been much smaller.

http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc1/10730_145067987293_612712293_2481448_5600921_n.jpg

http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash4/185870_10150091333017294_612712293_5987361_991075_n.jpg

Wow- it is in nice shape for 14 years old.
Heck you are in a "almost rust bucket state,right"
Do they salt your roads??
My Suburban-amazing how much your capped pickup looks like a Suburban- has nice paint- but PO had a few small dents.
GM did seem to have their paint problems sorted out by the late 90's. Some late 80's early 90's GMs have those HUGE patches of no paint rust on the hoods roofs etc.

How do you keep it looking like that??
Charlie
PS The HD does sit pretty low in the bed-not too much above roofline.

Actually, they do a lot of pretreating the roads with some sort of liquid chemical before the snow & ice starts. It dries on the road, and will last a couple of weeks until activated by snow/ice, or its washed off by rain. Not sure what they put down though. In an actual snow event, they do heavily salt. There is one rust spot starting, its on the driver side rocker panel, I plan to sand it down, prime & paint it when I have a day that I've got nothing better to do. Other than that, the rear bumper is rusted through. Now that its not a daily driver anymore, I'm kinda hesitant to spend $ to replace the bumper. Besides, the driver's side door is still bashed in from where someone hit & run on me in a parking lot last winter. Maybe if I ran into a junkyard bumper and door in nice shape cheap, I'd consider it. The truck was 5 or 6 years old when I bought it, and truth be told, I rarely wash it, and have never waxed it aside from the spray waxes that might be applied in automatic car washes. When they do salt the roads I take it through an automatic wash the next week and get the everything wash with undercarriage blast.

Here's a pic of the damage they did:

http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc4/164569_472893112293_612712293_5611646_1010255_n.jpg

If it is quicker starting it will use less energy
And maybe it is inherently slightly more efficient??
DD starters are obsolete according to Wikipedia-probably some good reason- weight being a good guess-


The claim that a faster spinning starter starts faster sounds familiar.. is it cranking over faster?.

One day cars will open all the valves to remove compression prior to cranking over.

To develop torque on a direct drive motor you either need: large diameter or heavier currents for more intense magnetic fields by increasing the amps.. large diameter could mean weight, higher currents is limited by the battery so the alternative is the same as Honda does with their engines.. rev the heck out of them and then gear down to increase the torque. The smaller motor probably consumes less valuable copper also.

High currents induce heavy IR losses in the cables and windings also. The thin pancake motors used by Honda and Hyundai hybrids are an example of increasing torque in a direct drive by increasing the diameter of the motor.

The smaller motor probably consumes less valuable copper also.
.
Definitely less valuable copper, and less valuable iron, too, in the motor itself. That cost savings has to be balanced against the cost of reduction gearing, though. If the smaller starter cranks the same engine at the same speed, I doubt there'd be much difference in current draw.

I did some research on this, they also saved money by reducing the gage of wire to the battery needed by the lower currents of the geared starter.

08- Yeah hit and leave in parking lots is standard procedure here. I either park waaaay far from the store or try to find really nice cars to park next to.
Still get door dings!

Herm- it certainly spins it better in cold weather- and I haven't had any of the "barely turn over" episodes.
To its credit when it was working well the DD starter would spin that 350 very fast!
Not sure the RD actually spins the motor faster when both working well-the ICE starts sooo quickly-reaction time really- it is hard to say.
The RD does "sound different"

These modern ICE start so quickly I wouldn't be surprised to find out GM went for a lower peak ICE spin rate(which probably would use a tiny bit less energy save battery etc) with the RD starter.

On a nice warm day-warm oil-with both starters working correctly-I might bet the DD spins the ICE slightly quicker.
Now on a cold day-the RD sure seems to win.

Herm- my DD starter(now RD) sure seems to have a a big gauge wire- looks like 3/16" maybe 1/4" of copper wires.
Charlie

Yes, my pickup is a 98 GMC K1500 extended cab with ~180,000 miles on it currently. Normally I have a fiberglass camper shell on it, so I'm dragging a huge air pocket behind me. With the HD in the back the camper shell was removed, so even though the bike created some turbulence, the air pocket should have been much smaller.

http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc1/10730_145067987293_612712293_2481448_5600921_n.jpg

http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash4/185870_10150091333017294_612712293_5987361_991075_n.jpg

I havent noticed an mpg difference since I put the cap on my truck. Used to run a bed cover. There might be a mpg difference, but I havent seen it yet.

I had a cap on my 2001 V-8 Tundra.
It was one of those that tapered UPWARD as it went back so you could put a pretty tall item
back there(we actually slept in it on trips-rode back there also- bad idea dangerous)

I never got good mpg out of the Tundra-cap or no cap.
Now I didn't P&G in the city- just egg under foot old style driving-don't think I ever got better the 14mpg on city tanks.

Same story hy- but I can compare it to the Suburban because I used the CC and kept it under 60 mph while commuting in 2002 2003 during the fuel runup 2nd iraq war.
It very very occasionally got 18mpg- barely 18mpg.
Now I'm better hypermiling now- but the Suburban will get 22mpg or better driven same way-despite 5.7 vs 4.7 5200 lbs vs 4400 lbs- maybe driving technique would have gotten me 20 mpg- but I would have never guessed a fairly primitive 2 valve pushrod V-8 would beat a modern smaller 4 valve Toyota engine-GM apparently knows something about inherent engine efficiency and efficient CC burning.
Still surprised at the Little Tundra losing to the Suburban.Maybe it was technique- but I was
driving to save fuel back then- stunned it cost me $9/day to get to work($1.69 gas- it had been $1.25 just a few months before-this was a HUGE jump to us back then-we forgot about 1979)

Charlie

Several years ago I had become skilled enough to get the K1500 to pull 16-17 MPG city, but I gave up after a few months. I was shutting the engine down at lights, accelerating under load, and downshifting to force DFCO when approaching red lights.

After a few months of this strategy, I had noticed a vibrating sensation in the accelerator pedal. When I took it in for service it turned out to be the beginning stages of torque converter failure. I have no idea if the tc was getting ready to fail anyway as it had roughly 150,000 miles on it at the time, or did my newly adopted driving style cause the failure. Luckily, all I needed was a new TC, and then I had it flushed & filled with synthetic ATF, and it has been trouble free ever since. I have decided that really aggressive hypermiling is not something to be done on a high mileage automatic, and I've let it go back to getting 13 MPG city.

All I do is motor on P&G-and 50-52psi tires.
I never tried motor off gliding-not with a dodgy starter and 217,000 mile drivetrain(AT rebuilt at 185,000- but everything else original).

I average about 15mpg on my 5-6 mile-one way- trips to the various schools I sub teach at.
Usually 14mpg (6:30 am) 16 mpg(2:45 pm)-in winter maybe 16mpg both ways in summer(despite AC blasting). There are only 2 redlights-4 stop signs-on the usual route (3 of the schools are more or less same route-fairly light traffic).
Unfortunately my wife drives the Suburban when son has Prius-most of the time-and trips kill mpg- no gliding.
My tanks are 12.5-13mpg - wife puts maybe 15 miles per week-I put 50.
Roughly same mpg you get despite the 2wd vs 4x4.
I'm not up for shutting the motor off-too tricky-besides this vehicle has to last another 16 months without any significant repair costs.It is surprisingly reliable- but 218,000 miles is 218,000 miles!!
When I become more flush-20 months or so-gas prices will be waaay up-Suburban prices will be waaaay down-I'll be able to sell it for $1500(maybe) but buy a reasonably low mile(100,000+) 2004 for maybe as little as $5000-get better FE(14/18 vs 12/17) 6 years less wear tear and much better brakes(OEM brakes on this model are marginal).
Charlie

I never did much with motor off gliding, as the ATF is not circulating with the engine off, so the parts are starving for oil. Many years ago, I did an experiment in the middle of summer. One tank I drove with the a/c off and windows up (vent fan on high). The next tank I did with that A/C on max for the entire tank. Both tanks were within 1/2 MPG, so the difference was statistically insignificant. Since then, I decided if I needed a/c I'd just turn it on. I think the reason that it doesn't effect the FE is because the compressor takes such a small fraction of a 350's output, that the motor really doesn't notice that its even on.

Good to know- too hot in NOLA to run with no AC.
Thanks
Charlie

Well, I don't have a/c at work, so I am able to tolerate more heat than most others.