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Old 01-11-2019, 05:13 AM   #11 (permalink)
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Originally Posted by rmay635703 View Post
https://ecomodder.com/forum/showthre...mpg-33961.html

Read the above

You will have better luck with that approach
Interesting read. Thanks.

I wish someone would have done a Big Chevy van.

Thanks.

Rich

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Old 01-11-2019, 05:15 AM   #12 (permalink)
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Originally Posted by Frank Lee View Post
One can overdo it with gear meshes (lossy drivetrain) and too high gearing (can't pull it unless going downhill) or maybe can pull it empty but still too low rpms- out of the BSFC sweet spot.
I have considered this and feel one more OD will not make that happen, but it is a concern.

Rich
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Old 01-11-2019, 05:30 AM   #13 (permalink)
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Originally Posted by oil pan 4 View Post
If you slow the engine down too much you fall out of its efficiency range. Even worse yet, combustion and crank shafts harmonics tear up the rod bearings.

Figure out the lowest recommend cruise rpm and gear for that.
Pushing the operating range down to say 1,000 rpm is just going to ruin the engine.
I have considered that. My plan are for our highway speeds of 80MPH.

These are both low RPM motors, the Ford 4.6 comes with a factory Ford version of the 85/90 Chevy Tune port injection system with the extra that it has a Sequential injection system which has the better use of fuel and may get great MPG, VS the Chevy batch injection system... On the other hand I can get a special add on board to allow a lean burn cruse customize to its best setting for the Van.

Both motors are low RPM motors, both are unable to run faster than 5500 RPMs and both are past their power peek curve (4500) at those points.

Both have lockup Torque convertors.

Both motors seem to have plenty of torque at around 1000 RPMs with my target range of around 1500 RPMs.

From all I have read and tested I really think this will work.

Thanks for your input.

Rich

Last edited by racprops; 01-11-2019 at 10:26 AM..
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Old 01-11-2019, 09:49 AM   #14 (permalink)
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Here is some interesting info on the idea of a second OD on OD automatics.

Ford Auxiliary Overdrive unit for Automatic Transmissions | Gear Vendor Overdrive - Drivetrain

The three lesser features to this conversions, First is that Gear Venders is only a 22% overdrive, the Borg Warner is a 72% over drive.

Second it the $3000.00 price.

Third there has been some questions to it durability.

Rich
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Old 01-11-2019, 10:11 AM   #15 (permalink)
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There are 5 and 6 speed transmissions that have very wide gear spread already. The modified NV4500 I have in my Suburban has the following ratios: 5.61-3.04-1.67-1.00-0.643 which is a 8.72 gear spread.

With 4.10's first is unnecessary for a torque down low engine, so I take off in second. Thus the vehicle could support a much taller rear end ratio and still take off fine in first, to the point that the overdrive ratio could be pushed to the limit of the engine's torque curve versus road load. For example, with 235/85R16 tires and relatively common 3.42 gears I would be turning 1208 rpm at 55 MPH. All with only one transmission and no auxiliary devices. With 3.08 gears this would be 1088 RPM. This is probably beyond the reasonably limit of most engines without drag and weight reduction to reduce the road load.

For 2wd applications there is the Tremec 6060 with 2.97 first and 0.50 overdrive. Less gear spread but more intermediate gears.

So given there are existing single transmissions with such spreads, I don't see the point in using multiple boxes outside of specialized use cases (e.g. rock crawling).
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Old 01-11-2019, 10:37 AM   #16 (permalink)
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Originally Posted by aardvarcus View Post
There are 5 and 6 speed transmissions that have very wide gear spread already. The modified NV4500 I have in my Suburban has the following ratios: 5.61-3.04-1.67-1.00-0.643 which is a 8.72 gear spread.

With 4.10's first is unnecessary for a torque down low engine, so I take off in second. Thus the vehicle could support a much taller rear end ratio and still take off fine in first, to the point that the overdrive ratio could be pushed to the limit of the engine's torque curve versus road load. For example, with 235/85R16 tires and relatively common 3.42 gears I would be turning 1208 rpm at 55 MPH. All with only one transmission and no auxiliary devices. With 3.08 gears this would be 1088 RPM. This is probably beyond the reasonably limit of most engines without drag and weight reduction to reduce the road load.

For 2wd applications there is the Tremec 6060 with 2.97 first and 0.50 overdrive. Less gear spread but more intermediate gears.

So given there are existing single transmissions with such spreads, I don't see the point in using multiple boxes outside of specialized use cases (e.g. rock crawling).
My problem is I am very happy with both the Ford and Chevy power.

The part I am NOT happy with is the gas millage, 23MPG highway for the Ford and 14MPG highway for the Van.

The Ford is all set up and other than a few minor improvements I do not expect to find big MPG improvements in it.

The Chevy needs a better injection system and PCM changes.

Your talking about transmissions I cannot use in either of my cars. If I did they would cost a lot to convert. As much as my idea to convert to the 6 speeds and 8 speed transmissions.

The idea of adding a over drive seems like the lowest cost and biggest change for better MPG.

It stops my search for those rare low ratio rear end gears, same search for those 6/8 speeds transmissions and fittings, and saves the costs of rebuilding the two rear ends, the costs of shifter and computer controls for those new transmissions.

All I need do is mount the B&W over drive to the transmissions, it is cable and electrically controlled, simple to set up and use.

With the van I also think the gear splitting will help find a best fit of power-RPMs-speed in hill climes.

Rich

Last edited by racprops; 01-11-2019 at 10:42 AM..
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Old 01-11-2019, 01:11 PM   #17 (permalink)
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I was talking specifically about your Chevy van, I don't have much experience with ford engines/transmissions. Both transmissions I mentioned will bolt right up to any engine offered in a 1993 Chevy conversion van. The 1991 K2500 Chevy with 5.7/350 TBI I converted from a 4l60 to a NV4500 cost me about $1000 total to convert, used transmission new clutch/flywheel.

It would be drastically less work to put in a period appropriate transmission into that van (like a NV4500) than to try to bolt two transmission together or to hook up an auxiliary overdrive unit. It would be way easier than some new exotic 6 or 8 speed auto. I have converted two 90s model Chevy's from auto to stick, a pickup and a Suburban with a 4l60 and 4l80e respectively. I am sure your Chevy van has one of those transmissions. The correct sensors just bolt right up, everything works fine.

If you want a more complicated project a Tremec 6060 should bolt up to the engine but may require some other custom work to fit.
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Old 01-11-2019, 06:26 PM   #18 (permalink)
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Quote:
Originally Posted by aardvarcus View Post
I was talking specifically about your Chevy van, I don't have much experience with ford engines/transmissions. Both transmissions I mentioned will bolt right up to any engine offered in a 1993 Chevy conversion van. The 1991 K2500 Chevy with 5.7/350 TBI I converted from a 4l60 to a NV4500 cost me about $1000 total to convert, used transmission new clutch/flywheel.

It would be drastically less work to put in a period appropriate transmission into that van (like a NV4500) than to try to bolt two transmission together or to hook up an auxiliary overdrive unit. It would be way easier than some new exotic 6 or 8 speed auto. I have converted two 90s model Chevy's from auto to stick, a pickup and a Suburban with a 4l60 and 4l80e respectively. I am sure your Chevy van has one of those transmissions. The correct sensors just bolt right up, everything works fine.

If you want a more complicated project a Tremec 6060 should bolt up to the engine but may require some other custom work to fit.

The THING is I do not want a stick shift. I much perfir automatics.

On a long trip coming into a city and having to drive, look for directions, find the hotel is all I want to handle, having to work a clutch and shift is too much.

As a teenager I switched a 56 Studebaker Golden Hawk from an auto to a 3 speed with overdrive. My next car was a 68 Mercury Cougar XR7 with a 4 speed. My Ecnoline Van had a 3 on the Tree.

We have VW Bug with its 4 speed and we had a 86 626 with a 5 speed.

I have driven enough Sticks to know them and myself well.

For fun give me a stick.

For work car or truck (van) give me a auto.

Rich
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Old 01-11-2019, 07:18 PM   #19 (permalink)
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The slowest I have seen a tall geared V8 chug along is 70mph at just shy of 1,600rpm.
Just make sure what speed you run at makes good oil pressure.
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Old 01-11-2019, 11:36 PM   #20 (permalink)
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Quote:
Originally Posted by racprops View Post
The THING is I do not want a stick shift. I much perfir automatics.

Rich
Your preference will cost $$$

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