ACCURATE SPEEDOMETER?

Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
gearing, and D30 front/35 rear. I recently upgraded my tires from the
stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
for a reliable way to tell if my speedometer is off at all with the
tire upgrade. I do not have access to a GPS system. What I HAVE done
is to use the tripometer (with tenths), and hold steady at 60 mph (my
speedometer said 60) for one mile while watching my clock. I am
EXTREMELY close to going 1 mile in 1 minute by using this method. Is
this reliable to tell whether or not my speedometer is dead on? I
have NOT changed the speedometer gear yet, or had the computer changed
to reflect the larger sized tires. Also, I am not using my OD (6th)
much on the highway, but when I get up to 65 (the speedometer says
65), I am running at about 2500 rpms in 5th. Is this bad, or should I
be shifting into the OD (6th)? I do fine with 1st through 5th. Just
not sure what speed or what rpms I should be using 6th. Any help is
really appreciated.

On Mon, 17 Sep 2007 08:38:45 -0500, c > wrote:

>Tracie wrote:
>> Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
>> gearing, and D30 front/35 rear. I recently upgraded my tires from the
>> stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
>> for a reliable way to tell if my speedometer is off at all with the
>> tire upgrade. I do not have access to a GPS system. What I HAVE done
>> is to use the tripometer (with tenths), and hold steady at 60 mph (my
>> speedometer said 60) for one mile while watching my clock. I am
>> EXTREMELY close to going 1 mile in 1 minute by using this method. Is
>> this reliable to tell whether or not my speedometer is dead on? I
>> have NOT changed the speedometer gear yet, or had the computer changed
>> to reflect the larger sized tires. Also, I am not using my OD (6th)
>> much on the highway, but when I get up to 65 (the speedometer says
>> 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
>> be shifting into the OD (6th)? I do fine with 1st through 5th. Just
>> not sure what speed or what rpms I should be using 6th. Any help is
>> really appreciated.
>>
>
>The trip odometer should be close. You can also use the mile markers on
>the side of the highways assuming those are correct in your area. I was
>told by a local road worker in Wisconsin that they are very accurate,
>but that may vary by states.
>
>As far as 6th gear is concerned, using only 5th gear will cause more
>engine wear, but it may or may not hurt fuel economy. The only thing to
>do there is to test it out. I would think that with the small increase
>in tire diameter, you should still be using 6th gear. You do have a very
>high gear in your axles, so it is probably worth testing.
>
>Chris


Your speedo with be off a good bit. You will be going faster than it
records. With 65 indicated you will be doing about 73 MPH. With 3.07
gear it has got to be a bit of a slug at times too with 31's. Below is
a link where you can run some numbers yourself

http://www.snoman.com/HTML/axlecalc_5a.html
-----------------
TheSnoMan.com

Your watch is a bit clunky, but the method is correct.

A stop watch works better. Ignore the odometer, and measure your miles with
the mile markers along the shoulder of all federal and most state highways.
Divide the time in seconds that it takes to travel a measured mile into
3600, the result will be your speed.

Set the Cruise Control at 60. Measure the time it takes to go a mile. Divide
3600 by the time. 3600 / 60 =- 60. 3600 / 52 = 70. 3600 / 45 = 80.




"Tracie" > wrote in message
ups.com...
> Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
> gearing, and D30 front/35 rear. I recently upgraded my tires from the
> stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
> for a reliable way to tell if my speedometer is off at all with the
> tire upgrade. I do not have access to a GPS system. What I HAVE done
> is to use the tripometer (with tenths), and hold steady at 60 mph (my
> speedometer said 60) for one mile while watching my clock. I am
> EXTREMELY close to going 1 mile in 1 minute by using this method. Is
> this reliable to tell whether or not my speedometer is dead on? I
> have NOT changed the speedometer gear yet, or had the computer changed
> to reflect the larger sized tires. Also, I am not using my OD (6th)
> much on the highway, but when I get up to 65 (the speedometer says
> 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
> be shifting into the OD (6th)? I do fine with 1st through 5th. Just
> not sure what speed or what rpms I should be using 6th. Any help is
> really appreciated.
>

On Mon, 17 Sep 2007 08:38:45 -0500, c > wrote:

>As far as 6th gear is concerned, using only 5th gear will cause more
>engine wear


On a foot note, I do not know were this myth started. The engine is
not going to wear out any sooner in 5th and may actually last longer
if 6th is so tall that engine lugs. A few extra RPM never hurt any
engine and lower RPM lugging is potentailly far more damaging and
tough on bearings.
-----------------
TheSnoMan.com

Tracie wrote:
> Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
> gearing, and D30 front/35 rear. I recently upgraded my tires from the
> stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
> for a reliable way to tell if my speedometer is off at all with the
> tire upgrade. I do not have access to a GPS system. What I HAVE done
> is to use the tripometer (with tenths), and hold steady at 60 mph (my
> speedometer said 60) for one mile while watching my clock. I am
> EXTREMELY close to going 1 mile in 1 minute by using this method. Is
> this reliable to tell whether or not my speedometer is dead on? I
> have NOT changed the speedometer gear yet, or had the computer changed
> to reflect the larger sized tires. Also, I am not using my OD (6th)
> much on the highway, but when I get up to 65 (the speedometer says
> 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
> be shifting into the OD (6th)? I do fine with 1st through 5th. Just
> not sure what speed or what rpms I should be using 6th. Any help is
> really appreciated.
>

The (ones that have posed here) older TJ speedometers became correct
when 31" tire were put on.

Your mile per minute is a good base to tell it is close.

The only other way is to find a measured mile or a friend with a GPS or
even ask a cop to pace you because 'you just got new tires and don't
want to break the law'. Only a cop's speedometer would be reliable for
this, cars can be off too according to tire size.

I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
highway which I get with my 4th gear. (have 33's and 3.31 gears) That
rpm gives me good throttle control and prevents engine lugging. I also
get a pretty stable 11L/100km or 23 mpg running there.

If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
which makes for the need of the full gas pedal travel to adjust speed or
hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
my gas mileage by at least 5-8 mpg.

You can find out easy. Just compare gas mileages when using only 5th on
the highway and when using 6th mostly. I have one trip I do lots to get
bush camping which is 201 km from gas station to gas station so I have
an easy check point.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

On Sep 17, 11:17 am, Mike Romain > wrote:
> Tracie wrote:
> > Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
> > gearing, and D30 front/35 rear. I recently upgraded my tires from the
> > stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
> > for a reliable way to tell if my speedometer is off at all with the
> > tire upgrade. I do not have access to a GPS system. What I HAVE done
> > is to use the tripometer (with tenths), and hold steady at 60 mph (my
> > speedometer said 60) for one mile while watching my clock. I am
> > EXTREMELY close to going 1 mile in 1 minute by using this method. Is
> > this reliable to tell whether or not my speedometer is dead on? I
> > have NOT changed the speedometer gear yet, or had the computer changed
> > to reflect the larger sized tires. Also, I am not using my OD (6th)
> > much on the highway, but when I get up to 65 (the speedometer says
> > 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
> > be shifting into the OD (6th)? I do fine with 1st through 5th. Just
> > not sure what speed or what rpms I should be using 6th. Any help is
> > really appreciated.
>
> The (ones that have posed here) older TJ speedometers became correct
> when 31" tire were put on.
>
> Your mile per minute is a good base to tell it is close.
>
> The only other way is to find a measured mile or a friend with a GPS or
> even ask a cop to pace you because 'you just got new tires and don't
> want to break the law'. Only a cop's speedometer would be reliable for
> this, cars can be off too according to tire size.
>
> I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
> highway which I get with my 4th gear. (have 33's and 3.31 gears) That
> rpm gives me good throttle control and prevents engine lugging. I also
> get a pretty stable 11L/100km or 23 mpg running there.
>
> If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
> which makes for the need of the full gas pedal travel to adjust speed or
> hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
> my gas mileage by at least 5-8 mpg.
>
> You can find out easy. Just compare gas mileages when using only 5th on
> the highway and when using 6th mostly. I have one trip I do lots to get
> bush camping which is 201 km from gas station to gas station so I have
> an easy check point.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's - Gone to the rust pile...
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590
> (More Off Road album links at bottom of the view page)- Hide quoted text -
>
> - Show quoted text -

So, assuming that my speedometer is correct, running approximately
2500 rpms in 5th gear at 65 mph will NOT hurt my engine or cause
increased engine wear? If I were to shift into OD (6th), what is the
approximate rpms that I should be running so as to not cause lugging
or increased engine wear?

THANKS

On Sep 17, 11:26 am, Tracie > wrote:
> On Sep 17, 11:17 am, Mike Romain > wrote:
>
>
>
>
>
> > Tracie wrote:
> > > Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
> > > gearing, and D30 front/35 rear. I recently upgraded my tires from the
> > > stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
> > > for a reliable way to tell if my speedometer is off at all with the
> > > tire upgrade. I do not have access to a GPS system. What I HAVE done
> > > is to use the tripometer (with tenths), and hold steady at 60 mph (my
> > > speedometer said 60) for one mile while watching my clock. I am
> > > EXTREMELY close to going 1 mile in 1 minute by using this method. Is
> > > this reliable to tell whether or not my speedometer is dead on? I
> > > have NOT changed the speedometer gear yet, or had the computer changed
> > > to reflect the larger sized tires. Also, I am not using my OD (6th)
> > > much on the highway, but when I get up to 65 (the speedometer says
> > > 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
> > > be shifting into the OD (6th)? I do fine with 1st through 5th. Just
> > > not sure what speed or what rpms I should be using 6th. Any help is
> > > really appreciated.
>
> > The (ones that have posed here) older TJ speedometers became correct
> > when 31" tire were put on.
>
> > Your mile per minute is a good base to tell it is close.
>
> > The only other way is to find a measured mile or a friend with a GPS or
> > even ask a cop to pace you because 'you just got new tires and don't
> > want to break the law'. Only a cop's speedometer would be reliable for
> > this, cars can be off too according to tire size.
>
> > I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
> > highway which I get with my 4th gear. (have 33's and 3.31 gears) That
> > rpm gives me good throttle control and prevents engine lugging. I also
> > get a pretty stable 11L/100km or 23 mpg running there.
>
> > If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
> > which makes for the need of the full gas pedal travel to adjust speed or
> > hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
> > my gas mileage by at least 5-8 mpg.
>
> > You can find out easy. Just compare gas mileages when using only 5th on
> > the highway and when using 6th mostly. I have one trip I do lots to get
> > bush camping which is 201 km from gas station to gas station so I have
> > an easy check point.
>
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's - Gone to the rust pile...
> > Canadian Off Road Trips Photos: Non members can still view!
> > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590
> > (More Off Road album links at bottom of the view page)- Hide quoted text -
>
> > - Show quoted text -
>
> So, assuming that my speedometer is correct, running approximately
> 2500 rpms in 5th gear at 65 mph will NOT hurt my engine or cause
> increased engine wear? If I were to shift into OD (6th), what is the
> approximate rpms that I should be running so as to not cause lugging
> or increased engine wear?
>
> THANKS- Hide quoted text -
>
> - Show quoted text -

Oh, nevermind. I think I just answered my own question. : D

I am assuming that the approximate 2500 rpms would apply to the OD
(6th) gear as well to prevent increased engine wear and lugging?

On Sep 17, 11:34 am, Tracie > wrote:
> On Sep 17, 11:26 am, Tracie > wrote:
>
>
>
>
>
> > On Sep 17, 11:17 am, Mike Romain > wrote:
>
> > > Tracie wrote:
> > > > Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
> > > > gearing, and D30 front/35 rear. I recently upgraded my tires from the
> > > > stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
> > > > for a reliable way to tell if my speedometer is off at all with the
> > > > tire upgrade. I do not have access to a GPS system. What I HAVE done
> > > > is to use the tripometer (with tenths), and hold steady at 60 mph (my
> > > > speedometer said 60) for one mile while watching my clock. I am
> > > > EXTREMELY close to going 1 mile in 1 minute by using this method. Is
> > > > this reliable to tell whether or not my speedometer is dead on? I
> > > > have NOT changed the speedometer gear yet, or had the computer changed
> > > > to reflect the larger sized tires. Also, I am not using my OD (6th)
> > > > much on the highway, but when I get up to 65 (the speedometer says
> > > > 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
> > > > be shifting into the OD (6th)? I do fine with 1st through 5th. Just
> > > > not sure what speed or what rpms I should be using 6th. Any help is
> > > > really appreciated.
>
> > > The (ones that have posed here) older TJ speedometers became correct
> > > when 31" tire were put on.
>
> > > Your mile per minute is a good base to tell it is close.
>
> > > The only other way is to find a measured mile or a friend with a GPS or
> > > even ask a cop to pace you because 'you just got new tires and don't
> > > want to break the law'. Only a cop's speedometer would be reliable for
> > > this, cars can be off too according to tire size.
>
> > > I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
> > > highway which I get with my 4th gear. (have 33's and 3.31 gears) That
> > > rpm gives me good throttle control and prevents engine lugging. I also
> > > get a pretty stable 11L/100km or 23 mpg running there.
>
> > > If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
> > > which makes for the need of the full gas pedal travel to adjust speed or
> > > hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
> > > my gas mileage by at least 5-8 mpg.
>
> > > You can find out easy. Just compare gas mileages when using only 5th on
> > > the highway and when using 6th mostly. I have one trip I do lots to get
> > > bush camping which is 201 km from gas station to gas station so I have
> > > an easy check point.
>
> > > Mike
> > > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > > 88 Cherokee 235 BFG AT's - Gone to the rust pile...
> > > Canadian Off Road Trips Photos: Non members can still view!
> > > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590
> > > (More Off Road album links at bottom of the view page)- Hide quoted text -
>
> > > - Show quoted text -
>
> > So, assuming that my speedometer is correct, running approximately
> > 2500 rpms in 5th gear at 65 mph will NOT hurt my engine or cause
> > increased engine wear? If I were to shift into OD (6th), what is the
> > approximate rpms that I should be running so as to not cause lugging
> > or increased engine wear?
>
> > THANKS- Hide quoted text -
>
> > - Show quoted text -
>
> Oh, nevermind. I think I just answered my own question. : D
>
> I am assuming that the approximate 2500 rpms would apply to the OD
> (6th) gear as well to prevent increased engine wear and lugging?- Hide quoted text -
>
> - Show quoted text -

Which would probably be somewhere in the neighborhood of 70-75 mph in
6th at approximately 2500 rpms.

Tracie wrote:
> On Sep 17, 11:17 am, Mike Romain > wrote:
>
>>Tracie wrote:
>>
>>>Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
>>>gearing, and D30 front/35 rear. I recently upgraded my tires from the
>>>stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
>>>for a reliable way to tell if my speedometer is off at all with the
>>>tire upgrade. I do not have access to a GPS system. What I HAVE done
>>>is to use the tripometer (with tenths), and hold steady at 60 mph (my
>>>speedometer said 60) for one mile while watching my clock. I am
>>>EXTREMELY close to going 1 mile in 1 minute by using this method. Is
>>>this reliable to tell whether or not my speedometer is dead on? I
>>>have NOT changed the speedometer gear yet, or had the computer changed
>>>to reflect the larger sized tires. Also, I am not using my OD (6th)
>>>much on the highway, but when I get up to 65 (the speedometer says
>>>65), I am running at about 2500 rpms in 5th. Is this bad, or should I
>>>be shifting into the OD (6th)? I do fine with 1st through 5th. Just
>>>not sure what speed or what rpms I should be using 6th. Any help is
>>>really appreciated.
>>
>>The (ones that have posed here) older TJ speedometers became correct
>>when 31" tire were put on.
>>
>>Your mile per minute is a good base to tell it is close.
>>
>>The only other way is to find a measured mile or a friend with a GPS or
>>even ask a cop to pace you because 'you just got new tires and don't
>>want to break the law'. Only a cop's speedometer would be reliable for
>>this, cars can be off too according to tire size.
>>
>>I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
>>highway which I get with my 4th gear. (have 33's and 3.31 gears) That
>>rpm gives me good throttle control and prevents engine lugging. I also
>>get a pretty stable 11L/100km or 23 mpg running there.
>>
>>If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
>>which makes for the need of the full gas pedal travel to adjust speed or
>>hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
>>my gas mileage by at least 5-8 mpg.
>>
>>You can find out easy. Just compare gas mileages when using only 5th on
>>the highway and when using 6th mostly. I have one trip I do lots to get
>>bush camping which is 201 km from gas station to gas station so I have
>>an easy check point.
>>
>>Mike
>>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>>88 Cherokee 235 BFG AT's - Gone to the rust pile...
>>Canadian Off Road Trips Photos: Non members can still view!
>>Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590
>>(More Off Road album links at bottom of the view page)- Hide quoted text -
>>
>>- Show quoted text -
>
>
> So, assuming that my speedometer is correct, running approximately
> 2500 rpms in 5th gear at 65 mph will NOT hurt my engine or cause
> increased engine wear? If I were to shift into OD (6th), what is the
> approximate rpms that I should be running so as to not cause lugging
> or increased engine wear?
>
> THANKS
>

Your minimal tire size increase likely made your speedo/odo more
accurate as they tend to read high from the manufacturer. That way
warranties expire sooner and manufacturers save money. I'd bet you are
very close now. For fuel economy, use the highest gear you can while
staying in the power band (not lugging). Lugging will become immediately
apparent and you do it by feel, not by someone telling you what RPM to
run. If you shift into too high a gear, you will notice a power response
loss and ultimately your engine will lug. Downshift.

tw

Tracie wrote:
> On Sep 17, 11:17 am, Mike Romain > wrote:
>> Tracie wrote:
>>> Hello all. I have a 2006 Wrangler X with 6 speed manual tranny, 3.07
>>> gearing, and D30 front/35 rear. I recently upgraded my tires from the
>>> stock 215/75/15 to 31/10.5/15 BFG All Terrain T/A KO. I am looking
>>> for a reliable way to tell if my speedometer is off at all with the
>>> tire upgrade. I do not have access to a GPS system. What I HAVE done
>>> is to use the tripometer (with tenths), and hold steady at 60 mph (my
>>> speedometer said 60) for one mile while watching my clock. I am
>>> EXTREMELY close to going 1 mile in 1 minute by using this method. Is
>>> this reliable to tell whether or not my speedometer is dead on? I
>>> have NOT changed the speedometer gear yet, or had the computer changed
>>> to reflect the larger sized tires. Also, I am not using my OD (6th)
>>> much on the highway, but when I get up to 65 (the speedometer says
>>> 65), I am running at about 2500 rpms in 5th. Is this bad, or should I
>>> be shifting into the OD (6th)? I do fine with 1st through 5th. Just
>>> not sure what speed or what rpms I should be using 6th. Any help is
>>> really appreciated.
>> The (ones that have posed here) older TJ speedometers became correct
>> when 31" tire were put on.
>>
>> Your mile per minute is a good base to tell it is close.
>>
>> The only other way is to find a measured mile or a friend with a GPS or
>> even ask a cop to pace you because 'you just got new tires and don't
>> want to break the law'. Only a cop's speedometer would be reliable for
>> this, cars can be off too according to tire size.
>>
>> I find 'my' engine 'much' prefers to be running at 2300-2500 rpm on the
>> highway which I get with my 4th gear. (have 33's and 3.31 gears) That
>> rpm gives me good throttle control and prevents engine lugging. I also
>> get a pretty stable 11L/100km or 23 mpg running there.
>>
>> If I go to overdrive or 5th gear, the rpm drops to 1750 or so at 65 mph
>> which makes for the need of the full gas pedal travel to adjust speed or
>> hold a hill or wind vs a twitch of the pedal in 4th. This low rpm drops
>> my gas mileage by at least 5-8 mpg.
>>
>> You can find out easy. Just compare gas mileages when using only 5th on
>> the highway and when using 6th mostly. I have one trip I do lots to get
>> bush camping which is 201 km from gas station to gas station so I have
>> an easy check point.
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's - Gone to the rust pile...
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590
>> (More Off Road album links at bottom of the view page)- Hide quoted text -
>>
>> - Show quoted text -
>
> So, assuming that my speedometer is correct, running approximately
> 2500 rpms in 5th gear at 65 mph will NOT hurt my engine or cause
> increased engine wear? If I were to shift into OD (6th), what is the
> approximate rpms that I should be running so as to not cause lugging
> or increased engine wear?
>
> THANKS
>

Running in the higher gear is the bad thing, not running in the lower.
Lugging is bad.

'You' engine has it's own 'sweet spot' of the rpm where it seems to run
the best with the best response and best mileage. That is usually where
it likes to sneak to when you are not paying attention.

In 'my' engine's case this is 2300 rpm. Anything below 2000 on the
highway starts the 'lugging' process and causes engine 'ping' or a
rattling noise under load.

1750 or my OD (5th) at highway speeds is way too low for my setup.

Mike