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B61 W 7.88 Gear Ratio How Fast / Slow Mph ?


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I've got a B61 with those gears and a non turbo 711 and I haven't really topped it out but I think it does around 55-60mph.

My B-61 with 6.34 rears, double over quadraplex, on 10.00X20 rubber runs 57 mph at 2150 rpm.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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Macks were built to move mountains with minimum horsepower and a lot of gear advantage.

If you haven't done so already -

Go online and find a gear ratio or final drive ratio calculator - there are lots of them and they are easy to use.

Feed it the required data - tire diameter, max or desired rpm and final drive ratio (including any overdrive multiplier) to get the speed at that particular rpm.

7.88/1.00 is probably too much gear for a road truck. Great for pulling a load though! If your truck will be used in a lot of parades or other fairly slow activities, it might be real good, but you won't be passing too many people.

Even with a .65 overdrive, the final drive is over 5.12/1.00, which is still a pretty low final drive ratio by today's standards.

Paul Van Scott

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ok i nned to know the appox mph on a mack b61 671 turbo quadraplex 5/ 4 goes in to o/d in 4 th with 7.88 gear ratio any one have a good idea of the top mph ? thanks !!

Why did somebody put a 671 Detroit in your B61?

Or did you mean "ENDT673"?

I didn't bother doing the calculations, but on 10:00x20 or 11R22.5 rubber I'd suspect about 48 - 50 MPH @ 2100.

.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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48.3 MPH @ 2100 RPM with a TRQ7210 quad box (.69:1 overdrive) 7.88:1 rears on 10:00x20 or 11R22,5 rubber.

.

Hi Herb, what is the difference between a TRQ-7210, and a TRQ-7220? I've never seen the former myself.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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Hi Herb, what is the difference between a TRQ-7210, and a TRQ-7220? I've never seen the former myself.

Rob

A .69 overdrive in the 7210 vs a .70 overdrive in the 7220, and a couple of other miniscule differences in ratios of various other gears.

You can't tell any difference in the way it shifts compared to a 7220.

I had a TRQ 7210 in that B613T with the turbo 711 that I made into a dump truck in 1981, and the company I worked for back when I was a teenager had a B61 10 wheeler dump truck with a TRQ7210.

.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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  • 2 weeks later...

hi yes its a 673t i thought i got the 671 wrong thanks

Why did somebody put a 67 Detroit in your B61?

Or did you mean "ENDT673"?

I didn't bother doing the calculations, but on 10:00x20 or 11R22.5 rubber I'd suspect about 48 - 50 MPH @ 2100.

.

just throttle on it till you see vapor trail out both mirrors, hood sets up a nice vibration,,,(vapor trail needs to be white though,,,,not blue and smelly)

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A .69 overdrive in the 7210 vs a .70 overdrive in the 7220, and a couple of other miniscule differences in ratios of various other gears.

You can't tell any difference in the way it shifts compared to a 7220.

I had a TRQ 7210 in that B613T with the turbo 711 that I made into a dump truck in 1981, and the company I worked for back when I was a teenager had a B61 10 wheeler dump truck with a TRQ7210.

.

Also, Mack calls the TRQ7210 a 14 speed and the TRQ7220 an 18 speed although they are both shifted the same way.

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Macks were built to move mountains with minimum horsepower and a lot of gear advantage.

If you haven't done so already -

Go online and find a gear ratio or final drive ratio calculator - there are lots of them and they are easy to use.

Feed it the required data - tire diameter, max or desired rpm and final drive ratio (including any overdrive multiplier) to get the speed at that particular rpm.

7.88/1.00 is probably too much gear for a road truck. Great for pulling a load though! If your truck will be used in a lot of parades or other fairly slow activities, it might be real good, but you won't be passing too many people.

Even with a .65 overdrive, the final drive is over 5.12/1.00, which is still a pretty low final drive ratio by today's standards.

Paul Van Scott

I think that's the same ratio as the mixer-it is great in parades, and I do not pass many people on the road. Usually there's a long line of traffic behind me waving a finger at me.

Producer of poorly photo-chopped pictures since 1999.

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Why did somebody put a 671 Detroit in your B61?

Or did you mean "ENDT673"?

I didn't bother doing the calculations, but on 10:00x20 or 11R22.5 rubber I'd suspect about 48 - 50 MPH @ 2100.

.

I'd suspect about the same. I have taller tires, but i'm going to 11R22.5's as soon as I accumulate the wheels. I can do 53mph now, 55 if I stand on it going down hill.

Producer of poorly photo-chopped pictures since 1999.

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  • 2 weeks later...

:SMOKIE-LFT:

This is where my favorite gearing/tire size cruncher is:

tire size/gearing number cruncher

Speed

"Remember-ANY Gun Control is Unconstitutional!"
<!--sizeo:3--><span style="font-size:12pt;line-height:100%"><!--/sizeo--><i><b>MACK-E Model Registry # 36</b></i><!--sizec--></span><!--/sizec-->

<a href="http://www.nvabatetravel.com/"target="_blank">http://www.nvabatetravel.com/</a>

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