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Author Topic: Driving in 3rd gear?  (Read 4385 times)
buswarrior
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'75 MC8 8V71 HT740




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« Reply #15 on: February 13, 2011, 08:26:24 AM »

roughly speaking, with a 3.36, 50 mph is 1400 rpm in 4th, and 55 mph is 2100 in 3rd/1500 rpm in 4th.

with a 3.7, 46 mph is 1400 rpm in 4th, and 50 mph is 2100 in 3rd/1530 rpm in 4th.

Most Allisons are thinking hard about downshifting around 1400 rpm.

Ed, how are your seals around the rads? Rads in good shape? Engine hot-rodded without a cooling upgrade?

Your strategy is exactly the right one to compensate for a cooling problem, get the fans spinning, and the water pump pumping by keeping the rpm's high.

You might have a simple fix?

On mine, I left the ratty rubber seals around the new rads in place to act as a form, and spray foamed all the way around. Easy to dig it out the next time. You want absolutely NO air sneaking past, you want it all going through the rads. Also, check the door seals on the fan compartment. I continue to tape mine to seal them from the outside until  I work out a better style of seal from available bits and pieces. The old ones are hard, and the door doesn't faithfully fit against them anymore. Coloured duct tape to match the paint looks ok.

Most "lugging" problems stem from a lazy (or uninformed) driver not downshifting a manual transmission when they should, and let it drag down and down, typically, the top of the hill is approaching...trying to save the shift down and the shift back up again. 2 stroke Detroits heat up very badly by doing this. Piston temps, they say, get to destruction temps.

A properly operating automatic really won't let you easily "lug" the engine.
Speed drops off, and then it downshifts, whether we like it or not!

happy coaching!
buswarrior

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Frozen North, Greater Toronto Area
Ed Hackenbruch
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« Reply #16 on: February 13, 2011, 04:19:42 PM »

Seals are in pretty good shape, never had reason yet to pull the radiators out, engine not hot rodded, has the n60 injectors, no turbo.  My allison wants to downshift at about 1440 to 1450 rpm.  Smiley
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
gus
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« Reply #17 on: February 13, 2011, 04:30:40 PM »

Brian,

I agree, I've run the 4104 many miles in 4th on flat ground or slight downgrades at very low speeds, that is not lugging, that is almost coasting.
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PD4107-152
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Ash Flat, AR
Busted Knuckle
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« Reply #18 on: February 14, 2011, 07:03:03 AM »

BW why does it matter what the driver is wearing?
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
www.kylakesidetravel.net

Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
buswarrior
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« Reply #19 on: February 14, 2011, 07:14:55 AM »

yup, I knew someone would...

roflmao!  Grin

happy coaching!
buswarrior
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Nellie Wilson
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« Reply #20 on: February 15, 2011, 03:00:40 AM »




BW why does it matter what the driver is wearing?
Grin  BK  Grin

Huh?

yup, I knew someone would...

roflmao!  Grin

happy coaching!
buswarrior


Huh?

I get the 'lmao' part, but what's the 'rof' part mean?

Nellie
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Had to change a tire... Angry  got to put it on backward... Undecided  still trying to fix it on photoshop... Huh Roll Eyes Huh
DMoedave
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« Reply #21 on: February 15, 2011, 03:42:03 AM »

guessing its read as un-uniformed bus driver.   rof =rolling on floor.
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we love our buses!!! NE Pa or LI NY, or somewhere in between!
buswarrior
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« Reply #22 on: February 15, 2011, 07:54:18 AM »

Please, please, take me in and feed me.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
RJ
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« Reply #23 on: February 15, 2011, 10:20:24 PM »

Nellie -

Since my French is SO bad, let me try and translate BW & BK's exchange from English into American for you:

#1:  BW said "Most "lugging" problems stem from a lazy (or uninformed) driver not downshifting a manual transmission when they should. . ."  What he meant was a non-educated driver, not one who was out of uniform.


#2:  BK then asked "BW, why does it matter what the driver is wearing?"  Here BK is making a (bad) pun or joke out of the single letter difference between un-in-form-ed (not educated) and u-ni-form (clothing).


#3:  BW's response "yup, I knew someone would..." is simply acknowledging that BK put together a bad pun using BW's own words.


As for BW's last response about needing to be fed, you, of all people, should understand how fellow countryman BW is suffering.  After all, he's stuck with Big Transit during this time of year while you've fled to FL.

The men in the white coats will be along soon to assist in easing BW's suffering!


Next time you run across an Internet Acronym that you don't understand (roflmao or obama), you can look it up here:

http://www.gaarde.org/acronyms/

Oh, wait, obama is not on the list - yet.

FWIW & HTH. . .  (For What It's Worth & Hope This Helps)

 Wink
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RJ Long
PD4106-2784 No More
Fresno CA
Nellie Wilson
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« Reply #24 on: February 16, 2011, 03:50:01 AM »

My Dear RJ -

You saved me from a long sleepless night. Maybe if I read enough I'll develop some 'board intuition,' but right now lots of things fly right over my head.

Same to you, DMoe (gee, why couldn't I figure all that out?)

(RJ - Better watch that political talk... got some pretty scratchy viewers out there) Grin Wink Smiley

Quote
Please, please, take me in and feed me.

Really? C'mon over, BW... you'll like the weather.

Nellie

Oooppps! Guess the sleepless night already happened. Oh well, I like morning snoozes. Smiley

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Had to change a tire... Angry  got to put it on backward... Undecided  still trying to fix it on photoshop... Huh Roll Eyes Huh
NCbob
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« Reply #25 on: February 16, 2011, 08:36:10 AM »

Brian, since I too have the 4 speed in a 5A I feel somewhat qualified to put my 2 cents in with the rest. My personal parameters are stay in third in traffic and not concern myself unless traffic starts to move along at a consistant 55 MPH, That holds my engine RPM's at about 1800 and allows my Jake's to still be somewhat effective (should I have them switched on) and need them. I have no compunctions of keeping in 3rd at 55 for prolonged periods as I'm maintaining no more engine revs than I am at 65-70 in 4th.

I'd rather have the help in fast braking, if necessary, from both the engine falling revs and the Jake's than have to make a panic stop with brakes alone.

FWIW

NCbob
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True friends are difficult to find, hard to leave and impossible to forget.
NCbob
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« Reply #26 on: February 16, 2011, 08:37:30 AM »

Sorry Steve, guess my noodle isn't on straight today.

NCbob
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bevans6
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« Reply #27 on: February 16, 2011, 08:58:53 AM »

NCBob, you must have lower gearing than I do.  I have a 3.7 diff, and with 495 rev/mile tires I tend to be on the governor around 2150 rpm at 70 mph, and at around  53 mph in third gear.  I run 45 - 50 mph in fourth all the time, that's 1375 rpm to 1525 rpm (if my calculator and my mind are both working right, which is always a question) and shift down to third if I can't accelerate in that gear/speed, and of course if I run along into an uphill grade or want my jake brakes to actually do something useful...  As noted, that's kind of coasting along.  Light throttle, temps stable at 180, listening to country music on the radio... Smiley

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
Len Silva
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« Reply #28 on: February 16, 2011, 10:05:58 AM »


Next time you run across an Internet Acronym that you don't understand (roflmao or obama), you can look it up here:

http://www.gaarde.org/acronyms/

Oh, wait, obama is not on the list - yet.

FWIW & HTH. . .  (For What It's Worth & Hope This Helps)

 Wink


OBAMA  Our Blessed America Moves Ahead
    or
Our Best Alternative Miraculously Appears
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bevans6
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1980 MCI MC-5C




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« Reply #29 on: February 16, 2011, 10:24:52 AM »

For the other side of the house, and only to amuse myself...

OBAMA - Oh bother, a militant arab

for Nellie - Oh boy, a musical apparition!*

for our Jewish friends (specifically a guy named Mike Rosen who used to go Yiddish on me from time to time, and in no way intended as a jibe at President Obama, a man whom I have deepest respect for...)

Oy, bupkes, another meshugener already!

my contribution to thread drift for the day...

* Apparition can be defined, if you follow the lexicography a bit, as a "phantom of loveliness", so appropriate for our Nellie, who sometimes disappears...

Brian
« Last Edit: February 17, 2011, 05:11:04 AM by bevans6 » Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
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