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Author Topic: Speaking of rear gears...  (Read 1949 times)
ChuckMC9
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« on: November 30, 2006, 10:13:16 AM »

In a recent discussion the subject of gearing came up as Captain Ron is trying to reduce his fuel consumption.

I have an 8v71N with a five-speed Fuller and discovered only two days ago that I have 4.11 gears.

Now after my initial dismay, I'm wondering how much angst I should rightfully have.

I plan to stay away from the superslab to the degree it is possible - am much more of a blue highways kind of guy.

With the manual transmission, that engine, and those kind of roads, is having that differential so bad?

I guess I'll have to give up the manual transmission gloating factor about better mileage now...

I've always imagined that it is geared fairly low because of all you guys talking about cruising at 80+ (which I wouldn't do anyway) and mine is just about maxxed out at 67, which doesn't bother me, but it told me something was unusual.

Also, all the hand-wringing about using the clutch on takeoff has never been a problem with me. I can do DTSs in my sleep. Like a tractor, baby!

How seriously should I consider a higher ratio? Would I be a good candidate for 24.5s? Thoughts?

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Buffalo SpaceShip
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« Reply #1 on: November 30, 2006, 11:31:13 AM »

Chuck, as you can imagine, your lower gearing will come in very handy for negotiating around campsites, and backing up especially. My old '06 could do 80 against the gov... but I sold it mostly because of it's lack of low-speed manuverability. "Feast or famine," I suppose. What good was 9mpg if I couldn't get the thing backed up my driveway without flaming the clutch. 

There's been talk here about those Road Ranger or RTO trannies, with 7-13 speeds, splits and ODs. You'll occassionaly find 'em in a coach. And would make a nice upgrade, for sure. TomC knows an aweful lot about these things, seems. For a bussin' lifestyle, these truck-type trannies, with granny and superslab gears is really far superior to either a high-geared coach or a low-geared one with only 4-5 forward speeds.

And MPG would still beat the stuffin' out of any slushbox. Clutching would be a breeze. Snicking gears would be a pleasure, matching the somewhat small torque range of rpms of a two-stroke DD.

Not "feast or famine". But "the best of both worlds", IMHO.

Just some ideas... 'cause when you got a t-drive, you got options, sir.

HTH,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
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« Reply #2 on: November 30, 2006, 01:36:31 PM »

If it wasn't such a pain to change out the dana 2-speed heavy duty axle wouldn't seem to be a bad idea.

http://www2.dana.com/pdf/AXSL-0321.PDF

They have one with a 3.70 and 5 something ( sorry closed window..)

I would bet a combination of a B500 with a 2-speed axle would really make a highway flatten out.

Hmmmm..... Just a thought.....
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Buffalo SpaceShip
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« Reply #3 on: November 30, 2006, 02:29:39 PM »

Interesting idea, Dave. There's also a 3.55/4.83 that might be a great superslab/ stump puller combo. Hmm.... Dunno what's harder, a tranny swap or a rear-end one.

Chuck, I forgot to mention, unless you're currently running 11R22.5s (I'm assuming you have the std. 12R22.5s), going up to a 11R24.5 will only give you a few revs per mile at most. They're almost identical diameters. And the 12R22.5s handle more weight and have a better ride due to the bigger sidewall.

I'm finding that they are a bee-otch to find, those 12R22.5s. But every HD tire shop has the 24.5s coming out 'der ears, since the big rigs run 'em.

HTH,
bb
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Brian Brown
4108-216 w/ V730
Longmont, CO
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« Reply #4 on: November 30, 2006, 03:40:00 PM »

When I put a 60 series with 741 in my eagle 01 it would outdrag just about anything from the stop light but was all done at 72. Got tired of running the engine at or near red line all day so changed form the stock 3:73 gear to a 3:36 ( the biggest the would fit). Now only beat some of the guys at the stop light and don't want to find out what the top end is! Did up fuel mileage by 12% - strangely enough the is also what the difference in the gearing is! Was it cost effective?? Cost of new gears, bearings,labor, etc was $4400.
Just my way,Your mileage may vary
JimH
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Started with nothing - still have most of it left!
1963 Eagle 01 with Detroit 60 series done (Gone-sold!)
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Dreamscape
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« Reply #5 on: November 30, 2006, 05:49:17 PM »

Jim H.

This is kind of off this topic, sorry Chuck.

How difficult was it stuffing the 60 in your 01?

I have an 01 and would like to consider that someday, after we win the lotto. Grin

I will read this thread for some ideas on our coach, as the gearing is too high with this 4 speed crashbox. Interested in anything that would work. 1st and reverse are ridiculous.

Paul

Dreamscape
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buswarrior
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« Reply #6 on: November 30, 2006, 07:53:30 PM »

Hello

Many claiming 80 mph need to validate the accuracy of their speedometers, and the older coaches capable of 80 face serious disadvantages in driveability when the road rises in front of the coach.

A 1:1 transmission won't let you run that fast without screaming the engine to well beyond the "battle" setting....so forget about it!

Using Mallie's speed calculator  http://www.cwis.net/~mallie/page12.html 

4.11 gear at 2300 rpm with 495 rev tires gives 68 mph
  same at 2100 rpm gives 62 mph
  economy cruise at 1900 rpm gives 56 mph
  downshift point to catch 4th gear 1500 rpm gives 44 mph

3.7 gear at 2300 rpm with 495 rev tires gives 75 mph
  same at 2100 rpm gives 69 mph
  economy cruise at 1900 rpm gives 62 mph
  downshift point to catch 4th gear 1500 rpm gives 49 mph

IMHO, your coach will have better driveability on secondary roads, with 5th being more usable at a slower road speed. I also suspect that 3rd gear will be more useful in town than a taller geared coach. Also, 2nd gear starts might be reasonably possible, if the weight is kept down in the conversion.

In town, the 5 speed sticks with the tall rear gear were a royal pain, there was no good gear to use. 2nd was too slow, and 3rd wouldn't pull out from low revs. Big difference from the 4 speed coaches, where 2nd covered the in-town territory quite nicely.

As far as real world fuel economy, unless you are blasting flat out back and forth on the interstate, two coaches operated side by side up and down and around on secondary roads, the fuel economy advantages, and the driveability advantages will be traded back and forth between them as to conditions in which short and tall gears are the more efficient. Net difference will be small, and in the right conditions, the 4.11 coach might use less fuel!

All things being equal, the 4.11 will pull the hills slightly better, and allow the use of top gear more often and longer than the 3.7 coach on secondary roads, defeating the up front gearing advantage of the 3.7 coach.

It sounds like you'll be very happy with what you have unexpectedly found!!!

Merry Christmas?

happy coaching!
buswarrior

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TomC
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« Reply #7 on: November 30, 2006, 10:40:49 PM »

The easiest, or more to the point, cheapest thing to do would be to put a 10spd overdrive Roadranger in there.  I personally switched from 12R-22.5 to the 11R-24.5 since as an old truck driver knew that the 12's were hard to find on the road.  If you use the 16ply 24.5's, the weight carrying capability is with in a very few hundreds of pounds.  Also, they are about a half inch taller and 5rpm less per mile.  If using the B ratio box which is very common, it has a 11 to one start and a .75 overdrive.  With the 12R's, and 4.11's in overdrive you'd have 1612rpm at 65 and 1861rpm at 75.  Not only that, your startability would be  (based on 50,000lb) 24%.  If you're going to stay with a manual, I'd go with either the 9 or 10spd overdrive.  I personally like the 9spd better since you're basically repeating a 4 spd H pattern, rather than the 10sp where you have to go from the 5th spd back to 1st (commonly called the U shift).  Course, a good World transmission set at 5spd would be excellent also.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Al Bass
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« Reply #8 on: December 01, 2006, 12:04:32 AM »

I have 411 gears and a 9 speed roadranger with .73 over in 9th gear, 350 Cummins and 22.5 tires . Pulling 27,000lbs with Jeep in tow. At 1500 rpm in 9th I'm running 61 mph, if I was running in 8th gear (1 to 1)  I would have to turn 2000 rpm for the same 61 mph.
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keithshotrodshop
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« Reply #9 on: December 01, 2006, 06:11:46 AM »

In my silversides I have the standard 4 speed with a 4.11 rear end. On my way back from california she would max out around 70mph, but got me 12mpg flat the whole way home, which is better than my Daily Driver Silverado!
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ChuckMC9
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« Reply #10 on: December 01, 2006, 07:31:23 AM »

It sounds like you'll be very happy with what you have unexpectedly found!!!
Merry Christmas indeed! Thank you for your trouble especially, Buswarrior. And all others too! Someday when I've got all the time in the world (yeah, right) I'll think about some more studly swaps. In the meantime, I'm gonna feel much more comfortable with what I've got.

I'd forgotton about Mallie's speed calc. Thanks for the reminder!

(PS to BW: I still haven't installed those taillights yet! Smiley
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Buffalo SpaceShip
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« Reply #11 on: December 01, 2006, 07:48:53 AM »

Speaking of gear/MPH calculators, try Daris Bouthillier's. It even puts speeds in engine rpm... http://www.thebouthilliers.com/4106/calcmph.html  It's awesome.

bb
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Brian Brown
4108-216 w/ V730
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« Reply #12 on: December 01, 2006, 08:45:51 AM »

Thanks Chuck.

My own set are still waiting too!!!

I always feel guilty to accomplish tasks related to broken stuff, not stuff that still works!!!

happy coaching!
buswarrior
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kingfa39
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« Reply #13 on: December 01, 2006, 02:32:46 PM »

i have a 4106, when i had the spicer, 12-22.5 tires i could run 80+ with a calibrated speedometer against the gov and got 10+ mpg, the rear end is 411, i put automatic in it now it goes 76 and gets 7.5 mpg, i would not personally go to automatic again if i ever get another bus. did it so wife could drive, then she wouldnt drive anyway
Frank Allen
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