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Author Topic: PD4104 from Highway traveler to Highway Hauler  (Read 3012 times)
johns4104
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« on: February 09, 2012, 07:17:39 PM »

I changed out the final drive in my 4104 and picked up 10 Mph at 2100 rpm.
So if my calculations are right I should have a top speed of 97mph, if there is enough motor.

Well I could install a turbo and change to countersunk shave rivets, and 24.5 tires might get me over 100mph.
Lets see maybe a trip to Bonneville will be in order. LOL


What about Stopping, I think I need to install my Jakes!

Does anyone know where I can find a tall 6-71 valve cover.

Thanks,
John
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
scanzel
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« Reply #1 on: February 10, 2012, 05:49:02 AM »

If you do Bonneville you better at three parachutes to the back of the bus.
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Steve Canzellarini
Berlin, CT
1989 Prevost XL
5B Steve
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« Reply #2 on: February 10, 2012, 06:07:55 AM »



   For extra power, awhile back there was a thread about the poor mans turbo, someone mentioned about

   changing the blower drive gear. I haven't a clue to what it is or what the results would be.  Might want to

   check into it for "EXTRA POWER"   Maybe someone will clue in!


   Steve 5B......
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Rick59-4104
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« Reply #3 on: February 10, 2012, 07:17:52 AM »

 I have seen different 4104 top speeds posted here and there, I ran I-40 Little Rock to Fort Smith a while back with my new Firestone 24.5's my GPS told me top speed was 74 MPH. Guess I cannot run with John Wink

Rick
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NW Arkansas
1959 GM 4104  No. 4115
1972 Grumman Kurbmaster Stepvan Conversion
1957 Airstream 13 panel Overlander
johns4104
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« Reply #4 on: February 10, 2012, 07:56:18 AM »

If I can't find a tall Valve cover, I think I will start working on the parachutes!
I don't know if changing the blower gears will help or not. seems like there was a debate as the extra horsepower needed to run the blower if it would help?

Rick, it also depends on what the gov. is set at.
anyone?
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
seaton@mta
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« Reply #5 on: February 10, 2012, 08:52:37 AM »

I had a TDH 5106 (GM Old Look Transit with two-speed auto) that would top out at 75.  The previous owner had used it as a charter bus and swapped out the original rear-end for one from a PD 4103.  So, I guess a 90 mph 4104 shouldn't be out of the question.

-- Seaton
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wg4t50
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« Reply #6 on: February 10, 2012, 10:05:08 AM »

100+ mph, no problem with MCI-7 with either 12V-71 or 8V-92, 3.73 rear, 12R24.5R tires & RTO910 @ 2500 rpm.   Grin
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MCI7 20+ Yrs
Foretravel w/ISM500
WG4T CW for over 50 wpm for ever.
Central Virginia
johns4104
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« Reply #7 on: February 10, 2012, 10:29:20 AM »

Dave,
Sounds like a fun Mci-7! Grin
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
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« Reply #8 on: February 10, 2012, 11:20:05 AM »

  You could have got away doing 100 in a Bus 20 or 30 years ago, today they would likely imprison you for a very long time.

  I looked at a 4106 in Minnesota once that JD had for sale. It had a speeding ticket framed above the driver for 86 mph. And yes, I checked and it had the correct plate number on the ticket that matched the Bus. Hate to blow a front tire at that speed, might be quite a thrill.

  No idea how my -5 is geared or how accurate the speedo is, but bringing her home the old girl would roll if I wasnt paying attention, several times seen the needle over 80.

  Guess you could always turn up the governor, lol. Crazy crazy people, I tell ya.
 
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gus
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« Reply #9 on: February 10, 2012, 02:25:15 PM »

Taller diff gears with a Spicer 4sp will give you fits starting on any incline!!
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PD4107-152
PD4104-1274
Ash Flat, AR
wg4t50
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« Reply #10 on: February 10, 2012, 06:54:00 PM »

Johns3104,, Yes, best toy I ever had, 12V-71 is magic and class, the 8V-92 is just power, no class, Have had a lot of fun preventing cars from passing on the inside, I tend to run with traffic in left lane in those days, I-95 North bound from Arcadia event, in Ga, some yankees would try pass on right as I kept a comfy distance from traffic ahead, when I saw them start inside, I could take the hole away from them, guess it made some hot headed, but I laughed, from 75 to 85&90 is quicker than the car could get past me.  Lots of fun.
After a few go rounds, I would get in right lane for a while then get back in the fast lane.  Boys & Toys
If you  see a MCI7 with a large radiator across the rear, good chance it is the one.
Maybe the guy who owns it now will chime in one day and tell of his amazement with the power.  (Troy are you listening?)
« Last Edit: February 10, 2012, 06:55:43 PM by wg4t50 » Logged

MCI7 20+ Yrs
Foretravel w/ISM500
WG4T CW for over 50 wpm for ever.
Central Virginia
RJ
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« Reply #11 on: February 10, 2012, 10:52:46 PM »

John -

The stock rear axle in a 4104 was 4.125:1 with 1:1 bevel gears.  If the very rare "HydraShift" option was chosen, then there was a 3.55:1 ratio that went along with it, same bevel gear ratio.

So what did you find and install?

Am also curious to know what size wheels (22.5 or 24.5) you're running.

Have you made a run yet with an accurate tach and a GPS to sync rpm to speed?  Would be interested in your findings.

FWIW & HTH. . .

 Wink
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RJ Long
PD4106-2784 No More
Fresno CA
johns4104
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« Reply #12 on: February 11, 2012, 09:00:39 AM »

Gus,
I thought about that, (starting on an incline)
Here was my BUS NUT logic:
I make a trip across the country at least 1 time a year.
I try to minimize taking off on an incline.
My bus weighs less than 22k loaded with water, fuel, fuel(gen), gear and 6 passengers.
The factory set up was designed for about 32k gvwr
The 3.555... to 1 ratio was an option on the 4104, in fact I took it out of my parts bus.
Also the bus came with 11-20's (12-22.5) from the factory and I am running 11r-22.5's.
So that is just a tad lower than the set-up I took the gear out of.
Also the 4106 runs an effective 3.33 to 1 after angle drive and the 4.125 rear end with the 11-20's (12-22.5's).
So again my clutch should hold up ok.

RJ, I made a run and I am turning 2100 rpm at 70Mph With GPS.
I don't shift out of 3rd gear until I hit 55 mph.
My Detroit's gov. is set at about 2500 rpm, HN70 injectors, (advanced timing maybe) that is where I get the theoretical top speed!
Now it feels like I am going 80 MPH backing out of my shop! LOL!!!
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
RnMAdventures
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« Reply #13 on: February 11, 2012, 01:06:28 PM »

It seems like my ole 4104 would run about 65 and it had the 11-20's on the rear. I don't remember what the rear end ratio was.

John, The small pic of your 4104 looks nice. Do you have any pics on the web we can see?
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Mike & Rosemarie
1964 PD4106-2626
DD8v71 & Allison v730
johns4104
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« Reply #14 on: February 11, 2012, 04:24:21 PM »

Mike,
Sounds like you had the 4.13 final drive in your 4104. That's what
I had in my 4104 to start with.

I have a couple of pictures in the post your bus section.
I may have to put build a project bus thread.

John
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
roadrunnertex
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« Reply #15 on: February 12, 2012, 07:27:26 AM »

Many years ago I bought a 1960 PD-4104 serial number 5025 ex Peoria Rockford coach.
Before it was converted to a motor home and just a shell we would take it on vacation and long trips lot's of fun back then.
It had the high speed rear end and 12R/22.5 tires and the engine was running around 2000 rpm give or take a few.
On flat interstate like I-10 it would run in the Monfort/left lane with out any problem.
Fun part would be passing a Greyhound MC-9 or a Trailways model 10 Eagle and watching them fade away in the rear view mirror.
Had a bus buddy follow me with my Toyota one day and he said that the old PD4104 would leave him and go out of sight and he was doing over 80MPH trying to stay with me.
Sad to say I converted the coach and sold it an I now own a P8M4905A with a V730 and it's 65mph cruse now it tops out at about 75 mph with the foot feed aganist the stop.
Good luck with your 4104 you to can now run in the Monfort Lane. Grin
jlv
 
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gg04
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« Reply #16 on: February 12, 2012, 10:10:11 AM »

running 3.55's with 11r24.5's same dia as original 20's..671ta ddec set at 2800rpm top.. torque and hp turned up..have only put on 86000miles since swap but..11.46mpg average and boy is it fun to drive down the road..rdw....
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If you personally have not done it  , or saw it done.. do not say it cannot be done...1960 4104 6L71ta ddec Falfurrias Tx
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« Reply #17 on: February 12, 2012, 12:50:00 PM »

How about a nice 750 hp / 2200 tor Cummins Big Cam 855 governed at a mild 2500 rpm turning 2.76 rear gears with a .75 OD 10th gear running heat treated 11R X24.5 tires.  Works out to around 150 mph!  Only problem is I sold my Crown Supercoach.  Oh well.  HB of CJ (old coot) Smiley Smiley Smiley
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johns4104
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« Reply #18 on: February 12, 2012, 02:37:52 PM »

gg04,
That sounds like a nice set-up. and only 86k miles on it! LOL
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
gus
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« Reply #19 on: February 12, 2012, 06:19:31 PM »

John,

I'm just going by my experience in the 4104 for five years and 75,000 mi. I got caught a few times when I had no choice but to slip the clutch and it hurt to have to do that, diesel engines are very hard on slipping clutches. What I did was kind of rock it so the clutch didn't slip but an instant at a time. It doesn't take long to get smoke. It keeps one alert!

Most of my problems were in RV parks, at state parks and at stop signs on steep inclines.

It is really nice with the AT in the 4107 not to have to worry about it anymore!

I used to know the rear ratio on it but have forgotten but it is pretty much a stock bus.

I think that the original 11-20 bias tires are about the same diameter as the 11-22.5. The 22.5 only means it is tubeless.
« Last Edit: February 12, 2012, 06:21:20 PM by gus » Logged

PD4107-152
PD4104-1274
Ash Flat, AR
luvrbus
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« Reply #20 on: February 12, 2012, 06:40:18 PM »

Johns4104 gg04 does have a nice setup the 6L71 DDEC set a 330 hp will get there on less fuel fwiw they are not hard to build you really don't need a DDEC 6L71 engine or the 6L71 ECM either to build one, come to valley in May I am getting ready to build one for a guy but it's going to be a right hander with a air to air charger not a aftercooler we are going for 400 hp

good luck
« Last Edit: February 12, 2012, 06:58:36 PM by luvrbus » Logged

Life is short drink the good wine first
johns4104
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« Reply #21 on: February 12, 2012, 08:41:26 PM »

Gus,
The 11-22.5 are actually equal to the 10-20's tube type wheels. 12-22.5 are the 11-20's.

Cliff,
I may just have to come up and see it.
I bought my parts bus with a fresh rebuild, 4 valve head, and a turned down blower speed for a turbo set-up.
In fact it didn't run too well because it was not sucking enough air. lol

Thanks,
John
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PD4104-1859
In Sunny Arizona
Apache Junction Near Phoenix
gus
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« Reply #22 on: February 13, 2012, 02:48:48 PM »

John,

You are probably right but I'm too lazy to go out in the cold to check what the originals were. I thought they were 11:00 x 20 but maybe not.

Since 11:00 it the max tire width it makes sense not to change that.

Strangely, the GMC bus specs website doesn't list tire sizes?
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PD4107-152
PD4104-1274
Ash Flat, AR
RJ
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« Reply #23 on: February 13, 2012, 09:41:52 PM »

John & Gus -

The OEM tire size on the 4104 (and 4106/07) were 11.00x20.  It's listed in the sales spec sheets.  When radials came out, 12R22.5 became the OEM tire on the GM Parlor Cars.

But more importantly, you need to know that the whole powertrain was based on tires that turned 495 revs per mile.

So, regardless of whether you want to use 11R22.5, 12R22.5, 11R24.5, 295/75R22.5 or 315/80R22.5, you need to look at the manufacturer's specs for the revs per mile, as well as the load range for the appropriate weight capability for your coach, when buying tires.

Using tires that turn MORE than 495 revs/mile will lower your top speed, as well as increase your fuel consumption somewhat.

Using tires that turn LESS than 495 will have the opposite effect.  (Might make incline starts a little more challenging, too.)

FWIW & HTH. . .

 Wink
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RJ Long
PD4106-2784 No More
Fresno CA
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« Reply #24 on: February 14, 2012, 08:13:08 AM »

My 1960 4104 has a top speed of 62mph on a flat road. (GPS speedometer)
I get about 8.5mpg on the highway and about 7.3mpg local driving.

I don't know the rear end ratio or the RPM that the engine is governed at.
The tires are 295/75-22.5R Toyo.

It has a 4 valve head with N65 injectors.
It still has the original 4 speed transmission.

I guess I need to find a way to connect a tachometer and see the RPM of the engine.
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1960 PD4104-4971 - Memphis TN

Buy the new Eddie L Smith CD "STAYIN LONG" at:
http://www.eddielsmith.com
Everyone is welcome to any of our gigs listed on the website.

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« Reply #25 on: February 14, 2012, 03:52:53 PM »

When I got my 4104 it had 11:00 bias tubeless tires. I changed to Toyo 11:00 radials which had plenty of weight capacity and they seemed to me to be the exact same size. 12:00s seem too large to me, they look OK on the 4106 though but it is also a bit heavier. I could tell no difference in speeds or speedometer readings.

It did not like speeds over 62-65 mph. It would go faster but the engine sounds told me it was too fast!
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PD4107-152
PD4104-1274
Ash Flat, AR
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