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Author Topic: Repower question  (Read 1735 times)
scenic791
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« on: December 14, 2012, 12:50:06 PM »

Hi guys - long time listener first time caller.

I'm working through my first ground up conversion on a PD 4501 and am getting to the point of considering a repower.  My coach currently has an 8v71 and 9-sp road ranger.  I'm fine with the performance of this combination but the uncomfortable with the reliability of my shift linkage as I've already snapped it once.  The linkage is a one-off "special" design that in my opinion was not "designed" but rather "welded up big and strong" so as not to fail.

So - my question is this, could I consider using a light-duty 3/4 pickup engine/trans in my 30k lb empty coach?  I realize this may be an amateur question but please explain to me why it won't work or is a completely useless idea.  My thinking is driven by space concerns and the desire for modern/electronic linkage and controls. 

Ok guys - light me up.  I can take it - I think. Smiley
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Red Rider
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« Reply #1 on: December 14, 2012, 01:11:13 PM »

sounds to me like "unpower" rather than "repower". I never heard of a 30k light duty pick up truck.
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Mike AKA; Red Rider 4106-1885
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« Reply #2 on: December 14, 2012, 01:23:35 PM »

I think that the duty cycle required will to great for a 5.9 to 7 litre diesel.    Looking at a 8.3 ltr Cummins or smaller CAT engine would make better sense.   One could purchase the powertrain from a wrecked Class A motorhome.   Another thought would be to pick up the smaller Series 50 Detroit. 
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Utahclaimjumper
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« Reply #3 on: December 14, 2012, 01:53:56 PM »

 Your first part say's I'm fine with this combo,,, next your saying I want to change it,,just for a linkage problem??
 Clean up the linkage and spend your time in more productive ways,, a Scenicruiser can be a lot of work for a conversion, but worth the effort, and the 8V71 is a perfect engine for it.>>>Dan ( A non Detroit would be sacrilege for a sceni)
« Last Edit: December 14, 2012, 01:56:15 PM by Utahclaimjumper » Logged

Utahclaimjumper 
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scenic791
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« Reply #4 on: December 14, 2012, 02:45:02 PM »

Thanks for the feedback guys.

RedRider - not sure I understand the "unpower" comment.  Keep in mind i'm not by any stretch a motor guru but I was seeing this swap as more of a small upgrade from what i've got.

ZeroC - I agree a motorhome unit, small Cat or larger Cummins would be great but I think I don't have room for a straight 6???  Anybody have experience there?

Dan - I do like the 8v that's in there and have no qualms about it performance wise and will upgrade the linkage if I don't find a better solution.  It was unsettling when the linkage snapped (without me knowing it) and I let my foot off the clutch and nearly punched a whole through the side of my shop.  I think i'm emotionally scarred into thinking wires are more reliable??? 

Again - thanks everybody, I do appreciate all the helpful ideas.

Tim
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« Reply #5 on: December 14, 2012, 03:42:09 PM »

I think what Red Rider was alluding to is the difference in TORQUE that you would be losing with a 3/4 truck engine. I frequent many RV boards and hear complaints about lack of power with a 5.9 Cummins in a heavy vehicle.
 My present motorhome has the 8.3/6 spd. allison combo, and at 330HP is a very good combonation of power and economy. I have also had GMCs with the 8V71, and at about the same weight had good power and reliability, I would think the Detroit and 9 spd. would be a desired combo because this engine likes to spin and the trans you have would keep it spinning. I wish you luck with the Sceni, ( its not "Scenic") its the holy grail among GMC owners and gets attention where ever it goes.>>>Dan
« Last Edit: December 14, 2012, 05:47:15 PM by Utahclaimjumper » Logged

Utahclaimjumper 
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« Reply #6 on: December 14, 2012, 04:51:36 PM »

The 8V71 you have in your bus is a "heavy duty" engine, designed to run 24/7 in commercial service. The bus would run day and night, and just get fresh drivers at the bus depot. It only got shut down to do oil changes. A pick up diesel won't be able to take that kind of use.

I would keep what you have and fix the shift linkage.

A repower would be nice and a lot of fun if you like doing that kind of thing. But it would be a lot of work and a lot more money than you think.

JC
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JC
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« Reply #7 on: December 14, 2012, 05:18:43 PM »

There is plenty of room to put a straight 6 in the Scenic. Pat McNeil put a series 60 in his.
A series 60 (6 cyl) or a series 50 (4 cyl) are taller than most other engines, so you'll need to measure closely to see what other modifications are needed to accomodate the height.

The 8V71 is a very nice engine that is well suited for your coach. I believe you will be better served by fixing the linkage.
 In 'Greyhound tune', the 8V71 produced 270 HP & in the neighborhood of 800 ft-lbs of torque & did so for over 200k miles if driven & maintained properly. Will be difficult to match those numbers with a medium duty truck powertrain & impossible with one out of a light duty truck.

Good Luck & welcome to the madness!
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« Reply #8 on: December 14, 2012, 08:16:07 PM »

The shifting issue is very simple to fix with a very fine setup.  I have now done two RTO910 shifting systems, one in a MCI7 other like your  Scenic, used the Kenworth Cabover cable shift used on later cab overs. The entire setup NEW price was about $1,000.00.   A very smooth shifting, much better than a cab over with the mechanical linkage and near to a conventional.  They have both units, one for the front and one for mounting on top of the Road Ranger.  The MCI7 took 32' ea HD Morse cable setup X two. 1 for neutral, 1 for gear selection. Like to mention again, very smooth with good feel.  The Scenic we did used the 8V-92, used the 150 injectors, 2600 rpm, 3.73 rear, 11R X 24.5 476 rpmile, do the math, ever see a Scenic at 100+mph, or for that matter a MCI7.  We both had massive amounts of fun, I of course was not as crazy as Rick with the Scenic, I only ran the 9200 injectors w/6V-92 Turbo.  Grin Shocked
Had mucho fun
Dave M
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« Reply #9 on: December 14, 2012, 08:57:06 PM »

Scenic791 (Name???) -

When Marmon-Herrington repowered all the Scenics for 'Hound in '61 & '62, they emerged with an 8V71 and 4-spd Spicer gearbox.

For the next 12/13 years they pounded the pavement all over this continent with this powertrain, until Greyhound retired the last of them in late '74 or '75.  Numerous Scenics got converted to freighters, with the whole upper deck devoted to package express.  Not unusual to see one loaded to 50K lbs, trundling along on the aforementioned powerpack.  (I've seen the now-closed San Francisco shop load four complete 8V71s on pallets in the baggage bins to be shipped to the Los Angeles maintenance facility!)  Yup, they can get real heavy!

Your coach may only be 30K now, but once it's converted, you've now exceeded the capability of a 3/4 ton pickup's diesel engine/trans by a factor of about 4x, give or take just a little. 

Or, to put it another way, if the 3/4-ton's diesel engine/trans is good for 100,000 miles in the pickup, you'll be lucky to get 25,000 miles with that combo stuffed in the tail of the Scenic.  Probably with overheating problems, too.  That's what RedRider meant, albeit a typo - it was supposed to come out "underpowered."

If you want to stick to the stick, fix the linkage and keep what you've got.

If you want a really sweet powertrain that can easily handle the weight, plus easy (less fatiguing) to drive in traffic and wiggling into/out of campsites, then consider an 8V92TA coupled to an Allison HT-740 (4-spd) or HT-754 (5-spd) automatic.  Get the mechanical engine/trans combo, you won't have to deal with electronics.  Keep the HP of the 8V92 to 400 - 425 and you'll get relatively good (for a bus) fuel mileage with minimum overheating issues.  Pump it up to 500 and you'll have a monster in the tail, with fuel mileage and overheating problems, too.

Kyle's right - you can also stuff a S-60 back there, along with a B-500 automatic, if you want to go the electronic route.  I'd stay away from a S-50 with the Scenic's weight, but you could also use a Cummins ISM. 

FWIW & HTH. . .

 Wink




PS: Please take a minute to edit your profile to include a signature line that includes at least your first name, home-base city/state and your bus make/model.  That way we can better help you, and you might find out there's a fellow busnut nearby!
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RJ Long
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« Reply #10 on: December 14, 2012, 10:19:14 PM »

With the combination of smog laws and the fact that 2 stroke savvy mechanics are getting fewer and fewer, I'd completely stay away from a repower with another Detroit 2 stroke engine. Keeping in mind that (as said before) that the 8V-71 puts out a comfortable 800lb/ft of torque without strain all day, that pretty much eliminates the pickup engines-even though they are now rated at 800lb/ft torque. Do you think they could pull that kind of power for 10, 15, 20 minutes while climbing a grade or in the Rockies? I wouldn't trust it.
The smallest engine I'd go with would be a Cummins 8.3 or 8.9, International DTA466 or 530 or even 560, Caterpillar C9. With the PD4501, I'd consider putting in a bigger 6 cylinder like a Cummins ISM, NTC or N14, Detroit Series 60, Caterpillar 3406B (my favorite) C12, C15. Then run an Allison transmission, and you'd have a bus that would just waltz up hills without fuss.  Would be really fun to drive. Good Luck, TomC
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scenic791
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« Reply #11 on: December 15, 2012, 08:31:19 AM »

The shifting issue is very simple to fix with a very fine setup.  I have now done two RTO910 shifting systems, one in a MCI7 other like your  Scenic, used the Kenworth Cabover cable shift used on later cab overs. The entire setup NEW price was about $1,000.00.   A very smooth shifting, much better than a cab over with the mechanical linkage and near to a conventional.  They have both units, one for the front and one for mounting on top of the Road Ranger.  The MCI7 took 32' ea HD Morse cable setup X two. 1 for neutral, 1 for gear selection. Like to mention again, very smooth with good feel.  The Scenic we did used the 8V-92, used the 150 injectors, 2600 rpm, 3.73 rear, 11R X 24.5 476 rpmile, do the math, ever see a Scenic at 100+mph, or for that matter a MCI7.  We both had massive amounts of fun, I of course was not as crazy as Rick with the Scenic, I only ran the 9200 injectors w/6V-92 Turbo.  Grin Shocked
Had mucho fun
Dave M



Dave - That is exactly the kind of information I was hoping to stumble across.  Can you point me in the direction of that $1000 new shift linkage set up?  As fun as 100+mph in a Scenic sounds I think i'll stick to the saner side of 80.  I'm not really excited about the cost/time of changing my drivetrain as my 8v71 is fresh but... I can't live with a questionable set up. 

I realize as most everybody has pointed out that the light duty truck driveline is not suited to this weight or a commercial duty cycle but I did want to ask the question as their power outputs (HP and LB-FT) are quickly surpassing my setup.  I'm not going to run it 24/7 uphill and change drivers on the fly so I was willing to consider a powertrain that would maybe only survive for 100k IF it were up to the task performance wise. However - i'd jump at the chance to fix my linkage problem and use my set up as is rather than pound my head against a wall that will only drive me backward.

Again I want to stress my appreciation for everyones input and I say thank you for the help!

Tim



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wg4t50
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« Reply #12 on: December 15, 2012, 11:57:43 AM »

Tim,
I found the installation of the Kenworth cab over shift system rather simple, had to weld up a bracket to mount the shift handle assy in plase of the old shift lever.  Ran the Morse cables back thru the same route as the mechanical linkage once it was removed.  On the Transmission, simply remove the 4 cap screws holding the origional shift lever, and install the new adapter that connects the cables.
I would go to you local Kenworth Truck Dealer, talk to the parts dept, hope they have an older educated  person who has been around a while.  Once I had the two parts, 1 at seat and 1 sor transmission, I measured the length of cable I needed, seens it was 32', requiresw  two cables, they are not cheap, but are wonderful.  When it was all together, I was very happy/amazed/pleased how smooth it all worked.  I did that setup about 15 yrs ago, but think Kenwood would still be using that system.

For the hot rod part of these, I am glad I did it, and no need to repeat it, Pleased that I was in a position the play the 8V-71 and for sure the two versions of the 12V-71, 1 NA other TT, that was way over the top, wheel  spin was the big issue, requiring reducing air pressure on the tag bags, sold the 12V to chap who is still smiling, not in a bus. In the end the 8V-92, while on the wild side, I knew one day it would come home on a hook.  Never happened, sold it to a chap who I think visits this forum some.  
The MCI7 is easy to spot with the large radiator across the back end.  
Yup, I still smile thinking ab out the fun playing with empty trucks and finding how few young guys know what a pair of 238's means.
Could wear everyone out with some of the things I experienced with that old bus, had it in every state east of the Miss river and into Canada some.

I will croak with a smile.
Dave M
« Last Edit: December 15, 2012, 11:59:46 AM by wg4t50 » Logged

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« Reply #13 on: December 15, 2012, 05:49:12 PM »

 Another way to look at torque numbers is:
 5.9=360ci
8.3=506 ci
8V71=568ci
14liter=854ci
Huge difference in GRUNT!!    >>>Dan
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Utahclaimjumper 
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« Reply #14 on: December 15, 2012, 06:03:18 PM »

Re engineer correctly the ONE shifter rod from your tranny to your shifter.  If all the Crown Supercoaches with 10-speed Roadrangers can have flawless shifting, (1" throws from neutral to whatever gear with 3 pounds of effort) soos can you.  Be prepared to use several tight small U-joints in the rod with a small telescoping section, plus many pillow blocks with lots of grease zerts.

Chuck that 9 speed.  Probably a very poor choice for your Scenee.  You want a RT or RTO or RTOO 910 or 11510 10 speed Roadranger instead.  This tranny will be about 1.75 inches longer than what you have.  Dunno if it will fit however.  Same type large, flat gear box, but with very close gears.  Perfect for that "318"...some say they were made for each other way back when.  HB of CJ (old coot) Smiley
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