Author Topic: Cummins ISM Repower  (Read 690 times)

Offline buswarrior

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Re: Cummins ISM Repower
« Reply #15 on: March 15, 2019, 05:39:47 PM »
Something wrong in these numbers.

6 cylinders in a row vs 3 cylinders in a row...

Confirm sources over and over, the internet is total $#!% when it comes to this info...

When I type $#!%, I'd like it to say $HIT...

happy coaching!
buswarrior
« Last Edit: March 15, 2019, 05:41:45 PM by buswarrior »
Frozen North, Greater Toronto Area

Offline Jcparmley

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Re: Cummins ISM Repower
« Reply #16 on: March 15, 2019, 05:44:30 PM »
Is there a site that has these specs that is trust worthy?  I don't have a manual with me so the internet is all i have at the moment. 

Something wrong in these numbers.

6 cylinders in a row vs 3 cylinders in a row...

Confirm sources over and over, the internet is total $#!% when it comes to this info...

When I type $#!%, I'd like it to say $HIT...

happy coaching!
buswarrior

Offline chessie4905

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Re: Cummins ISM Repower
« Reply #17 on: March 16, 2019, 04:03:12 AM »
At least you can verify your coach with a tape measure. Also the listed length from the attachment on the transmission supplied may or may not include the additional length of an output shaft flange or yoke for driveshaft attachment. Personally, I'd go somewhere to actually measure one before going ahead on the purchase. Also you need the center to center measurement of u-joint caps on your driveshaft to get an accurate length. Also check if you will have any room to shift new engine closer to rear bumper, if necessary.
GMC h8h 649#028 (4905)
Pennsylvania-central

Offline TomC

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Re: Cummins ISM Repower
« Reply #18 on: March 16, 2019, 05:58:03 AM »
I know a couple of bus people with this combo in the 102C3 and it works great! The nice thing about the HD4060 is the first four gears are just about identical ratio wise to the HT740. And the fact that the ISM can put out more torque than the 6V-92TA (1550lb/ft in RV form), I don't believe you'd have to switch out the rear end ratio.
For sake of discussion-if you have 12R-22.5 that's a 485rpm tire. So with your 3.36 rear end, at 60 you'll turn 1629rpm. At 70 you'll be at 1901rpm and at 75 you'll be at 2037rpm. 5th gear is a .74 overdrive. At 60 you'll turn 1205, at 70 you'll be at 1409, and 75 at 1507. You want to be somewhere between 1400 and 1800 cruising with the Cummins ISM-so nothing wrong with using 3.36-you'll just not be able to drop into 6th till 80. At 2100 in 6th (.64 overdrive) you'll be going 121mph (you won't have enough horsepower to go that fast). But at 80 in 6th you'll be at 1390-probably again not enough horsepower. But there is nothing wrong with blocking 6th gear out-it's just a programming issue. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline buswarrior

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Re: Cummins ISM Repower
« Reply #19 on: March 16, 2019, 06:08:08 AM »
Tom, would one even need to bother locking out 6th in this scenario?

Conditions for an upshift would likely never be met, so just ignore it? Save a dollar?

Happy coaching!
Buswarrior
Frozen North, Greater Toronto Area

Offline Jcparmley

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Re: Cummins ISM Repower
« Reply #20 on: March 16, 2019, 12:19:11 PM »
Tom, would you recomend I do this repower or should I have my 6v92ta rebuilt? 

I know a couple of bus people with this combo in the 102C3 and it works great! The nice thing about the HD4060 is the first four gears are just about identical ratio wise to the HT740. And the fact that the ISM can put out more torque than the 6V-92TA (1550lb/ft in RV form), I don't believe you'd have to switch out the rear end ratio.
For sake of discussion-if you have 12R-22.5 that's a 485rpm tire. So with your 3.36 rear end, at 60 you'll turn 1629rpm. At 70 you'll be at 1901rpm and at 75 you'll be at 2037rpm. 5th gear is a .74 overdrive. At 60 you'll turn 1205, at 70 you'll be at 1409, and 75 at 1507. You want to be somewhere between 1400 and 1800 cruising with the Cummins ISM-so nothing wrong with using 3.36-you'll just not be able to drop into 6th till 80. At 2100 in 6th (.64 overdrive) you'll be going 121mph (you won't have enough horsepower to go that fast). But at 80 in 6th you'll be at 1390-probably again not enough horsepower. But there is nothing wrong with blocking 6th gear out-it's just a programming issue. Good Luck, TomC

Offline lostagain

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Re: Cummins ISM Repower
« Reply #21 on: March 16, 2019, 12:46:59 PM »
I have a 6V92TA with HT740 in my bus now. 9G90 injectors, TV 7512 turbo, 3.36 rear, 24.5 tires. That gives me 350 HP and 1050 lb/ft of torque. It goes down the road quite nicely. It is a very reliable engine. Doesn't leak, doesn't burn oil. Has taken us from coast to coast, and Mex to Canada, and everywhere in between, without a hiccup. If and when it shits the bed, I would probably rebuild it and get another life out of it. Simple to work on, parts still available, mechanical without electronics. A repower with a different engine/transmission would be an enormous amount of work and more money than rebuilding the 6V92. 

JC
« Last Edit: March 16, 2019, 12:48:47 PM by lostagain »
JC
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1977 MC5C, 6V92/HT740

Offline TomC

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Re: Cummins ISM Repower
« Reply #22 on: March 16, 2019, 01:28:33 PM »
If the transmission is already programmed for 6 speeds, then nothing else needs to be done. The transmission will only shift into 6th when appropriate, and will down shift as necessary. If you get a hunting situation between 5th and 6th, simply push the down arrow to hold it into 5th-done!
I would also just rebuild the 6V-92TA. Parts are going to be around for a long time-only thing is finding suitable mechanics that can work on them. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline luvrbus

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Re: Cummins ISM Repower
« Reply #23 on: March 16, 2019, 02:24:53 PM »
That setup from the Gulfstream was using 4:56 gears some were as low as 5:30 using a 3:33 or 3:36  gear you lock out 5 gear too all of that is explained in the Principals of Operation Manual go the World Transmissions surely I am not the only person on this board with the Principal of Operation Manual for Allison.The 6v92TA is 41 inches long they are measured 2 ways the 44 inches is a fan to fly wheel measurement,the 6v92TA is 1 inch longer than a 6v71 which is 40 inches long.You need to check the ratio on the transmission it comes in a close ratio and a wide ratio Allison can do that for you with the model and serial number don't bank on it being the same as your 740 in the first 4 gears     
« Last Edit: March 16, 2019, 02:56:33 PM by luvrbus »
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Offline chessie4905

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Re: Cummins ISM Repower
« Reply #24 on: March 16, 2019, 03:35:39 PM »
If you lockout 5 th and 6 th, not much point on that transmission unless you add the gear change to the mix...more$$$. Might as well go with the 740 you already have.
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Offline Jcparmley

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Re: Cummins ISM Repower
« Reply #25 on: March 16, 2019, 03:54:39 PM »
I was worried that parts won't be available and that mechanics would soon be hard to find. I am also worried about the cooling issues.  If I do a rebuild I would probably upgrade the radiators.  If I rebuild the 6v92TA MUI what can I do to get the most power?

If the transmission is already programmed for 6 speeds, then nothing else needs to be done. The transmission will only shift into 6th when appropriate, and will down shift as necessary. If you get a hunting situation between 5th and 6th, simply push the down arrow to hold it into 5th-done!
I would also just rebuild the 6V-92TA. Parts are going to be around for a long time-only thing is finding suitable mechanics that can work on them. Good Luck, TomC

Offline buswarrior

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Re: Cummins ISM Repower
« Reply #26 on: March 16, 2019, 07:15:41 PM »
Every Tom, Dick and Harry weren't too good with the Detroits years ago... Nothing changed there.

All those youngsters who were trained by the US military to maintain that fleet of EMP proof vehicles still have lots of life left in them.

Lots of boats, generators and pumps being run by Detroits, and plan to be for a long time.

We may have to look harder for a mechanic, and no doubt, the parts aren't likely to be priced at clearance, but once you have your Detroit up to snuff, when are you ever going to need anything again?

The decision is about your desires, your hobby, what YOU want to do with your coach.

It doesn't have to make sense, it just has to make you happy.

Building a strong 6V92 is just as fun as swapping in an ISM.

Pick yer fun?

Happy coaching!
Buswarrior
Frozen North, Greater Toronto Area

Offline luvrbus

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Re: Cummins ISM Repower
« Reply #27 on: March 16, 2019, 07:34:39 PM »
It's just the shops that don't want to work on a 2 stroke they are geared for the electronic  4 strokes ,the 2 stroke era for hiway use ended in 1997 that was 22 years ago
Life is short drink the good wine first

Offline richard5933

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Re: Cummins ISM Repower
« Reply #28 on: March 16, 2019, 07:42:03 PM »
Interstate in Milwaukee has a few techs trained on 2-strokes. They are also continuing to train apprentices to work on them and last year purchased a few dozen used engines for parts. I imagine that having Lake Michigan next door means that they do quite a bit of marine work, and there are lots of these engines in marine use. In all the times they've worked on my two buses they've never not been able to find what they need through their usual supply chain, and they've never not had qualified techs to work on it whether first or second shift. There is another shop in town that has offered to work on the bus when needed as well. I know that this is just one anecdotal piece of the puzzle, but like has been said with the number of military mechanics and marine mechanics trained on these things I'm not worried.

My only problem has been when I accidentally hit the engine shut down on my first trip home in the bus after buying it. I was at a Flying J and got stuck right in the middle of the main lane - couldn't figure out how to reset the flapper. Clearly my own fault, and if I had read the manual I would have known. I went to the service bay to see if there was someone that could help - someone did finally offer to try and help, but it was clear that they had no 2-stroke people on site.

So, Luvrbus may be correct in that there are some shops that don't have the necessary people on hand, especially those that focus mainly on the trucking industry. But, fortunately there are still many shops around that do.
Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412 (Former Bus)
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Offline kevink1955

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Re: Cummins ISM Repower
« Reply #29 on: March 16, 2019, 07:53:40 PM »
My FD still has 3 pumpers with 6V92 engines, of course they are Ddec. They run great and have never given us any trouble.  Everything else is Series 60,  we have 1  that lost a valve 3 months ago and is still not back in service.