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75 Coach - Cummins ISC upgrade suggestions
#1
I ran into someone selling a 2003 Gillig Transit Bus motor-transmission-radiator basically this is a frame cut that has been in his building for 5 years. He runs a bus company in Dearborn close to Detroit. From the pictures it looks ok and it's supposed to run and all that stuff. Time will tell.
 
I'm hoping on some sage advice on what to check and what needs to be replaced or serviced. Due to the age and unknown nature I'll be doing an oil analysis first to confirm as much as I can. This is the CAPS Fuel System so it does have some weak area's right off the bat. I'll update the lift pump and will most likely be going through the engine and transmission - it was basically too cheap to pass up. It also has the side mount radiator which should be fun since mine is in the back.
 
Has anyone done the Fass or other upgrades? I don’t Newell had this as an engine option. I have heard of a few Guru’s doing a Cummins 8.3 upgrade on the older units like mine.
 
 My coach currently has a Navstar 9.0 litre out of a school bus that was put in shortly before I bought it three years ago. I've been hoping to find an 8.3 mechanical injection engine - I've seen some, but in most cases either I'd have to buy an $8,000 bus to get one ot it was 3 or 4 states away.
 
I have lots of time to get this right, my coach won't be out till next year in the summer at the earliest plus the old diesel I have now runs great. I'd just like to have something that can get up the hills better and has the capability to engine brake going down. I don't think it has a Jake Brake on it since it was a transit bus. More to come on that if there's any interest.


Thanks in advance - John
John and Marcia Marshall 
1975 Newell 30ft - 9.0 IHC - soon Cummins 8.3 - Allison
IHL 9.0 160hp - picked up a Cummins ISC 240hp
98 Mustang GT
getting closer
ASE Master & Computer Admin
Love old
#2
Look very carefully at the gearing!!!!!! Transit buses are not geared to run at interstate speeds.
Richard and Rhonda Entrekin
99 Newell, 512
Subaru Outback Toad
Inverness, FL (when we're home Cool )
#3
@Retro has repowered 2 70's Newells with Cummins 8.3 mechanical motors and Allison 6 speed transmissions. He would be a great resource for you.

A 2003 Gillig transit bus will have an electronic motor and Dynex multiplex system, and you didn't specify what transmission. From my experience, you'll want to go with an Allison. If you choose to stay with the electronic motor and use a monitoring system, Silverleaf only works with Allison. My donor bus had a ZF, fine transmission but very limited Internet information, and the wiring diagrams I've found are in German. My donor transit bus was from Denver and they make runs to the airport on the interstate, it was easily able to do the 80mph speed limit on I84 in Idaho.

Do you have the ability to do the work yourself? If you're not able to do most of the work yourself, you're looking at a very expensive project.
Jon & Chris Everton
1986 40' Dog House #86
0 hp 8V92 Allison HT740
Soon to be 500 hp ISM 6spd ZF
#4
Thanks Richard - appreciate your insight. As always I think you're correct.
From what I've read online it appears that this does have a limit of 65mph. From talking to the seller he ran these buses in his tour business for a number of year's. I'll check with him, I'm also hoping to buy a set of manuals off him which should help if he's agreeable.

For my coach that speed is probably the limit anyway. When I drove it up from Indianapolis Indiana to Jenison Michigan the sweet spot for speed was about 58 mph when listening to the engine. My guess is this is because of the Carter years 55mph laws. At least that's my guess anyway. I'd bet to improve the top end speed I'd need to change the rear axle gear's. Not impossible, but I'd worry the drum air brakes might not be up to the task for quick stops.

I've never seen a 8.3l ISC engine up close. Just pictures on the internet. It is huge!! and the transmission also is. It's also a 24v system which surprised me a little also. It has the side radiator which if it will fit would be nice. I thought my Navstar 9.0 litre was big - this thing takes it to a whole different level. This is also a full frame cut so everything is there including hundreds of wiring and connections with a number of rear boxes and tubes running everywhere. This has a Voith 5 speed automatic with a retarder - at least it looks like it to me. I'll most likely replace that and go with a Allison 3000 World Transmission before this is done. The overall unit is dirty and greasy - needs a full on cleanup before I get started. The transmission oil and engine oil both look great. I'll be sending in samples in a few weeks to see though.

I'm pretty good with a schematic, but may have bit off more then I can chew. Time will tell. If I can get it setup - tested and running on the frame, I should be able to pull additional information from the ECM. I'm pretty sure my tester will connect.

The more I look at it I think this is a pretty crazy idea, but boy if I can make it work if should get me up and down the hills a lot better then what my current drivetrain can do.

My current setup works so that will be what I try first. At the price I paid for this I don't think I'll be hurt even if I decide to sell it. I like having an upgrade option, however after looking at it I should have gone with a Navstar 466 or a Cummins 5.9 or 6.7. Everything I've read has pointed to the Cummins 8.3l.
Oh well should be interesting.
John and Marcia Marshall 
1975 Newell 30ft - 9.0 IHC - soon Cummins 8.3 - Allison
IHL 9.0 160hp - picked up a Cummins ISC 240hp
98 Mustang GT
getting closer
ASE Master & Computer Admin
Love old
#5
I can do the all the work myself thank goodness - my past career was  ASE Master Auto Technician. I specialized in computer - electrical - wheel alignment and mechanical repair. All the stuff the people that worked for me couldn't or didn't want to do. I also have a pretty complete set of tools and equipment. Most of my stuff is more car and light truck based. Although I have had the opportunity to buy some welding equipment which has been fun and some of the bigger hand tools to work on the wheels and tires.
I'm a want to be gear head - without a hot rod right now. I'm big into older Sun Electric and other testing equipment. My wife and neighbors all call it junk. Eye of the beholding thing.
My careers have not been financially blessed. However I've also made enough to be comfortable here in the Mid-West and have had enough to buy my Junk / Treasures - who could ask for more. Not me!!

I'm a Computer System Engineer now - I work mostly on Windows and VMware Systems for a fairly large Travel Company - thirteen years - I work from home but due to Covid and the current business climate took a pretty large pay cut.
My careers have pretty much been like this all along. I have to say I've had a great time on all my jobs though. I did the Amoco Full Service Dealer thing for 19 years after working in Engineering for 3 year's. I'm one of those old guy's that worked a drafting machine. I'm probably going to retire next fall if my job lasts that long. Right now we live in Michigan - we will most likely end up in the Tulsa area since that's where out grand kids are. Closer to Newell also. My coach is a little out of their wheel house though due to it's age.

Getting this coach going has been fun - frustrating too when you find more work to do but fun none the less. Can't wait to get out there and see this beautiful country.
John and Marcia Marshall 
1975 Newell 30ft - 9.0 IHC - soon Cummins 8.3 - Allison
IHL 9.0 160hp - picked up a Cummins ISC 240hp
98 Mustang GT
getting closer
ASE Master & Computer Admin
Love old
#6
If you decide to buy the 2003 Gillig pieces, I would strongly suggest buying the Cummins Insite/Inline tool. Mine is the Inline 5 which only works on 32 bit XP system, but I have a dedicated laptop for it. Check out http://rawze.com/forums/index.php, great site for tuning your motor. You'll also see links on getting the Chinese copies of Insite to work. Another good source is the Cummins website. Enter your serial number and it'll let you know all the components in your motor. https://quickserve.cummins.com/info/index.html

Another thing that I did, the Cummins quick serve was able to tell me the ECM programming for my 280 hp transit bus. I searched RV ads for coaches that had Cummins ISM motors and found a comparable coach that was rated for 450 hp that had the motor serial number. I added that to quick serve and was able to get the ECM programming information. I also bought the rebuild hardware for the 450 hp motor when I had the motor rebuilt. Head, pistons, and injectors were all different. Cost between $8 and $9k for all the new parts.
Jon & Chris Everton
1986 40' Dog House #86
0 hp 8V92 Allison HT740
Soon to be 500 hp ISM 6spd ZF
#7
Thanks Jon - awesome stuff - wow not sure I'd try to setup with that kind of power. Cool idea's on getting there though.
I love this type of stuff so will enjoy getting into some of the details.
John and Marcia Marshall 
1975 Newell 30ft - 9.0 IHC - soon Cummins 8.3 - Allison
IHL 9.0 160hp - picked up a Cummins ISC 240hp
98 Mustang GT
getting closer
ASE Master & Computer Admin
Love old
#8
I got lucky and found someone selling an 2002 Allison MD3060 transmission out of a Bluebird bus locally. From what I've read, this will be a 5 speed unless I can find a wtec3 ecm with the 6th gear unlocked. It will require some other upgrades to get it working - I'd feel more comfortable using the Allison instead of the Voith Automatic - The only downside is the Voith does have a built in retarder which would have been a nice to have.
John and Marcia Marshall 
1975 Newell 30ft - 9.0 IHC - soon Cummins 8.3 - Allison
IHL 9.0 160hp - picked up a Cummins ISC 240hp
98 Mustang GT
getting closer
ASE Master & Computer Admin
Love old
#9
Check with @Retro, he was able to get the 4spd ECM from a school bus reprogrammed to a 6spd.
Jon & Chris Everton
1986 40' Dog House #86
0 hp 8V92 Allison HT740
Soon to be 500 hp ISM 6spd ZF


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