Hi all,
After some absence from the board I'm back with some questions about my MC-8 differential gearing. Since the engine swap to the 8v92 I'm now running up against the governor, 2100 rpm at 70mph. The way the gearing is now the trucks that pass me on the flat I have to re pass on the hills. Anyway from what I have read in doing a search in prior posts about this subject my 8 has a 3.70 gear and would like to get a higher ratio, somewhere in the 3.30 range. My parts manual only lists a 3.70 and 4.11 ratios available even though I find discussion on the boards of the existence of higher gears. I guess my question is a source for a used 3rd member in the desired ratio, or if it is possible to find a new ring and pinion for my 3rd member will the higher gear ratios fit my ring gear carrier. I know on so many rear ends if you change the ratio too much you also have to change the ring gear carrier to match the new gear. Thanks in advance, Mike.
I got my 3:36 ring gear,pinion and carrier from Pro/Gear in Orlando FL for my MCI 8 when I went to the 8v92 .Then I was told later the MCI 9 pumpkin with the 3:36 gear was a direct bolt in for the 8 with a 3:70 pumpkin
Thank you, that gives me a place to start.
I swapped 4;11 to 3:36 gear ratio in my 5C. Best thing I have done to this bus. A 5C is the same bus as an 8, without the drop box, and 5 feet shorter of course. I have the Allison HT740 that has the 1 to 1 ratio in top gear. At 65 mph, the revs are about 1800 rpm. Top speed is 80 mph in 4th, 55 in 3rd, 40 in 2nd. The loss of power is negligible, more than made up by the higher speeds in each gear. And start ability is not an issue with the Allison automatic. I found the gears at a charter outfit in Alberta that has kept every bus they ever used for the past 40 years. Swapping those gears is heavy work. I used a transmission jack, along with other bottle jacks, and some strong language. You have to raise the bus high enough to get the gears slid under it. Higher than you would think. I seem to remember in and out in 2 days. Well worth it.
JC
PS: 11R24.5 tires
I like the 5C bus, if I had not already had the 8 I would have gone for the 35footer. One of the Saudi buses would have been great for me out here in the desert with the double roof they had.
I run the same tires and trans as you. Did you replace the whole pumpkin? And what was it from it that was the case? Having the ability go run 80 if need be would be great. Limited to 70 you just don't have enough extra speed to pass safely at times.
I know it will be a heavy, dirty job but I agree it will be well worth the effort.
Thanks for the input, Mike.
CK with B-K I think he has a couple MCI's he is parting out.
Who is B-K? Thank you, Mike.
Also check with Luke. Or maybe the place near Danville, Pa. on I-80; he has several MCI'S. That's if you have no luck out there.
Mike, I swapped the gears inside the pumpkin. First, drain the oil, pull the axles out, then with the cover off, slide the gears off. Putting the new gears in is tricky, because they have to be slid in just right: level and straight. I had borrowed a transmission jack that adjusts not only for height, but also for sideways and fore/aft level. It is not difficult, but the parts are heavy, and you are working under the bus...
BK is Bryce Gaston. He posts here occasionally. He owns a charter bus company in Tennessee, or somewhere back East.
JC
Quote from: MC8Mike on July 04, 2016, 01:25:09 PM
Who is B-K? Thank you, Mike.
Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
http://www.busconversions.com/bbs/index.php?action=profile;u=8 (http://www.busconversions.com/bbs/index.php?action=profile;u=8)
http://www.kylakesidetravel.net/ (http://www.kylakesidetravel.net/)
check your messages
I spoke with Mike for a moment today and I am going to see if either of the MCI's I still have has the right ratio for him. ( ::)sorry Mike didn't get it checked today, but will in the morning just before I start working on putting my bike back together! I promise bus before bike ~ this time anyway! :P)
;D BK ;D
Course another way is to swap in an Allison B500 transmission. Same 1st four gears of the HT740, but with a .74 and .64 overdrive. Then you don't have to fool with the rear end. Good Luck, TomC
Yeah that is a consideration but I already have a bunch of bucks in my rebuilt ht740. In hindsight that may have been a better option for me. Thanks, Mike.
Even going with the B500 you would need to change the gear ratio to a lower gear for the overdrives
when I installed my b500 I didn't change the gears. if I have a head wind while driving around 60-65 mph I simply put it in 5th gear any thing other I run it in 6th. best thing I ever did
Quote from: c-coop on July 06, 2016, 03:19:21 PM
when I installed my b500 I didn't change the gears. if I have a head wind while driving around 60-65 mph I simply put it in 5th gear any thing other I run it in 6th. best thing I ever did
I have friends that tried too use a B500 with 3:70 it drives you nuts pulling a trailer most of those have been changed over to 4:11 to stop the gear hunting and they are getting better fuel mileage with more power in the hills at a faster speed behind a series 60
I still have the 4:11 gears on a pallet off my 5C if anyone is interested.
JC
you still have the gears , they the same for a 8 ? how much you want for them
I have a rear from a MCI 12 with 4:11 gears and as set of gears from a 102C3 that are 3:33 for sale. (Chep-Chep)
Jack
I don't know if my 4.11 gears out of a 5C would fit in the rear end of an 8. A 5C and an 8 are very similar buses, like identical other than the 8 is 5 feet longer with a tag axle. The 5 has the drop box, but I don't think it would affect the diff gears. Maybe someone else knows if the gears are interchangeable?
Asking $1500.
JC
JC, the pinion gear is different for a dropbox setup fwiw
If he's at 2100 at 70mph, then with the B500, he'll have 1554 in 5th and 1344 in 6th. Cruise at 75 and he'll be at 1665 in 5th and 1441 in 6th. Maybe a bit slow, but running an 8V-92TA around 1500-1700 is perfect rpm for cruising. Good Luck, TomC
Doesn't the B500 have a minimum RPM input speed requirement?
Lubrication issues, that was the challenge as the newer engines are designed to run slower and slower for economy?
happy coaching!
buswarrior
jack you have the whole axle assembly , or just the pig head , anyone know if this will fit in a 8 housing that is for the 4:11
Quote from: buswarrior on January 21, 2017, 09:22:16 AM
Doesn't the B500 have a minimum RPM input speed requirement?
Lubrication issues, that was the challenge as the newer engines are designed to run slower and slower for economy?
happy coaching!
buswarrior
Yes they do but people ignore it and some people get away with it for awhile ;D
The last 4000RDS (B500 with PTO for trucks) I drove, on partial throttle, it up shifted at 1,500 and didn't down shift until 1,000rpm-from the factory. Good Luck, TomC
Quote from: artglass on January 21, 2017, 05:28:41 PM
jack you have the whole axle assembly , or just the pig head , anyone know if this will fit in a 8 housing that is for the 4:11
I have the head, MCI may be able to tell you if it will fit. Model C 3121F1800
Jack
Quote from: TomC on January 21, 2017, 10:59:20 PM
The last 4000RDS (B500 with PTO for trucks) I drove, on partial throttle, it up shifted at 1,500 and didn't down shift until 1,000rpm-from the factory. Good Luck, TomC
There is a difference between the 4000 series and the B500 the "B" is a bus only transmission it is a $3500.00 upgrade from a 4000 in a Prevost fwiw,plus that Allison is a 5th generation it tells the engine what is needed
Mainly low profile oil pan.
The latest Allison in a new Prevost H3 45, Volvo engine, regularly see the tach at 1000 rpm, 1100 rpm, 1200 rpm.
Busnuts need to be painfully aware that an older B500 can't/shouldn't be operated like these new ones...
As usual, there's more to the story...
happy coaching!
buswarrior
Quote from: TomC on January 22, 2017, 06:36:53 AM
Mainly low profile oil pan.
The 4000MH has the low profile oil pan
I'm the first to admit the entire gear ratio issue is one I know little about. But I am confused by a few comments related to top speed.
I don't have the 8v92, but I do have the HT740. When I'm on the highway, (I-95 especially) and listening to AC/DC, I can EASILY get to 90MPH before I even notice the speedometer. The engine runs beautifully and I've never had a temperature issue. How is this possible?
Please note: I do indeed pay very close attention to driving, and ALWAYS know the location of every vehicle sharing the road with me. Those of you familiar with I-95 will understand :)
Quote from: daddysgirl on January 22, 2017, 08:58:40 AM
I'm the first to admit the entire gear ratio issue is one I know little about. But I am confused by a few comments related to top speed.
I don't have the 8v92, but I do have the HT740. When I'm on the highway, (I-95 especially) and listening to AC/DC, I can EASILY get to 90MPH before I even notice the speedometer. The engine runs beautifully and I've never had a temperature issue. How is this possible?
Please note: I do indeed pay very close attention to driving, and ALWAYS know the location of every vehicle sharing the road with me. Those of you familiar with I-95 will understand :)
Better check your speedometer the MCI 8 had 3:73 gears with 12r 22.5 tires and the 740 is is a 1:1 ratio 90 mph is a little fast for that setup
I don't doubt you at all. But I wasn't relying on the speedo. I was going to Fredricksburg for the yearly, and a friend was behind me. He called me and asked me if I wanted a ticket for going 92 MPH. He was pulling his BMW K1200LT and called because he couldn't keep up with his trailer on his F-150.
I looked at the speedo and it was buried (only goes to 85). RPM's weren't in the red either?
BIT... My father was VERY particular about power and speed. He spent his career dealing with diesel engines. Is it possible, when he ordered the engine, that he ordered a different setup? The engine number is "customer specific"...I do not know what he did when he placed the order.
"gear limited" would be the phrase. 70 mph is 2100 rpm through an HT740 and 3.73 differential with 12R 22 tires or close equivalent.
2300 rpm - 77 mph
2500 rpm - 84 mph
2700 rpm - 90 mph
I think those governor settings might be labeled "battle"...
Not recommended for the faint of heart, or the light of wallet.
happy coaching!
buswarrior
All Detroit's are customer specific,if you have a 7 as the 1st number of the last 4 numbers it is a basic engine