Considering a Bus Purchase

[luvrbus]

99 % of the time a series 60 will require block work like on the deck and the center bores,then you have gaskets and seals the engine needs to be out to replace,the lower end doesn't give much trouble those things can go a million miles on a set of bearings unless they are run low of oil.DD has 3 levels of rebuild on the series 60 

[chessie4905]

Then the bull gear lets go after a rebuild....

[windtrader]

I'm a low hour guy so forgive my ignorance. My coach 8V71 never picks up speed once on a fairly steep incline. Every 1 MPG  lost for whatever reason is lost until over the crest. The driver/mechanic I got the bus from told me when you see a hill coming up, mash the pedal and keep it there, period. Been good advice so far, just need to watch the temp creep on some of them long grades. Always make it sooner or later. lol

[luvrbus]

I'm a low hour guy so forgive my ignorance. My coach 8V71 never picks up speed once on a fairly steep incline. Every 1 MPG  lost for whatever reason is lost until over the crest. The driver/mechanic I got the bus from told me when you see a hill coming up, mash the pedal and keep it there, period. Been good advice so far, just need to watch the temp creep on some of them long grades. Always make it sooner or later. lol

Nope when you push the peddle and you don't pickup speed you are lugging the engine, catch you another gear or you will pay later like the old Fram filter commercial ,that is bad advice Don   

[eagle19952]

Nope when you push the peddle and you don't pickup speed you are lugging the engine, catch you another gear or you will pay later like the old Fram filter commercial ,that is bad advice Don   

When i see a hill, in 4th gear, I put the selector in 2.
Allison shifts better all by itself and does a better job than me.
In fact I don't need to see a hill.

[mmanning]

What is lugging?  What is happening to your engine while lugging?

Edit:

I think I found a pretty good answer: https://youtu.be/soJea7xEt-8

[windtrader]

Clifford, forgot to add the downshifting part. Yes, mash it until the bus falls down into the next lower gear range, then change to lower gear to keep RPMs up. On steep grades it's still a losing battle for speed in that the bus doesn't go faster but hopefully holds the speed or slows down more slowly until another downshift is necessary.

[richard5933]

I do it by RJ's article on shifting. I approach the hill at speed, if possible, and hold the pedal steady. As the speed drops from 65mph down to 60 mph I get ready to shift. Once the speed is at 55mp (which is 5 mph above my shift point) I initiate the shift from 4th to 3rd gear. By the time I'm done with the shift and ready to let the clutch pedal up my speed is just under 50 mph and we're good to go continuing the climb.

My engine is still fairly new (44K original miles) so probably a bit tighter than most. I feel like it has pretty good power but it will lose speed on grades if they are long and/or steeper than about 3.5%

[Jon]

Wow.........I never knew our buses would slow down on hills.

Don, a long time ago someone said to drive it like you stole it and I think that is good advice. Keeping the revs up is important, not only because you aren't lugging the engine, but because it is keeping the fan moving at a higher speed to help cooling. When I approach steep hills in my bus that is set up to run at lower RPMs than most 2 strokes, I still drop a gear before the bottom of the hill I am about to climb and I pick up some speed to help me carry up the hill.

But your remark about having to watch temps is a strong signal you need to address what is a problem. A healthy cooling system is going show higher temps when the engine is working hard such as a hill  climb, but those temps should peak at some level far below temps that are too high. I don't know your engine, but I would consider the engine and cooling system in good operating order if it ran at a normal 180 for example, but never went past 195 on the steepest, longest hills on the hottest days. Those are numbers I saw on my 8V92 so yours might be different.

[neoneddy]

@manning , yeah I've learned the hard way.  When the going gets tough, gear down and mash that pedal down.  What I missed in the "Don't lug speech" was keeping the RPM up means putting the pedal down even in the face of rising temps.  Your temp gauge will always read 10-15 seconds behind reality.

@windtrader https://www.busconversionmagazine.com/forum/index.php?topic=11957.0  This topic has the chart for the 8v71.   The reason to mash the pedal down is to get the HP up.  Ideally into the 1700-1800+ range.    Like I said earlier, I've noticed I can pull a hill (small MN type hills) at 65+mph pedal down no problem (with the 6v92 TA , turbo helping a ton at 15+lbs boost) But at 55 or even 60, nope not gonna happen, RPMs are just too low and boost is too low to keep it there, so it falls until I need to gear down.

Edit: I noticed your comment on keeping the pedal down until it naturally downshifts.  I don't know on the 8v71, but the 6v92TA that's a bad idea in my experience.  The turbo will by that time generating a tremendous amount of boost in part because the RPMS are low, so the engine can't take in the charge as much.  Anyway, this prolongs the situation of lugging, I find I'm better off accepting my fate  when I see my speed dropping past 60, down shifting and letting up then getting back on it.
These are funny beasts for sure.

[Jim Blackwood]

Then the bull gear lets go after a rebuild....

So what is the cause of that exactly? I've seen it happen, heard about it, there must be a cause and indications, and why would preventing it be something the block must be removed to do?

Jim

[luvrbus]

The engine dosen't need to come out to do the PM on the bull gear when it fails it is common practice to remove the engine and do a complete rebuild because of unknown damage caused,and some do patch one up and go down the road for another 100,000 miles
   

[Jim Blackwood]

But why does it fail in the first place? They must have that information. Is it a million mile wear issue so somebody neglected the replacement interval?  I've got to think that the crank-BG backlash has to be the most critical with BG-cam being next and the others of lesser importance. If it was alignment it would never make that first 1/2MM. So that doesn't sound like it'd have anything to do with the block.

Jim

[luvrbus]

But why does it fail in the first place? They must have that information. Is it a million mile wear issue so somebody neglected the replacement interval?  I've got to think that the crank-BG backlash has to be the most critical with BG-cam being next and the others of lesser importance. If it was alignment it would never make that first 1/2MM. So that doesn't sound like it'd have anything to do with the block.

Jim

You need to ask Detroit that question I just follow the flow sheet they provide for checking the blocks after a bull gear failure,those blocks are so thin and light weight some times you cannot even salvage the block

[Geoff]

The bull gear bearings on Series 60 are supposed to be checked at 750,000 miles for looseness.  The word is if you have any metal in your oil before that the bull gear is at the top of the diagnostic check.  It reminds me of the idler gear bearings in the 2-stroke 71-92 series-- you never know when one could fail and in-frames do not replace those bearings.  Checking your oil for metal in either engine during an oil change is very important to avoid catastrophic failures.