do buses always drive like wild broncos?

[druidwood]

Just brought home my Bluebird 1991 TCF (27 foot) and what a wild and frightening drive. Every bump and dip in the road grabbed the wheels and gave me a sense of no control of steering. My rear pilot driver didn't notice it lurching, but from inside if felt like a wild ride. Is this normal? Or is it a sign that something is wrong with tires, alignment, shocks? The tires look very worn by car standards, but as it was being run by a school district perhaps bus tires are different?

Looking forward to tearing out the seats and starting conversion, but hoping once done I can fix the ride to be a bit more controlled. It is also alarming how much gas it needs to go up a hill and then how it takes off going downhill. Did not downshift automatic as I didn't know if you can do that in a bus. I do it in my car, but it doesn't slow it down much. So sounds like exhaust brake would be worth the money - anyone get one installed, and if so what did you think? Safer?

Rank newbie here.

[87mackd]

Speaking for myself of course, the first time I drove my bus I was actually quite surprised how well it handled (87 Blue bird International FE) for how big of a vehicle it is. My tires were pretty worn too and have since been replaced, What your experiencing sounds like new shocks and possibly tires would help. Tires on your bus are extremely important. especially the fronts. Wouldn't worry about alignment unless your experiencing pull to one side or the other or experiencing excessive vibration in the steering wheel. Changing my front tires improved almost every part of my driving comfort.. start saving now ha.

As to the exhaust brake.. I recently looked into this myself. Your going to want to do some research into your transmission type. I have the AT545 which many on this site will tell you has no lock up torque converter. If that means nothing to you, know that it is the reason your bus might scream down a hill no matter what gear it is in. This is due to the lack of lockup torque converter. This LUTQ converts most of the power from the engine to the trans, without it the torque converter does what its able to do but no more. I'm not sure (and curious to see what others write) but I believe a exaust brake or jake brake (there is a difference) would just slow your motor down and that would not be transferred to the transmission due to the lack of the Lock up torque converter.

[2kool4skool]

No, they shouldn't.

I would:
Check tire pressures, our '00 TC of the same size is happiest (for our wt.) with 100 front and 85 rear.
I replaced our shocks, the fronts made the biggest difference. It was bouncing quite a bit over dips.
Perhaps there too much play in the steering. That can add to the problem.
Wheel alignment.


http://www.skoolie.net/forums/f13/ho...tml#post194039

[Iceni John]

To answer your question - no! However, short-wheelbase buses will always have a choppier ride than longer-wheelbase buses, and front-engine buses usually don't ride as smoothly as pushers or mid-engine buses, especially in the back.

The only supplementary brake that will work well with a non-lockup transmission is a Telma retarder. There are two versions: one attaches to the driveshaft, and the other to the rear axle. Telmas work very well, but you will need a large alternator and batteries to power their field windings. Engine exhaust brakes are not as effective as engine compression-release brakes such as Jakes, but without a lockup torque converter or a manual transmission neither will do much anyway.

John

[druidwood]

Thanks to everyone for the information. I did not know about the torque converter - have to look up which Allison transmission I have. I bought it from a diesel mechanic who suggested the exhaust brake, but goes to show you there is a lot to know. According to rv blogs it sounds like I could upgrade the transmission and get a retarder. Had my brakes fade once going down a huge grade pulling a trailer (Uhaul, no brakes) and did not appreciate what the extra weight was doing. Luckily happened to pull into a rest stop when I realized and got it slowed enough to bump into the curb - BUT a scare like that stays with you, so am concerned about this bus screaming down the huge passes out here - the truck escapes all look well used on Willamette Pass. Will get tires replaced and shocks checked once I get bus on the road and hope for a smoother drive.

[cadillackid]

what you experienced is bump steer.. new heavy duty shocks and proper tire inflation is important.. too little and you'll risk over heated tires.. too much and your ride is very harsh.. bump steer can also be caused by loose steering components.. school bus steering boxes are notorious for falling out of adjustment, and or needing alignment..

on large bumps or freeways where there are a lot of messed up pot-hole patches you'll still get some bangs and bump steer.. prevalent esp in areas where road quality isbad due to salt or ill maintained roads.. my trips south in both my busses tend to yield that ocne I get into southern kentucky and on southward that my ride will be much smoother than when i was in the northern states...

-Christopher

[bigskypc50]

My bus is a bumpy rough but well controlled drive, I too was surprised how well they handled, I was expecting something between a tank and a rock but not at all the case.

I had older 73 Dodge Class C with a messed up steering box and it drove like what you talking about. Super loose steering on bumps I have to drive it like they do in the movies back and forth bank and forth all the time, Scary ride! I agree check your steering box and tires.

[Iceni John]

A transmission retarder can seriously overheat and damage your transmission in a hurry if you use it down long mountain grades. At the very least you'll need a supplementary transmission cooler (a BIG one) and an accurate transmission temperature gauge. That's why Jakes and Telmas are used by big trucks - they can be used continuously without any risk of overheating or damage.

John

[Brad_SwiftFur]

As a professional driver and having been driving large vehicles for years, I'd say no. That sort of lack of control is not normal for any vehicle. Front tires need to be at 90 PSI minimum, the rears no less than 85. With the engine off and safely parked, check to see how much play is in the steering.

Shocks should help and taking up any play in the steering will help tremendously. Alignments are rarely done on these big vehicles and usually only done if it pulls to one side (and after checking other things such as tire pressure, wheel bearings, and brakes), or it's wearing the tires unevenly (which could also be cause by kingpin bushing wear, a fairly common issue).

[cowlitzcoach]

The short wheelbase Type 'D' FE buses tend to hop from expansion joint to expansion joint when going down the road. If the expansion joints are at just the wrong spacing the bus can almost feel like a bucking bronco until you slow down some.

As far as corralling it while going down the road, if the shocks are dead (not unusual on any school bus more than 10-years old) that will make a huge difference. If there is any slop in the king pins, drag link, tie rod ends or steering box you are going to have a hard time keeping it between the lines.

But when everything is in good condition and adjusted properly you should be able to sit back and drive with one hand on the wheel and not need two hands of white knuckles holding on for dear life.

The AT545 gets a bad rap because it isn't what the MT643 or MD3060 are. But for what it is the AT545 is a very solid transmission that can go 500K miles with nothing more than regular service. The key is you don't want to get it hot. Heat will destroy it in no time at all. If your bus does not have a transmission temperature gauge that needs to be one of your very first purchases and installations. The second thing you are most probably going to need is more transmission cooling. Unless they were ordered new from the factory with additional transmission cooling the "stock" cooling loop is barely adequate when running around town on the flats. Put it on a hill and you can peg out the temp gauge in next to no time at all with the bus empty.

As far as going down a grade, if you understand what you have you shouldn't ever have any problems. In September 1990 I was assigned a brand new Blue Bird TC2000 with a Cummins 5.9L/Allison AT545. The first time I drove the bus on my route I drove it up and down the hill the same way I had done the previous four years in a Loadstar/Thomas with an MV404/Allison AT545. Going up the hill was like I had a rocket under my tail compared to the Loadstar. Going down the hill I downshifted into 2nd like I had done in the Loadstar and discovered the AT545 behind a diesel engine does not hold back on a downgrade the same as the AT545 behind a gas engine. To say I was standing on the brakes and smoking them is an understatement! I learned that when going down anything steep if you want to stay under 35 MPH I needed to lock it down into 1st gear. I also learned that the transmission cooling loop was woefully inadequate for climbing a hill on the upgrade and the brakes were barely adequate for slowing down on the downgrade.

All ten of those TC2000's we got that year spent time at the dealer getting upfitted with huge transmission coolers and swapping out the rear brake cans to 30/30 cans from the 24/24 cans that came from the factory. Those buses may have worked in an urban/suburban setting in a flat locale but were not at all ready to work rural/suburban with big hills.

The next batch of TC2000's we got in 1993 came with 20 more HP, MT643 transmissions, radiator shutters, and bigger brakes.

All of that is to say that once you get your bus dialed in it should be a joy to drive and easier to drive than a mini-van.

Good luck and happy trails to you!

[druidwood]

Thank you, lots of good info. It does have a transmission temp gauge and it read 220 all the way home, which was city/freeway driving but no hills. That seems high considering it is empty and had no hills. So I will test out driving it down some hills and putting it in 1, 2 and 3 (it is an automatic) and see if it helps, though suspect that like my car it will just force me to brake to keep the rpm's down. Good to know re: brake canisters as well and I will see if the current ones say which size they are. This might not be the bus for me, but one tries to research and then make a decision THEN the learning begins.

[druidwood]

Thanks John. As you seem to know about this, if I replaced the transmission at some point with one that has a torque converter, would downshifting then actually slow the bus without the need for auxiliary braking? Would an exhaust brake on a transmission with a torque converter still require a cooler?

[turf]

yes, any other trans with a locking torque converter will help hold you back on hills. the 545 manual says just to use the service brake to control speed.

a locking TC will run cooler on hills since the is no slippage when its locked up. as you head up a hill with a non locking TC, you rpms stay pegged out, but your speed drops. that difference is dissipated in heat. a locked TC will slow when the rpms slow.

i didnt read every word above, so maybe i missed it. but if my bus was lucy goosey in the steering, the first thing i'd do is jack up each front wheel and check bearings and kingpins.