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Originally Posted by Maddog
Okay, here’s the gist. I’m actually a writer and im doing this for research. Maybe one day I’ll get around to converting my own Skoolie — my mom and I really want one.
Anyways, so the story centres around a bus. The first portion of the story is fixing it and converting it and other shtuff.
The bus in the story is a 1983 GMC (I think most buses are Bluebirds based on Google searches), but I can easily change stuff. It’s not set in stone. But I think most had gas engines (I was reading through this site but figured it would be easier for me to make my own post).
I was going to make it a diesel, manual with air brakes. Do they even have airbrakes? I can take that out too if need be.
Anyways, the bus has engine and tranny problems, so says the mechanic. Head gasket is leaking really bad, engine sounds tired. Tranny shifts horribly.
How easy of a fix is any of that? How pricey? Is it expensive to do an engine swap, if need be?
Pls help this desperate writer ! Thank you ��
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First and foremost, hi from a fellow writer! (Debut work was "Lucky Number Thirteen" under the pen name Colyer Jameson).
Depends on the '83 GMC, and whether we are talking about a skoolie here, or a transit bus. There were also cutaways just like there are today. But since you're here, that says skoolie.
Another member mentioned the 366/427 tall-deck big-block V-8 that was common in these, but these engines are damn near bulletproof, so while it may be possible to kill one of these tall-deck engines, you'd have to do something extremely stupid, they were actually industrial engines adapted to highway use, something GM did often back then.
I was riding one that couldn't have been any newer than 1972 to school in 1994, with only a puff of oil smoke from valve seals when shifting. Our county still had at least 30 of these in 1994. I even remember the first school bus I ever rode being one of the old Dodges.
But I digress. Since you mention air brakes, diesel, tranny problems, engine problems, specifically head gasket, the perfect scenario for an '83 GMC to have such problems, would be an 8.2 Detroit with an AT545 trans, and such a bus could have air brakes. All were available in the '83 GMC 5500/6500/7500 series back then. The AT545 is a base Allison automatic, which were becoming a bit more common back then.
However, the AT545 Allison is an automatic, which would require some adjustment in your story, but most manual boxes in these were Spicer granny-low 4-speeds, and very tough. I don't remember ever hearing of one lunching a tranny. I suppose the clutch could go out, but for reasons that will soon be clear, you'd have to be extremely stupid to overspeed an 8.2 simply trying to move with a bad clutch. So the AT545 lends itself to this better, methinks, and with a lot more believable cause.
As for how the problem occurred, too low an axle gear ratio with too high a highway cruising speed. 8.2s are known for head and gasket issues, and the AT545 will overheat and burn up or puke if pushed too hard. Most school buses are geared low and not meant for interstate cruising, especially at today's speeds.
An 8.2's RPM range is fairly high for a diesel, in marine applications they are said to run best at about 2300-2500 rpm, and some are set to run as high as 3200. A marine application will typically use internals that allow a bit more RPM, so I would say a highway version (these were essentially marine/industrial engines adapted to highway use) would likely be in the danger zone at around 2400-2600, and most comfortable at around 2100, similar to the Navistar 7.3 / T444(E).
An 8.2 Detroit running 65 mph with a 6.13 rear gear (common in these) and an AT545 Allison would be pushing 3500-3700 rpm, depending on the tire height (most tires of that type these days are about 37 inches tall). And 3500-3700 rpm would certainly fry any 8.2, as well as an AT545, it cannot take the heat and would burn up fairly quickly, especially if the fluid hadn't been changed in awhile.
So that opens up a few foreshadowing options, as well as the mechanic knowing the driver doesn't know beans about what they're doing, or any passengers saying, "See? I told you you were pushing it too hard." That sort of thing...
Anyway, 8.2 Detroit Diesel, Allison AT545 trans, 5.29 / 6.13 rear axle gear ratio, 65 mph... It will overheat the 8.2 and AT545, fry the AT545 in short order, and blow the 8.2's head gaskets, which are all common and believable failures in that scenario.
The 8.2 is also a quirky beast -- its fuel pincher system makes its exhaust stink to high heaven, and it is also getting harder to find replacement engines or parts for them. Also, most diesel mechanics today do not understand them, as they are becoming increasingly rare, but vehicles with them can be bought for a song, owing to the exhaust smell.
As for fixing, replacement would be easier on both counts. The 8.2 isn't an easy beastie to find these days, but let's suppose the mechanic has a wrecked or abandoned truck or bus sitting around the back 40 that has an 8.2 and AT545 trans (these were common in GM medium duty chassis, which were the basis for many a school bus, box truck and medium-duty wrecker back then).
Of course, being that the 8.2 is pure mechanical, perhaps something better could be swapped in its place. Maybe even a different engine/trans combo swap, say a 7.3 / DT408 / DT466 / DT530 Navistar with an MT643 Allison? I suppose the 8.2's head gaskets could be replaced in a day or so, but there's no guarantee that 3200-3500 rpm won't do other internal damage, and there's still the overheated and fried transmission. Might also have the mechanic suggest swapping for the donor vehicle's rear axle for higher gearing (3.91-4.11-4.33), or a 2-speed rear axle (perhaps the bus already has one and the driver didn't shift it to high range, causing the failure at a much lower speed).
Coachwork options back in '83 included Thomas, Carpenter, Ward and Blue Bird, as far as I know. Superior may have still been in business in '83. Others may chime in on this.
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