Engine and Transmission combinations

[CrabbyMilton]

I was looking at a 1970's era GMC(CHEVROLET same blasted thing) school bus chassis brochure. I have noticed this and I'm sure that there is one or more reasons for this in that the old 292 6 cylinder engine was not paired with the available ALLISON 540 transmission. If you wanted an automatic back then, you would have had to get the 350 V8 or larger which was by far the more popular engine anyway. So for you powertrain experts out there, could that 292 be bolted up to an ALLISON tranny or was there some reason why it was not. I have a few theories but I'll see what reaction I get first.

[Chopper Scott]

Now your asking questions that I may know something about with the gassers. Chevy bellhousing patterns on the block are the same as far as the older 6 cylinder 230 and 250's versus the 283/327 types. Same goes for the 350. I am basically sure that the 292 is also the same. You could bolt a Powerglide or TurboHydro to any of them. The part you may have some issues with is starter mount and ring gear but I am sure you can find something suitable. The only reason I can see that it was not offered is the power loss an automatic incurs therefore really limiting the 6 cylinder. Thats my story any ways!!

[TomC]

While the Allison 545 sounds good on paper, it is a four speed direct with no torque converter lockup-so it would be very inefficient at freeway speeds.  I would suggest you find a 4 spd overdrive Chevrolet/GMC heavy duty transmissin from a pickup since they have a lockup in both 3rd and 4th-and WAY less expensive if you have to work on it.  Course the most bullet proof transmission would be the TurboHydro 400 3spd-but then again, no torque converter lockup or overdrive. For the amount of money and hastle that you're going to go through, I'd just change the complete engine/transmission to what you want.  I'm sure there are lots of junk yard combos that will satisfy you.  The ultimate would be if you could find a wrecked U-haul truck with the 8.1 liter gasoline and Allison 1000 6spd automatic.  Good Luck, TomC

[CrabbyMilton]

I was thinking of both of those theories. Looking back though, how in the world did those things every do the job with such low power engines. I mean a big V8 with over 250 HP seems taxed enough in one of those let alone 110 HP 6. I'm not looking to buy but I always seemed to have an eye for GM school bus chassis from the early 1960's thru the early 1980's for some reason perhaps some bus exposure from childhood. Ok, I have a guilty pleasure for certain school buses. There I said it.

[artvonne]

I was thinking of both of those theories. Looking back though, how in the world did those things every do the job with such low power engines.

  There is little comparison. The camshafts they used before 1972 have been virtually illegal for highway use since then. Those old sixes had gobs and gobs of low end torque, but didnt rev very high. By 3500 they ran completly out of power, and way back they had splash oiling so any faster would litteraly blow them up. But ease the clutch out at idle and they could pull a barn down. Plus many were real low geared in first, and 50-55 mph on the highway was about all they could do. But they could do that speed pulling almost anything you could hook to them.

[gus]

As art says, the ole 292 is a great engine. I had one in a '74 one ton granny low that would pull tree stumps and haul a heavy load all day - it just wouldn't go faster than about 55mph.

I wouldn't want one in a bus that I was going to do any traveling in!!

It has almost as much torque as the larger V8s but it won't go fast and they will.

HP is speed, torque is work.

[DaveG]

Anyone got a GMC 261 they wanna get rid of? Friend of mine is building a pickup and would like one to build. West coast or Calif would be nice.

[papatony]

Does anyone know the exact clutch and pressure plate to put a roadranger 9 to a 8v71 in a 4501? I have read past threads but did not get a positave answer.

[artvonne]

  I was curious if a fuller 5 speed such as is used in an MCI 9 will fit in an MCI-5 with an 871. I read something that made it sound like it was too wide?

[TedsBUSted]

I was looking at a 1970's era GMC(CHEVROLET same blasted thing) school bus chassis brochure. I have noticed this and I'm sure that there is one or more reasons for this in that the old 292 6 cylinder engine was not paired with the available ALLISON 540 transmission. If you wanted an automatic back then, you would have had to get the 350 V8 or larger which was by far the more popular engine anyway. So for you powertrain experts out there, could that 292 be bolted up to an ALLISON tranny or was there some reason why it was not. I have a few theories but I'll see what reaction I get first.

Put my vote in too, for the 292 being a great engine.

As to bolting up, the 540 has an SAE housing which bolts to whatever engine through an adapter. Since a 292 shares back-of-block dimensions with the eights, a 350 SAE adapter housing could be utilized to bolt up a 540.

However, the 292  used a unique automatic flywheel (flex plate) which was heavier than a v-8 and also used an extra reinforcement at the crankshaft bolt circle. If that wasn't enough, the flywheel was also pinned to the crankshaft with precision reamed dowels. All this extra manufacturing cost was to address the 292's terrific low-end torque, which I would say easily exceeds the 350's potential twist or even the 366 when worked out of its peak range.

If or why the 292 wasn't offered with a 540, I'm not exactly sure. However, most of the  parts required to mate a 292 to a 540 were already in the bin. What theories did you have in mind, CrabbyMilton?

On a related note, while I was running in rewind mode, an F-600 (or so) with 300-6 and beefed-up C-6 did pop out of the mental archive.

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[CrabbyMilton]

Well, perhaps the product line was set up this way and they felt that most buyers at the time just would want the bigger engine with the 540 anyway. Or perhaps ALLISON didn't want to change the gearing in the 540 to work with the 292. I'm sure the old 292 and FORD 300 could have been made to put out similiar HP and torque as the V8's but the V8's did so and were much more accepted so why bother was probably a reason. Everybody has a good perspective on this though.
I still remember in grade school in the 1970's, our school had 2 1960's INTERNATIONAL LOADSTAR 1600's They were almost identical(to a 5-10 year old) except I knew for a fact that one of them had a 6 cylinder gasoline engine and the other had a V8. The one with the 6 really screamed on the freeway. I understand that a 6 in that old LOADSTAR was not that common so that's why I noticed and such engines are etched in my mind even though I prefer a V8 over a 6 in my personal vehicle if possible. Fortunatly, my '04 GRAND MARQUIS never offered a 6.

[luvrbus]

I never saw a 540 mated to a 292 but the turbo 475 was used in the C-50 trucks with a 292 saw few of those before fwiw very tough transmissions had the emergency drum style brake on the tail shaft used a lot in motor homes behind the 454 also behind 366 gaser in trucks



good luck