| Author | Message | ||
| phil potter (216.234.120.211)
Rating: N/A |
I have a MC8 with a 8V71 detoit and manual 4 speed trans. When I bought it. the motor only had 40,000 on a out of frame rebuild. It's second in 5 years. It used tons of oil for me and now I have a craked head or blown gasket. Thinking of giving up on this one and starting fresh. I'm looking at a 6V92 with allison trans ($6,000 for good engine, trans. and everything needed for conversion)or a Military 8v71 rebild with 0 hours -(Normally $4,500 - $6,000 - I may be able to get for $1,800). simple to swap out 8v71 compared to convertion to 6v92 and auto trans.. Will I wish I made the swap? Has anyone ever used a Military rebuilt Detroit? phil | ||
| Nick Morris (Nick3751) (65.117.139.135)
Rating: N/A |
Phil, I've got a friend that works for Cat in GA. He's done several of these and says they're a great deal. The military replaces the engines in the equipment every so many years to keep it reliable and most of the engines didn't have very many hours on them to start with before they were pulled and rebuilt from the ground up all new everything. That's Cat stuff but I'm guessing Detroit does about the same thing. | ||
| Phil Dumpster (24.16.243.37) Rating: N/A |
The 6V92 will use less fuel than the 8V71, but this will be offset by the automatic versus standard transmission. A military rebuilt 8V71 at $1800 is a steal. Many folks who have converted from standard to automatic have regretted it. It's all a matter of personal preference. | ||
| FAST FRED (65.154.177.28) Rating: N/A |
Many of the military engines are tank motors. They have lots of parts located in different places , so mauy or may not require different exhaust ect. Many are turboed and set up for a very high HP , and might not give the service life you hope for IF you put your foot into it too much. Adelmans & other brokers occasionally has then , for lots less than $1800. There a good deal IF you can fit them. FAST FRED | ||
| phil potter (216.234.120.239)
Rating: N/A |
This one is turboed. Will fuel milage be much different with these. I was getting 6mpg with my old one. I'll have all the parts from my old one for the external differences. Is there a different manual trans. that I would like better. Would it be worth putting the 5 speed manual trans in? Much different than the 4 speed? found a 5 speed for $750 who is "Adelmans"? phil | ||
| DonTX/KS (66.82.9.30)
Rating: N/A |
I had one of these, there are far more differences than just the accessories. It came in a 413hp version, they make them left and right rotation. I would forsee many problems down the road, when it came time for new injectors etc, DD dealers seem to wash their hands from them. Remounting the turbo is the least of your problems. If you need the hp and can put up with the difficulties, go for it. | ||
| Jimmci9 (209.240.205.68) Rating: N/A |
i agree with don.... ive seen several of the tank engines.... lots of military-only acessories... both internal and external....it would be a good candidate for a rebuild... but i don't think i'd try just to bolt 1 in.... | ||
| BrianMCI96A3 (65.40.153.32) Rating: N/A |
A turbo'd 8v71 vs a normally aspirated 8V71... the turbo will probably give you a higher horsepower rating, the fuel economy can depend on several factors, one factor...is it a ddec engine, or non-ddec (electronically controlled) a ddec engine is going to be a more efficient engine. I don't know of anyone who hasn't loved switching from a manual to an automatic, and continued to love it, maybe some would rather push that stick around and build leg muscles (grin), but no-one that I know would rather switch from an automatic back to a manual. Allisons are such great trannys, and with the torque converter lockup, in high range they will give you the same mileage over the road as a manual. Plus an Allison under normal circumstances will last at least as long as the engine, and probably a whole lot longer... whereas a manual... depending on the driver... may need to have a couple of clutches changed out in that same time frame. Brian | ||
| FAST FRED (65.154.176.86) Rating: N/A |
"Allisons are such great trannys, and with the torque converter lockup, in high range they will give you the same mileage over the road as a manual" Allisons produce incredable amounts of heat as a by product of their inefficency.Bigger radiators , oil coolers ect are ALWAYS required. ON a GM I know of no one that has switched and not lost huge % of milage , frequently from 9 or 10 mpg down to 6. I know of a few folks who have made the swop and are eternaly sorry they did. FAST FRED | ||
| Jimmci9 (209.240.205.68) Rating: N/A |
au contrair"....the only time an allison makes heat is when it is operating in a "torque convertor unlock gear"... when a ht740 is in 3rd or 4th, the torque convertor is 'locked"... and is in essence bypassed...so makes no heat, other than the gears going round....stall the torque convertor, on the other hand, and it will get hot fast.... by the way, the oil that goes to the oil cooler is the oil that is circulated in the torque convertor...not the oil that lubricates the bearings and keeps the clutches locked.... | ||
| DonTX/KS (66.82.9.33)
Rating: N/A |
Come on now Fred, several times you have been told of the increased mileage with an Allison, and that they don't make heat when locked up. I gained 2 mpg with my GMC 4905 when I switched to a VS/2-8. I drove a friends GMC 4106 from Charleston SC to Topeka KS, at 80 mph speeds, VS2/8 equipped, and had enough fuel left to go half way back to Charleston. DO NOT try that with your old cheapie shifter tranny, you would blow the engine trying for 80, and have to refuel several times. Where on earth do you come up with some of that stuff? | ||
| dougthebonifiedbusnut (24.62.99.43)
Rating: N/A |
Wait a minute Don, I dont know what a vs2/8 is but from what im reading I think you are saying its an automatic. I will tell you there is no way in hell you will ever get the fuel milage out of an auto that you will get out of a properly driven standard.The top speed has little to do with the longevity of the engine. Most caoches geared at 370 or higher cxan cruise all day at 80 and the engine will only be spinning at about 2k or so. | ||
| TWO DOGS (63.185.64.222) Rating: N/A |
Don is a friend...but,,,I agree with the last guy | ||
| DonTX/KS (66.82.9.28)
Rating: N/A |
I rest my case! Your statement that "I will tell you there is no way in hell you will ever get the fuel milage out of an auto that you will get out of a properly driven standard." is simply untrue in most applications. Do you REALLY think that an 8V71 burns the same fuel rate at 2000 rpm as it does at 1700? I can tell you it don't! A VS2/8 IS an Allison, it is the original equipment transmission in many buses, and is a considerable overdrive (as opposed to the V730 which INCREASES the engine speed at the same mph over the stick tranny.) I must add however, this conversation is talking about the V drive buses, I know nothing about an Allison 740. | ||
| TWO DOGS (63.185.64.222) Rating: N/A |
o.k. yep if it's an overdrive..it would get better mileage on the highway...ALSO...everybody...there is a 8v92t with a 10 speed on"that place"...if anybody wants ,I'll post the article number...has 275,000 miles(just now broke in) | ||
| DonTX/KS (66.82.9.52)
Rating: N/A |
Too bad too Two Dogs, they just don't make them for Eagles. I would still love to have a real 10 speed, with some low numbers on the rear axle for some REAL economy AND fun to drive. Drove one in an Eagle with turbo'd 8v71, a real sweetie to drive. | ||
| phil potter (216.234.126.132)
Rating: N/A |
I'm going with a 6v91 with an allison trans. matching set. thanks, phil by the way, the 8v71 military rebuild for $1,600 plus shipping was a "second chance offer" on ebay that was a fraud. It didn't appear to be coming from the owner and it wasn't. Bad boys out there in China somewhere. | ||
| DonTX/KS (66.82.9.83)
Rating: N/A |
I bet you meant to say 6V92, right? | ||
| phil potter (66.103.227.85)
Rating: N/A |
yes. That 6v91 is rare to find! By the way, what do you think of the Allison H748, 4 speed? | ||
| Scott P. (68.121.189.136) Rating: N/A |
I've got a HTB748 in my Bluebird. No problems in 135,000 miles, even with the 8V92 which I have heard is a bit beyond the torque and/or HP specs for this trans. I haven't been able to find any published specs though to confirm the trans ratings. Anyone know? | ||
| phil potter (66.103.227.243)
Rating: N/A |
I saw on one of the threads that someone said it was rated to 360 hp. | ||
| Johnny (4.174.103.101) Rating: N/A |
Just a quick point--US tanks haven't used diesels since the M-60A3. The M1 uses a turbine. | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
Correct. However, Uncle Sam who is VERY rich and weird uses the Detroits in all sorts of neat military stuff like, APC's, dump trucks, tank transporters, skiploaders, fuel trucks, etc.. Sometimes the power ratings were simply incredible. Anyone want a 8V92TI rated at 800 hp at 2500 rpm? And these are not even Marine ratings which are sometimes higher. | ||
| Johnny (4.174.91.73) Rating: N/A |
That sounds like a PERFECT swap for a General tractor! The current flame-throwing 2400RPM 8V71 is just not adequate.  Probably need a bigger radiator, though. |