| Author |
Message |
Duane Kaler (Duane)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 02, 2006 - 10:07 pm: | |
I have a chance to aquire this transmission but I dont know if this is a good match in a bus with an 8v92. I need to know if it is an OD trans and if it is rated for that kind of power |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 02, 2006 - 10:30 pm: | |
I have already been thru this drill. The 754 is a 5-speed transmission. It does not have an overdrive in it. The final ratio is 1:1 just like the 740 4 speed. There are two kinds of 754 one that has a lower 1st gear than a 740. The other has a 4th gear that is a ratio between the 740 3rd and 4th gear. It will take the torque of an 8v-92 without any problems. I have not found anyone that can give me a definite answer as to if it helps anything. When I was over at the Allison distributor to get some parts I talked to an old mechanic that was rebuilding one out in the shop. He said it was not worth the money to change over from a 740 4 speed.
If your old transmission were shot than I would say it couldn’t hurt to replace it with the 754.
Otherwise it does not seem to be worth the expense to replace it.
If you want overdrive you need a B500, 4000, or a 4060 transmission. These have a great benefit when you have a 4 stoke engine and want to drop the rpm down. The 2 stoke usually does not like to pull at 1500rpm so it may not be a big advantage for the 8v-92.
I am going to boost my 8v-92 up so I will have shaft-breaking torque and will not need any more gears. (Go for the 560hp rating with M15 injectors)
Good luck with your project. |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 02, 2006 - 10:55 pm: | |
One other thing I forgot. If you do put the 754 trans. in your bus be sure you get the correct torque converter ratio for the 8v-92 engine. There are many diffent numbers for that and you would need Geoff or somebody to tell you which one you need. The shift points need to be set correctly for the 8v-92 in order to get the best performance out of the 8v-92.
Good luck finding that info. |
Duane Kaler (Duane)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 12:16 am: | |
Thanks for the info Greg. As I am replacing a manual trans maybe I will just find a 740 to install.
Thanks again for the info. |
Ron Walker (Prevost82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 11:51 am: | |
Well I don't know. I run my silver 8v92 at 1500 rpm all day and it loves it. I talk to several old DD mech'ic and they said that 1300 rpm on the flat is find with a silver..and as long as your not lugging it. Alot of trucker that run silver 8v92 in the 80's said the same and there are a lot of truckers that ran DD in the 80's here and most were hotrodded to over 500 hp
Ron
They're a bunch of B500's for sale at truck parts |
Duane Kaler (Duane)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 12:59 pm: | |
Will the B500 work with the older non electronic engines? |
Ron Walker (Prevost82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 3:56 pm: | |
Duane ...I talk to allison and they said "yes" it will work. You need a throttle position sensor and an electronic speed pickup....which most busses have for the speedo.
If you don't want to regear, you can program the B500 to be a 5 speed trans /w 1 OD 5th gear (.74 : 1) 60 MPH @ 1300 RPM (standard 3.73:1 diff)
Or you can put in 4.67 : 1 gears in your diff to use all 6 gears... in 6th gear /w this ratio you would be running 60 MPH @ 1402 RPM |
Duane Kaler (Duane)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 5:47 pm: | |
OK, heres the deal. I currently have an MC7 with an 871 with a 4 sp manual. I dont have a tachometer in the bus. I drove the bus home about 1200 miles. I got around 9 miles a gallon. I ran about 60-65 mph. As I am not used to the 2 strokes she realy sounded like she was screaming along. I had to put new tires on before the trip home and I chose to go with 1200-22.5. The diff ratio is 3.70. Now I dont know what is a good rpm for these engines to run at all day long. I would like to be able to cruise at 70 on the flats. I do plan to build a heavy coach and pull a load in the 6000-7000 pound range. My plan is to go with an auto trans in the beginning but I want to go to a bigger engine down the road. I am thinking 8v92 0r the 12.7 four stroke. So the question is can I install an auto trans that woud work for now and any changes down the road. I would also like the pros and cons on a 10spd roadranger.
Thanks for any advise, Duane
(Message edited by Duane on June 03, 2006) |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 03, 2006 - 10:06 pm: | |
Before I got my bus I had an RV with a mechanical 190hp 5.9l Cummins and an AT540 tranny. This was a terrible setup for various reasons. I ran into a “deal” on a new style computer controlled 300hp 5.9l engine. I decided that I would replace the old engine and tranny with the new engine and a rebuilt overdrive tranny. The guy that was selling the engines gave me the names of some other guys that were doing the same thing.
We all managed to convince each other that it would be easy.
Even though they were both 5.9l Cummins the fan and other things were just enough different to make the motor and tranny mechanical install a real adventure. The next thing was all the wiring to the computers and the electronic gas pedal. This was a complex mess that required hard to find connectors for the engine and transmission computers. Cummins and Allison only have the parts that are on there modules. It is up to the OEM to supply the other side. If you go to freightliner they want to sell you a $1500 wiring harness that is not correct anyway. I had to run down the mating connectors from several suppliers with minimum orders and all kind of other expensive conditions.
After another 10 chapters I could write about the install I was done and went to test-drive the vehicle. I had a 4.10 rear end ratio that was in with the old setup. I now had a .71 overdrive ratio and I thought I would get super fuel mileage with real slow rpm when I hit that 60mph speed. When it hit 60 it shifted and the rpm went down but I could not accelerate anymore. If you read that Cat RV performance paper in my other post you will see that at the high speed the horsepower required goes way up. Since horsepower is a function of torque X RPM my engine was not producing enough HP to move the RV at the low rpm. I got the torque and RPM curves from Cummins and found out that I really needed to be above 2100 rpm to get the HP I needed.
I changed the rear end gear ratio to 4.63 and everything was real good. It would do over 85 mph at 2700 rpm. I went on a camping trip and was pulling away from a toll both and there was a gas RV on the other side. I floored it since I now had my new powerful diesel the gas guy was not going to beat me. He could not keep up with me but I heard a weird sound like metal breaking in the back of the RV. The rear end started to make more and more noise all the way home. Just before I got home the ring gear exploded in the back end and I had to be towed. After much investigation I found out I had too much torque for the old rear end. This was not easy to find out because it was out of production and nobody cares about it then…kind of like 2 stroke engines. Anyway, I put in a new surplus axel that has 2000 ft-lb more than I need and now it works great.
What I thought to be a fairly easy upgrade took over a year. All during this time I could not go camping and the members of the family had the opinion of “why did you fool with it”. I did beat it in the end but I will never do this again.
You can gear your engine to run at 1200 1500 or whatever rpm but you need to be able to generate the needed horsepower without lugging the engine. Maybe the 8v-92 can do this at 1300 rpm. I have not been able to find any curves of rpm vs. torque and horsepower-- unlike the new Cummins and S60 engines that have curves all over their web site. This is another example of poor support for obsolete products.
I like to have my 8v-92 pull at higher rpm so the fans and water pump run faster in order to cool the engine better. You also are sure you will have all the rated horsepower. It takes torque to get the bus moving but it can’t go fast without horsepower.
It was a big job going from the 5.9 mechanical to the electronic 5.9l. I would imagine the 8v-71 to 4 stroke swap would be even more work. Maybe some of the guys that have done it will give you some info.
Hope this long post gives you some useful info. You should do as much research as possible on this project before you buy anything.
Good luck and post how the swap went and any learning you had from the adventure.
P.S. Some of the other guys that bought the 5.9l engines have not finished their engine swap. |
Henry Bergman
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 19, 2006 - 6:42 pm: | |
Duane: The Allision 5-speed is a direct high gear tranny. It is about 6 inches longer than the 4-speed HT 740. I do NOT know if the 754 would fit in a MCI-7. May not have room.
My Crown has an older RTO-910 10-speed Roadranger and this tranny is very wide, quite flat, and very long. Again, I do NOT know if it would fit in a MCI-7. My Crown is mid-engined. Good luck. |