| Author | Message | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Well, now that I have my nifty eaton 9 speed w/ overdrive all working perfectly, and now that we've been on three trips totalling about 5k miles, yup, you know what the wife said... "watching YOU learn to drive that 9 speed, ther'es NO WAY you'll get me in the drivers' seat"... ...Soooo now that I've been thru all that to get the eaton in, I'm thinking seriously about dumping it, starting all over and making the bus automatic. I have a buddie who will virtually give me an Allison 643 that is in excellent condition, and I already have a 4:11 rear end that if I install will be the same final ratio as I am at right now with the 9spd (and am happy with)...the question is, is this a viable tranny for my Crown? The bus currently weighs 29,000, and I doubt my engine will ever put out more than 230hp, so looking at the specs it looks good- but I don't know trannys so I thought I'd ask ya'all.. Cheers Gary Stadler who just loves to beat his head on the wall | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
Gary - FYI - Crown put mostly HT740s in the midship models, but they did use the MT series in some of the pushers. The MTs are mostly for the bobtail trucks - like the ones you see delivering for Sears or Circuit City, etc. A Medium duty tranny. Maybe not the best for severe stop 'n go use, but probably OK for RV applications. HTH, RJ PD4106-2784 Fresno CA | ||
| Johnny (63.159.197.132)
Rating: N/A |
"watching YOU learn to drive that 9 speed, ther'es NO WAY you'll get me in the drivers' seat"... And this is a bad thing how?  Sorry--couldn't resist. My wife won't drive my skoolie--or any RV. Maybe try to persuade her that yes, Virginia, she CAN learn to drive a crash box? | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
I have to admit that learning this one was more of a pain than I anticipated. For one the speedo currently says 112mph when I'm doing 60 'cause I havnt had it calibrated yet with the 9 spd, and for two, it's almost impossible to see the tach from where you sit. (Bad Crown...BAD!!) so right now shifting is mostly by "feel" or by "ear". The bug is when I have to switch between hi and lo range...if I miss it, I almost have to just stop the bus and start again from scratch, because it's virtually impossible to tell where I need to be. Added to the fact that the first two trips invloved 5 hours each of fire-roads in the mountains and that the shifter itself moves only about 4 inches in any direction (it's a REAL tight pattern!...) it probably looked near impossible to my wife. I felt like it was a few times myself!! I'm sure that when I get my new cluster installed next week (a much larger gauge panel I nabbed from a '79 Crown that has the tach and speedo where ya can actually see them) and get the new electronic speedo installed it will be a lot easier to shift. But I still want to consider the auto and what the pros and cons might be. Any more thoughts would be appreciated... Cheers Gary | ||
| neil (198.81.17.22)
Rating: N/A |
I spent about $10k putting a 647 in my MC5 so my wife could help with the driving. Guess what she drove it twice for about a total of 3 hours and said "you drive and I'll cook". Not a bad deal since I kind of like driving anyway. I must admit that I really like the 647 it makes driving a pleasure. Just don't do it planning on getting any help from the wife. I;m curious where you were on the fire roads? That sounds like the kind of stuff we like to do. Neil | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Niel, A few questions- First and foremost I'm wondering how your tranny works on grades- having a 9 speed means I can pretty much select the perfect gear for maximum speed and RPM when Im going up a long grade. But how does the 4 speed auto do this? I've been told that the torque converter takes care of it- is this true and do you experience any less performance than with a stick? Also how's about gas mileage...did the auto decrease it by any noticable amount? Currently I'm getting about 10mpg and I'd love to leave it that way... Last, of your $10k that you spent, how did it break down aproximately, ie how much for the tranny, how much for extra parts, and how much for the labor, or did you do it yourself? I just blew off about $4 grand getting the 9 speed going and I don't want to spend a lot more...I'll be getting the allison tranny basically for free and doing the work myself, so I'm wondering how much more it will set me back... The bottom line is that I really like my 9 speed but I just can't drive all the time, especially on some of our longer planned trips like cross country... and it frustrates me to my end hearing a giant rattle that my wife can't or (won't) find, and not being able to chase it down while I have to drive... granted those will go away one by one over time, but it's very handy to be able to leave the wheel in various circumstances and frustrating not to... We drove around in the Santa Cruz moutains last trip to end up with with a bunch of friends at a remote campsite... did the same thing about 50 miles outside of Vegas last week, and have friends ALL over the country that we want to visit. I picked the Crown purposely for it's high ground clearance, and I got a 35 footer instead of a 40 for the same reason. I had a 40' pusher a while back and though I love the space, it was hard to navigate some of those dirt roads... Cheers! Gary Stadler | ||
| Rodger Manecke (216.170.151.84) Rating: N/A |
Gary, Our 35' Prevost Champion, with an 8V71 NA, has an MT644 installed. The retrofit was done for the original owner/converter by a bus shop in Durham, NC. I'm having a senior moment and don't remember the name, though it's occasionally mentioned on this board. Maybe Gary's Coach?? At any rate, the MT644 is probably similar to a 643. It's a 4 speed. The torque converter locks in 2nd gear. My guess is at least 125K miles have been put on it since the retrofit. I have no idea what are the total miles on the tranny or whether it has ever been rebuilt. It appears to be still healthy and performs fine. In extreme conditions the temp gauge has reached 195 deg, but in normal conditions it stays around 140 to 170. The fluid has about 29000 miles on it. It's still clean and red with no signs of overheating but will get replaced soon. Upon buying the coach, I had the fluid replaced and the old fluid analyzed. The analysis reported the fluid was very dirty and slightly burned. No significant amount of metal was found. An external filter installed at that time. Most of the time, I manually select the gear I want, because if left to the tranny, it frequently shifts too soon on the upshifts and too late on the downshifts. Down shifts are a little rough and the up shift from 1st to 2nd is hard unless the throttle is floored or nearly so. A couple of Detroit/Allison shop mgrs have told me this is normal for an old Allison. For descending long grades, I think the torque converter lockup in 2nd gear is important. I don't have Jakes. In the mountains, for descending 6% grades to 6% and keeping the revs at 1800, 3rd gear is generally adequate to avoid excessive braking. For steeper grades I use 2nd gear. Going up, I use about the same gears and keep the revs at 2000. The coach weighs around 30K LB loaded for a trip and we pull a 3100 LB Honda. Average fuel consumption over 28,000 miles coast to coast and boarder to boarder is just under 8 mpg. The tach reads 1800 rpm at 60 mph in 4th gear. I've been told a few times that MT640 series Allisons were used extensively in the older Bluebirds. From my experience, it appears that an MT640 series is very adequate for a 30,000 LB coach with an 8V71 or engine with similar torque/HP. Hope that helps. Rodger | ||
| Neil (198.81.21.178)
Rating: N/A |
Gary The Automatic has worked well for me. On those long grades we just slow down. You have to down shift,the tranny is not set up to down shift soon enough for my 8v71, I don't know what kind of and engine your running. If it's a cummings your tourque is curve is lower than mine, so you might not have to downshift as soon. All in all I really like the change. But then again we had a 4 speed crash box before and any change would have been an improvement. As for fuel. We get about 7, I think we lost about 1/2 mpg. Cost-- I don't know because Gary at coach services put mine in for a set fee. I think with a free tranny it wouldn't be much. We like to get back in the boonies to. We are in Albuquerque NM now, after living 40 years in So CAl.If your ever up this way stop in we are building a house on 2.5 acres and have lots of room. Last summer we were in the Northwest all summer and most of the time we boondocked in the Nat. forest. Did you know you can camp anywhere in the Nat. forest that is not posted "no Camping"? You can stay in one spot for 14 days and then you have to move. We are usually ready to move anyway, as thats all the water we have. God bless Neil | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
Gary, the 643 Allision is nearly a perfect match for your application. A 740 series tranny would be overkill. With a 4.11 case, you should have around 60/65 mph at 2100 and with your pump set at 2500, around 70/75+ mph give or take. Even with a mild turbo, your 743 will be putting out "only" 230/240 hp with 600/650 torgue which is fine for the 643. This box is also much lighter and somewhat shorter than the big heavy Allisions. Crown hung lots of 643 trannys with the 671 Detroit, even some with mild turbo specs. Bet if you check the wrecking yards, (and the special one down south) you might find the stuff necessary for a change over. Again, with your weight and power, the 643 would be just fine. The problem would be finding out if the fan setup on your radiator would be good enough to cool that tranny oil with the oil cooler hung outboard of the radiator. Or.... you can just go to work and learn how to shift that 9 speed. You have 42%, 40%, 38% and 37% or sooss splits with the Fuller. Upshifting is going to take a little time to complete. I bet with practice you will do just fine. Then you can teach your wife how to do it sooos you can nap in the back while she drives. Sounds ok to me. All it takes is determination and practice. Heck... look at me. Even I can shift a RTO-910!! (Actually my fire captain Brother taught me how!) You really amaze me. Wish I had one tenth of your energy regarding Crown conversions. My excuse right now is awaiting some property to sell soossss I can do MY Crown RV thing. Good luck and ...... CROWNS FOREVER!!!! | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Tail between legs... thanks for all of your input but.... After probably 5 hours of talking to people on the phone today including Allison, I guess the 643 just wont go in. It is a perfect match as far as HP and torque, and this tranny was just rebuilt a year and a half ago so it's top notch shape. But the bummer is that evidently Cummins quit making the 743 just a few years before Allison started making the 643 and there's absoutely NO parts ever 'been made to mate the two- namely the flywheel stuff and flex plate. I've talked to three big tranny shop foreman now including the folks who rebuilt this one, and every one says "nope, get a 647- that one will be easy but the 643 won't go". Evidently it's how far the torque converter sticks out into the bellhousing, and the fact that no flywheel/flex plates were ever made for this combo. The drag is that they won't even give me enough of a core trade in value for this one to make it worth it, and so darn, I've gotta say uncle this time. Poohy! So if there's anyone out there who wants a really nice fresh 643 for a grand, I know where it is and I'll tell ya! ...now how do I convince the wife that the 9 speed isn't impossible...??? Cheers Gary | ||
| Jojo Colina (Du1jec) (209.75.20.72)
Rating: N/A |
I have an MT-650 which was overhauled and never installed. See if you can use that. I'll let it go for $1200 and it is in San Diego. | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Jojo- I called my tranny people and it turns ou that the 650 is physically identical to the 643 but it has 5 speeds instead of four. So it won't fit either...evidently all the shops say 'tis only a 647 that will work. Sorry, or I'd have said yes! Cheers Gary | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
Gary, what I think you need is the older Allision HT-70? I think this was an older 6-speed auto that Allision had way back in the late '60's. If memory serves correctly (incorrectly?) Crown Coach had a demo schoolie with this tranny (with a 743) which they showed off to the Kern High School District in sunny Bakersfield CA in 1969 or soosss..... Where I was driving part time pretending to go to junior college. Everyone loved it except the boses who wanted to stay with the tried and true RTO-910 Roadranger which was/is sooos cool. I THINK this tranny had a double overdrive with around a .56 to one high gear??? (same as the current 'new world' models?) Maybe not. Also an optional deeper ratio model? Anyway, thought I would let you know for whatever it is worth. With this auto, you may not have to change out your current 5.12 rear case. This tranny was neat in that usually you started in 3rd gear and it shifted as a 4 speed. You also had the option of starting in either 1st or 2nd also. The shift pattern was (I think) 1-2, then 3-4, then 3-5, then 3-6 along with the "N" and "R" positions. First and second were kinda low. Crazy how long term memory works or does not work. Yea, it is coming back to me even as I try to think. The gear sets were a even 33% step between gears, with the optional "deep ratio" of around 36% or soosss to one. Fourth was direct, fifth was 33% over and sixth was another 33% over I think? I may be wrong with the double overdrive stuff, but I believe the 33% gear drops between gears is accurate. And yea, the tranny had a lock up clutch. Anyway, I am telling you this because maybe you can find a good condition HT 70 to trade for your current 4 speed which will not fit your 743 soon to be turboed Cummins. Good luck and CROWNS FOREVER!!! | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Well might be a great tranny for me, but for now I think I'll just wait for a while. I was hot on the 643 idea because it was such a good condition tranny for almost free. But I just got broke again... yesterday I scored a virtually new Onan Marquis 7kw genset on ebay for a relative song (a 2000 model that was in a wrecked motorhome with less than 2000 miles on it, and poorly listed so no-one serious bid on it but me!) and today I scored the turbo exhaust manifold I've been searching for, from a junkyard up in Portland, so I ordered a new garrett adjustable exhaust-gated turbo for my altitude compensator. So I won't be buying any tranny now for a long time 'till I work the new bills back down, but very soon I'll be dirving in horsepower heaven up at high altitudes, and enjoying QUIET electrical power when I land instead of having to listen to that that nasty generac I now have!!! Cheers Gary | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.164.175.3)
Rating: N/A |
When does the Jake get installed? Brrrrooooommmmmmmm! He he he. CROWNS FOREVER! | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
I've got an exhaust brake on my rig that works just fine. It certainly won't toss you thru the windshield when you put it on, but it allows me to come down 6-1/2 percent grades in 8th (1:0) with maybe one stab-brake in 2-3 miles. Perfect!! Now the question is, this brake only gets the exhaust pressure up to 30 psi at most. THe gauge on it goes to 60... How high can I set it and not screw things up? Cheers Gary | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
As high as you can before the manifold pressure begins to push the exhaust valves open then they hit the pistons and bad things happen. | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
...sooooo's there any specs, or do I just have to take a wild guess and hope? I seriously doubt if even 60 psi would hold the exhaust valves opened though, because the springs are monsterous, and I'd think that excess pressure in the exhaust manifold would tend to leave an equal excess pressure in the cylinders when the valves closed, making everything equal. Even if it did have enough oomph to crack a valve opened, it would then leak down so fast that they would only be held opened a few thousandths of an inch. My guess is that it would be other problems that would crop up, ie since when the exhaust valve closes, the cylinder is now left with 30psi in it. When the intake valve opens there will now be a blast of air going the wrong way out the intake manifold. Cummins actually specifies a pulse muffler be put inbetween the intake manifold and the air cleaner on engines equipped with exhaust brakes, because evidently this blast can and does wipe out paper air filter elements. Maybe 60 psi would do worse things..?? but since I'm no expert on exhaust brakes, that's why I asked! I'm still wondering.... | ||
| RCBishop (128.123.62.233)
Rating: N/A |
Si, Henry....."it's a rear view mirror thing". Least that's the way I "view " it..hee hee hee. Try it, you'll like it!. RCB | ||
| R.C.Bishop (128.123.62.233)
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Don't have the slightest idea how the above got into this thread....it belongs in the thread above.. So solly. RCB | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
That is because they let ANYONE on this great board including ME!!! The crack about the valves hitting the pistons was meant as a little joke. I have NO IDEA if that would actually happen. Suspect instead the gaskets would start to seep/weep/blow or like already said, the pulse would back up thru the mill and wipe out the air cleaners. However, somewhere in storage I have a nifty little booklet that lists all of the various maximum pressures allowable with different mills using exhaust brakes. Now.....if I can just figure out where I have put it, I will find out if it lists the older 743 Cummins and if it does, I will get the figure and get back to you. Great board and I am sorry. |