Hi to all We just returned from a 2500 mile trip in the Barth. It seems that I have a 4.11 ratio axle as I top out at 65mph at 2700rpm. Could I get some opinions , could I put in a 6 speed with this axle or would a 5 be better, I've seen some allison 2000MH trans listed. What is the deference between a 2000 and a 2000MH? I know you guys are a great deal more knowledgable . also I"m running 8R 19.5's
Thanks
ps it was a great trip to Ft Leonard wood and back
Wayne

IMHO here is one approach: Contact Cummins with your engine serial number and get the HP - Torque curve sheet.I looked up the generic 5.9 on their site and it appears that 2700 rpm is the goverened limit and that HP varied from 140 to 215 depending on the year. You can look at the curves and pick the sweet spot where torque and hp are the closest and then determine what tranny final drive and/or rear end ratio will let you maximize effeciency and fuel mileage. It is possible to have the Allison final gear changed or, of course, to change the differential ring and pinion. Don't do this only by changing anything until you determine the most efficient point on the curves. Your experience says the engine is operating at its limit and that can't be good. The same
site says this engine was developed for agricultural use and was then adapted to road use. So it is a mis-match, sort of like our old F-4 Phantom - not quite a fighter and not quite an attack bird. A compromise that didn't do either job well.
Good luck and let us know how it progresses.

Hi Wayne, I do not believe that you have 4.11 diff. If you have the Dana 80 diff it will be 3.73:1. Unfortunately there is no compromise with the diff ratio and the trans, further the Dana 80 diff case in your coach will not accept a higher numeric ratio, you are stuck with 3.73:1. Your trans in 4th is 1:1, no over drive and no lock up torque converter. yes the RPM will be near or at the governed limit at 65 MPH.

5.9L Cummins in '93,'94 were rated 190 or 230 HP depending on the application, yours is probably rated 190 HP. Most 30' Breakaway 1991-1993 with the 4 speeds have the 190 HP and 3.73 Dana 80 rear diff. There is a tag on the diff that will tell you exactly what the ratio is.

You would not want the 6 speed with the 3.73 diff as it would not be ideal for RPM/MPH. The 6 speed has a final drive ratio of 0.65:1, very deep overdrive and would only be used correctly with a 4.1:1

My Cummins 5.9L (1993) is rated at 230 HP with the 6 speed and has a 4.1 rear diff. It is a good combination for 19.5 tires but NOT good for 22.5 tires. In those Breakaway applications with 22.5 tires you don't even go into 6th until 70+ MPH.

There have been recent discussion about this issue. You could go with the Allison 2000 (as Gary Carter did )which is normally a 5 speed and that would work better for cruise but still would be slow off the line as it is now. 1st gear ratio is nearly identical with the Allison 542

quote:

5.9L Cummins in '93,'94 were rated 190 or 230 HP depending on the application, yours is probably rated 190 HP. Most 30' Breakaway 1991-1993 with the 4 speeds have the 190 HP and 3.73 Dana 80 rear diff. There is a tag on the diff that will tell you exactly what the ratio is. You would not want the 6 speed with the 3.73 diff as it would not be ideal for RPM/MPH. The 6 speed has a final drive ratio of 0.65:1, very deep overdrive and would only be used correctly with a 4.1:1

Right after Vince (PO) bought the coach, he invited me to see it. IIRC, it has a Banks kit, and the engine is rated at 215 HP (stock 190). That means the Cummins torque/HP curves won't apply.

I agree that it probably doesn't have a 4.11 (but likely has the Dana 80). Comparing the RPM/speed, it might be a 3.9x. I suspect, however, it's a 3.73.

I recall on some previous posts that the most efficient operating range for the 5.9 was between 1700 and 2400 RPM. So I guess with a 373, 2400 RPM would be around 60MPH. So, if you want to be able to cruise faster, the 6-speed would be the only way to go. But considering the cost,(as I recall,around $5000 if you have it done) I would probably wait until I could buy one that already had it installed and then sell the one you have. You might also have the option of going to a Barth with a Cummins 8.3 and 6-speed.
Jim

Wayne has the same limitations I had (now turtle has) w 5.9 and four speed. I think it was intended to cruise @ 60mph, or maybe even 55. Fortunately, it didn't make any difference if I was towing or not, unless I had to climb. It simply isn't cost effective to make the radical retrofit of a newer, more efficient tranny. As Jim says, the solution is to change coaches entirely. must have been the following year when the 6 became prevalent.

Thanks for the replies. Does anyone have the codes on the tags my ratio tag reads "080AF1071 07790D the tag above it reads TFI236RR3-2. On the Spatran Placard it says DANA 80. On other Rarth placards it says Dana 80 3.73. Mine has the number whited out. Also I did run down I-95 on a long flat stretch wide open and saw 2700/65 mph, the the fastest speed on the trip was going down a hill in Mo at 68mph.
Rusty I did look and It does have a Banks kit, Vince said he was told it had 210hp.

I suppose it is possible that someone replaced the diff but until you get numbers off the tags on the diff it would be hard to speculate what you have. The tags should be there unless someone pulled the diff cover and didn't put the tag back on

The Dana 80 was built using two sizes of diff cases, for most of the Barths using the Dana 80, it was the smaller case and 3.73 was the highest numeric ratio ring and pinion that could be used. But we also have so many times on this forum "all Barths are different".

Using tire spec ratings for 19.5 tires 628 revolutions per mile should equate using 3.73:1 diff ratio:

60 MPH = 2342 RPM
65 MPH = 2537 RPM
70 MPH = 2732 RPM

This is just a raw calculation. Other factors such as accuracy of the speedometer and tachometer will influence what you see. By chance did you use a GPS for speed verification? My speedometer was off by 3 MPH when I first got the Breakaway. I recalibrated the speedometer and then later when I changed to 225R70 19.5 had to recalibrate it again. I know my tach is off but no way to recalibrate.

Lastly, tire pressure and tire wear, will change the rolling radius and give incorrect speedometer readings. Your 542 transmission does not have a lock up torque converter so there is slippage there, it can be a hundred RPM or more higher than the calculated RPM should be.

There are some '91 Breakaways with the 5.9L engine and 6 speed but these are all 32' or longer. I have not seen another 30' Breakaway like mine with the 5.9L/6 speed.

Let us know what you find from the tag on the diff.

I checked the gps against the mile posts and at 60 mph it took 60 sec for a mile, at just over 2500 RPM. I have 8R 19.5 toyos that have 2000 miles, they are inflated to 90 psi which is per the chart and actual weight. Does anyone know a link to the dana tags?

quote:

Originally posted by w&bknocke: Does anyone know a link to the dana tags?

UMMM, the previous post I sent should show where to look for the ratio tag. The Numbers you sent are only generic for the diff case size etc. Look at the bac k of the diff, the tag should be there.

And note:

1. On a pusher, the back is to the front of the coach, AND

2. The diffy will be flipped over, so the top is the bottom...

You have the 3.73 rear end. I have done lots of posts related to changing to a 5 speed Allison 2000 5 speed. With the Allison 542 top end was 65. Keep in mind this chassis was released when the speed limit was 55.

Ok you were right. Just talked to Dana and they said 080FF107= 3.73 Now I need to figure out why I'm turning 2550 @ 60mph .


Thanks for the help!

2550 might not be that far off considering accuracy of the Tach, the speedometer, and any slippage in the torque converter. According Toyo's website the 8R19.5 tire turns at a rate of 616 revolutions per mile. The pure mathematical calculation would be 2298 RPM at 60 miles per hour.

616 times axle ratio of 3.73 equals 2297.68 and 60MPH equals 1 mile per minute.

Nick

Yup that means I'm loosing 10% to the torque converter.I guess I'll follow Gary and go for a 2000 5 speed as $$$ allow. BTW I've looked at SOB's and putting another 5-10 into my Barth is still a bargain
Wayne