Please Let me know what your RPM's are at 60 mph.The Allison rep at the Super Show Tampa, said he could get rid of the slipping in my 542. I'd like to know what RPM other breakaways operate at 60 MPH.
Thanks
Wayne

I am thinking you want to narrow this down to those with 4 speed trannys? I have a Breakaway but my Allison is a 5 speed and there may be some with a 6.

Tom Taylor
94 Breakaway XL

Ok 4 sp allison 542 with 19.5 wheels

Like to know how he plans on getting rid of the slip. There is no lockup convertor.

OK with no slippage your RPM will be 2286. That's what the math says. Tire is 613 rev per mile and RE ration is 3.73.

The Allison rep says the new 542 converters do lock
I don't know if he is correct or not.

I have 6 speed in my 30' Breakaway and it does lock.

It is not possible to put in a lock type torque converter in the 542. It is possible to put in a low slip converter but still it will NOT be a lock type.

This is well discussed on the internet particularly when people want to install a Pacbrake or some type of engine brake. With out a lock type converter an engine brake is just a waste of money and does not work well, with a low slip converter an engine brakes will have a little effect but still not at all acceptable.

There was a 1542 that featured a lockup convertor. I searched nationwide for one before buying the 2000. I do have a spec sheet on it, but that is all. I was told it was used by the military.

What does the rep mean by a NEW 542. Last production date was before 2000 I believe.

That is my problem. I think he is trying to sell a reman because it is easy money. He said all the Fed x trucks use 542s. Gary Is yours a 2500 ? if not which model did you use.
Thanks

quote:

Originally posted by w&bknocke:
Please Let me know what your RPM's are at 60 mph.The Allison rep at the Super Show Tampa, said he could get rid of the slipping in my 542. I'd like to know what RPM other breakaways operate at 60 MPH.
Thanks
Wayne

Around 2300 or so as seen by my jiggling eyeballs.
What of mileage are you getting Wayne?

Nice math!!

quote:

Originally posted by Gary Carter:
Like to know how he plans on getting rid of the slip. There is no lockup convertor.

OK with no slippage your RPM will be 2286. That's what the math says. Tire is 613 rev per mile and RE ration is 3.73.

about 9.5-10 mpg

Some might like this.


Tire RPMile
Tubeless Tube Type

8R19.5 = 613
9R22.5 = 542 = 8.25x20
10R22.5 = 520 = 9.00x20
11R22.5 = 504 = 10.00x20
12R22.5 = 492 = 11.00x20
11R24.5 = 480 = 10.00x22
12R24.5 = 470 = 11.00x22


Engine RPM x 60
MPH = --------------------------
Final ratio x Tire RPMile


So now you just need to remember High School Algebra to get whatever piece of the formula you need.


Sorry for the bad formatting. It was correct as I created it, but reformats itself when posted. It deletes all leading spaces and I don't know how to make it right

quote:

Originally posted by Gary Carter:
Some might like this.




8R19.5 = 613 RPMile

FWIW, that is the exact number Bridgestone publishes for my tires.

But of course the plot thickens:

Yes with standard 8R19.5 the RPM would be as stated. BUT if one were to change to 225/R70 19.5 the engine RPM would increase to 2409, an increase of 123 RPM at 60. Again this would e with no converter slippage.

Mine isn't too bad, because at 60 my engine RPM with 8r19.5 is about 1633, with the 225/R70 19.5 my engine RPM at 60 is 1721 an increase of 88 RPM. Not too much but is noticeable. I am kinda used to it now.

Would have loved to put 245/R70 19.5 as they have the same rolling radius as the 8R19.5. 245 demand a wheel width of 6.75" or more and the 245s would touch on the equipped Alcoa 6" width wheels.