Hi everyone,my question today would be ,what & how is the tranny made to up shift to a higher gear ,my rig ,,91 breakaway 5.9 4 sp allusion seems suddenly to not shift until 2400 rpm is this normal? Also now I am running along the hwy doing 45mph at 2000 on the tach, using a lot of fuel. Florida Detroit Diesel Allision diagnosed the problem as burnt clutches in the forth gear causing slippage so they installed a rebuilt tranny to the tune of $2236.00 ,but there is no improvement, I sure feel snookered. Any help would be good Paul

If I remember right there is a throttle position rod that tells the transmission how far the throttle is depressed and therefore when to shift.

Thanks for your in put Gary,you pretty much got me into this BARTH THING AS I first was attracted to your coach for sale in the foothills a couple yrs ago it was the brown one ,, no regrets but does anyone know what that 5.9 / 3.73 rear end should shift at.

Paul, can you take it back to Detroit Diesel/Allison? Allison should have the specs as to what speed you should be doing at 2000RPM. If the book says 45 mph, they should give you your money back. Same related to shift points. My '93 shifts somewhere around 1500RPM. Again, will check it out and get back to you. I would call Allison tech line in Indiana @ 317-242-5000. I have talked to them before and found them to be very helpful.
Jim

Paul, I looked up a computer program and assuming you have a 3.73 rear end and 4th gear is 1 to 1, and your tires are 8r19.5, at 2000RPM you should be going 54 MPH. If you are running 225s you should be going 51MPH at 2000RPM. I'm pretty sure that the 4-speed in your Breakaway is 1 to 1 in 4th gear. All of that assumes no slippage. Your transmission does not have a lock up 4th gear, so I would guess that there might be some slippage, but not much if you measure things on a level road with out much load on the engine. Is it possible that your speedometer is out of calibration? If it's a Lucas, there are some steps to calibrate it. Call Lucas. If you have a GPS, you can check your speed pretty well with that as well. BTW, you didn't say what gear you were in when running 45MPH @2000RPM.

Happy ST. PATS Jim,, thanks for all that good help I will be returning to FDDA PRETTY SURE THEY MISDIAGNOSED MY PROBLEM, THEY PROBABLY WANT TO SELL TRANNYS & ARE FAST PART CHANGERS,I will get them to adjust the modulater linkage. My speedo is ok I HAVE CHECKED IT AGAINST THOSE ROADSIDE RADAR SIGNES THAT WANT YOU TO SLOW DOWN.. THAT WAS 4TH GEAR AT 2000 RPM.tHANKS AGAIN FOR YOUR HELP. pAUL

Paul, is it possible that the problem is the governor? The shift valves are in the body of the transmission and since that has been replaced, I wondered about the governor. Hope one of the more knowledgeable folks can help. I still would call Allison in Indiana
Jim

Hi Jim ,the 2400 rpm shift started with the original trans, that's where I got the idea of the trans slipping in 4 th gear but this all started with driving down here thru sand & salt then sitting for almost a month, that also seized up the front brakes so it is looking like the linkage alright , will be calling ALLISION TECH LINE IN Indiana for sure , thanks again, will be back in Ocala wed . morning , will let you know the results of this all, it might help some one else in the future

Dear Jim & Tere have gotten back home found the Allision dealer where a knowledgeable tech looked over my shift problem, still shifting at 2400 rpm in every gear every time , he quickly traced the trouble to a seized modulator cable, a $200 fix . I did not need a new transmission & that's why my rig ran the same after the rebuilt was installed. But I could not get Florida Detroit Diesel Allison to check out this linkage. Gary Carter was right , right from the start, thanks Gary. Everyone steer clear of Florida Detroit Diesel ALLISION IN Ocala they do not know their business.

Wow! I would call Allison corporate headquarters. You need to be able to get your money back. Go all the way to the top.
Jim