deerslayer1979

Ok dad just bought a 96 F700 with a P-pump Cummins 190hp engine and the above Allison AT545. This thing is a pouch, it shifts through the gears really fast and doesn't seem to have any power. The motor runs great, minus it shuts off if you lift off the throttle to fast, but the trans feels like it is slipping. The stall speed at takeoff is at least 1800rpm and if you back out of it at speed the rpms drop down to 1000-1200rpm but as soon as you get back into it they jump up to 2200-2300rpm. I am not an auto guy so I assume the torque converter is toast, but I want to make darn sure of that before I tell dad he has to rebuild it. So can anyone tell me what to look for or what to adjust? One more thing, there is a lever on the same shaft as the throttle that is worn out, it has a cable that connects to the trans. This leads me to believe it is the kickdown, being that the lever is messed up could this cause the sloppy feel that the trans is giving me? Or am I going to be rebuilding this trans?
Thanks,
DS79

wannadiesel

Actually that sounds pretty normal for one of those trucks. They don't want the motor to lug I guess.

Riflemanusmc

Take it into a NON GM Allison dealer and have the tranny flashed/ updated. No, they should not be that way...One of my buds at the DD dealer I worked at can work magic with a laptop.. Its all in the tech doing the work...

deerslayer1979

If this thing had a computer I woul take it to work and hook it up, but this one is all mechanical. It has to be something in the linkages. I looked at work, but we dont have much on these old Allisons, we deal with most of the new stuff. I am going to call the local Ford dealer and get some parts that I need and hopefully they will have the adjustments I need to get this thing to work properly. BTW wasn't there someone on here that had one of these in his 1st gen that he used to pull?
DS79

74dart

We have a HT-740 in our old mack and it dosent run like that. Ours will hold the gear untill enough RPMs to up shift. Unloaded at 45 it will not shift to 4 th gear untill it gets to over 50. It feels weird not to upshift but I have been told that is normal.

John Faughn

I've got a 74 Carpenter bus , with a non turbo Cat 3208 , I think it has that model Alison in it .
At 55 mph its RPMs are about 2,500 , seems high , but it does shift into all 5 speeds/gears .
Used to be a fire crew bus for Cal. forestry .
Posting to see what comes ?

74dart

What rear end are you running. When we got the mack it had a double reduction 6.36 with a top speed of 45 at 2100 RPM. We swaped it out with a Rockwell 4.10 now the top speed is 72 at 2100 RPM.

John Faughn

Its been a while since I checked out that info , bought in 91 , only moved between storage area's for the last 17 yrs.
I think I remember it was a Rockwell , but I seem to remember , most of the id tags were missing [ inside the front door ] .

deerslayer1979

Well heres a liitle update on this trans. We finally got it setup to pull the gooseneck this spring, and made our maiden voyage saturday night. It pulls about as well as I had hoped. Got us there and back but by now means were we setting any speed records! I am guessing we wieghed about 25-26K and this thing would barely keep us at 55mph on flat land. Any hill you were down to 35 or less. Motor only revs out to 2250 so that is where I am going to start, but this trans still has issues with shifting, and holding speed. So if anyone has some suggestions on what I can do to help it along, I am all ears.
DS79

DiezelSmoke

190 hp for 25-26k it would be hard to make anymore speed. Good indicator for the shape of this trans is to smell the oil for burning smell. Change fluid and filter.

mini14

sounds like sop for an at545 when i changed from dexiii to overpriced transynd it firmed up the up and down shifts considerably. id take the 545 over the electromechanical ones of today, just wish it had 5 speeds instead of 4