New to me ford L8000. 3208 cat with mt653 allison. Problem I’m having is it will only shift at wot around 2600rpm. Won’t shift at lower rpms or less throttle. I have pulled governor and everything is working on it. Modulator has been adjusted per manual. Governor screen has been cleaned. If i disconnect the modulator it will shift alot sooner. Like 1500-2000 rpms. Lock up works. Any ideas. Thanx
Hard to say from here but it sounds like there is something wrong with the modulator adjustment. If you disconnect the modulator does it go to the full closed throttle position so the transmission thinks you are at closed throttle all the time? If so what is different when it is hooked up and at closed throttle vs not hooked up? Something does not make sense here.
Click on the "abnormal shifts" in blue at this link http://allisonparts.net/Allison-Transmission-Parts-Tips.html
When you disconnect it. It pulls back in all the way. Has good spring tension. I have not pulled modulator from trans yet. When it’s connected it will not upshift until you reach almost max rpm. About 2600. When disconnected it will shift at a much lower rpm. Around 15-2000 rpms.
You can try letting off the throttle to make it shift and then getting back on after.
I’ve tried with no changes
How is the modulator position when off the throttle different than the modulator position when disconnected?
It’s a pull type cable. Nothing changes when disconnecting modulator cable. It stays put. Fully retracted. When you go wide open throttle the mod cable has just a little slack left in it
If i remember correctly are there not 2 types of modulator cables—push or pull? Also is the cable hooked to the correct part of the throttle linkage. ie. maybe its a pull cable hooked to the push side of the linkage or vice versa. Just trying to eliminate the simple stuff
It’s connected to the correct throttle linkage part I believe. The modulator has spring tension which pulls it back in to the closed throttle position at rest