Very odd 47re shuttle shift problem.

Bustedknuckles

Bustedknuckles

Honey Badger
Joined
Jul 24, 2009
Messages
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So i have been chasing a shuttle shift issue on a customers 01 cummins with a suncoast trans for quite awhile now and decided to try asking here for some help. Around 45 mph it will shift 3-4-3-4-3-4 (commanded to electronically, not a mechanical issue) which as most of you know is a normal problem for these trucks and is normally easily fixed, however this truck is a nightmare! I have scoped the alternator output for AC ripple, it is perfect, installed a timbo APPS, spliced into the ground at the APPS and grounded it inside at the base of the steering column, cleanded all the block grounds including the one behind the starter, installed a noise filter, cleaned the connector right behind the RF wheel and the connectors on the trans, replaced the output speed sensor and rear diff speed sensor, cleaned all the battery terminals, etc with no luck. My boss has been a diagnostics guy for 20+ years and he decided to take a crack at it as he has more time to dedicate to it than me and he started by scoping all the wires at the PCM, they were all good so he moved on to the ECM and here is where we finally found something!!!! When he is viewing ECM data with the Modis the shuttle shift issue goes away completely! He was starting to backprobe and scope all of the pins at the ECM but the customer needed the truck back to push snow so we sent it out the door. Anyway, sorry for the novel but does anyone here have any ideas what could be going on here? :pop:
 
Could the scanner have somehow backfed a ground to the ECM? Just a wild guess, as I don't have them fancy tools... Does it directly read CAN off the Cummins DATA plug in the engine compartment, as I believe that has a faster baud rate & may give the ground to the ECM.... Sorry for the ramblings.

Ed
 
I went thru this about 2 years ago on a customer truck. Long story short I adjusted the tps and it has been good since. I know it's a no no but it worked. Would lock up around 50 instead of 45 and holds. Hope this helps.
 
Last edited:
yankneck696 said:
Could the scanner have somehow backfed a ground to the ECM? Just a wild guess, as I don't have them fancy tools... Does it directly read CAN off the Cummins DATA plug in the engine compartment, as I believe that has a faster baud rate & may give the ground to the ECM.... Sorry for the ramblings.

Ed
Click to expand...
That is what we are suspecting at this point. It reads through the OBD2 port.
RyanH said:
I went thru this about 2 years ago on a customer truck. Long story short I adjusted the tps and it has been good since. I know it's a no no but it worked. Would lock up around 50 instead of 45 and holds. Hope this helps.
Click to expand...

That may be what we have to do. Why is it a no-no?
 
I have been having the same issue. If you run 40 mph it will shuddle 3-4-3-4-3-4-3-4 but if you slow to 35mph or go on to 45mph it doesnt do it. Any updates from the guys above or any ideas where I need to look??
 
my 3-4-3-4-3-4-3-4 problems was caused by a bad governor pressure solenoid in the trans changed it out problem solved been goin on 2 years now
 
We put a new gov pressure solenoid in, the customer just took it and deals with it because he cant afford the downtime this time of year
 
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