New to me trans problems

concretebone

New member
Apr 1, 2015
5
0
0
Hudson Valley, New York
Hello all, i just got a used trans and installed it in my truck (great idea i know) (a little back story..... First diesel truck, purchased it because my car threw a rod and i need something to drive.... just my luck i got a truck with tranny problems. so i went out and got a used trans thinking all is well, everything went good for the first 2 weeks....... and then)
all hell broke loose.

truck drives ok until it warms up and it will kick into 4th gear... not 3rd which confused me because limp is 3rd but it locks in 4th, and then i let it cool off and reset codes and it works fine......
the code for 4th gear incorrect ratio, as well as the occasional 5th gear incorrect ratio. i tried swapping valve bodies from my old transmission and cleaning it out but that didn't fix the problem (didn't make it worse either)

put a new output speed sensor.. didn't fix anything, also this only happens when the trans is past 150* and when i first start the truck it has to drive or rev i have to rev it and it slowly starts to move, my thought is sticky valves, but then i replaced the valve body with the one from my old trans that blew 4th.... i took it apart and cleaned it out first but the problem still is there.

also when all of this goes down at 150*+ i will pull over and restart the truck and then RD321 will blink.... i doubt its the NSBU switch and i checked all connections as well and the codes dont match up for nsbu ...... i have no other ideas. im from upstate New york and got the truck in CT

Ive searched the interwebs for days and now im posting because it is my last resort :mad:

truck info: 2002 lb7
industrial injection 75% injectors
batmowheel
airdog 2
dsp5 switch (keeping on stock setting until i get money for a suncoast)
K&N intake
ported intake elbow
Banks big head WG actuator

i just need to get to work and back ( im in a big situation im 19 and have a loan on the truck and a blown up wrx that i am pulling the engine to rebuild i just want this thing to drive right. since the day i got it, its been nothing but problems)
 
Last edited:

Mike L.

Got Sheep?
Staff member
Vendor/Sponsor
Aug 12, 2006
15,681
232
63
Fullerton CA
The trans output speed sensor is on the transfer case but the computer doesn't know it. So if there is play or severe wear in the transfer case it will give erratic signals to the TCM and show trans codes. You will need a professional scanner to monitor the turbine speed sensor ( on top of transmission case ) and output speed sensor on transfer case.