So I recently started having a problem with my truck not shifting into overdrive. I had a transmission coolant line leak that the mechanic originally thought was the problem. I got the lines fixed and coolant is full but it still won’t do it on its own. However, when I get up to speed and I let off the gas and give it a jolt, it will shift into overdrive. I was wondering if anyone could know what the problem could possibly be?

 

What engine/trans?

 

6.7L stock trans

 

I’ve never serviced it .. and I don’t know if the guy before me did. I didn’t know if the transmission is going bad or a filter needs cleaned or what exactly it could be

 

I have no clue what the 6.7 uses behind it.......