Cummins Engine ISX 475 , 920000miles, oil pressure 38psi at warm prior to changing the main and rod

Cummins Engine ISX 475 , 920000miles, oil pressure 38psi at warm prior to changing the main and rod bearings. Decided to change main and rod bearings to increase the life of the engine.

After the bearings were replaced oil pressure went down to 28 ( noticed this as soon as I took the truck from the shop). Truck is running only Midwest , no hills no heavy freights

I called the shop the same day but was told to run it like this for awhile and if the problem does not go away I can go back. After driving the truck for 9000 miles, I decided to change the oil and all filters hoping that the pressure will come back . Unfortunately this did not happen at all.

Now the shop does not want to fix the truck telling me that its not their fault .

 

Shop did not change oil pump because it was ok.( Never been asked if I wanted a new oil pump , however was charged $210 to remove the oil pump) I was also told that the original bearings were ok no wear....but anyway they changed it.I spoke with Cummins Customer Service on 05/06/2015 , JX Peterbilt , and couple of more mechanics , some of them told me that the problem is most likely the oil pump , but as I said I did not have a problem with the oil pressure prior to changing the bearings.

 

If its not an oil pump , is it possible that they did not do the bearings correctly thats why the oil pressure went down instead of up . I am just trying to figure it out , since the shop does not want to take responsibilities .

 

When I called the shop, I told them that even after driver 9000 miles and changing the oil the oil pressure did not go up. The guy statement was: What do you expect your truck has a 1000000 miles on it. He was very rude , did not let me talk to the owner or the mechanic who worked on my truck. He also said: You did not changed the oil pump...........but his statement was different prior to taking the truck from the shop .......He told me that the oil pump was ok thats why they did not changed it ........
Someone did mention to me that maybe that shop did not put back the oil pump correctly.
I am so upset because, I spent good amount of money for this repair ...........trying to extend the life of the engine ( even though I did not have any problems )

 

Thank you
The job has to be redone ................which a good shop will not let it happen.