I have a 2000 4dr that I have done a mess load of work to. I am now noticing a whirring sound from the transmission. I have done a bit of poking around on this forum and it sounds like it is the pump. Looking at an exploded diagram it is behind the tourque converter and bellhousing. What my question is can the pump be replaced by removing the engine and changing it with transmission still in the truck? Reason I ask is, I was looking over the receipts and service records from the guy I bought the blazer from, and he had the tranny rebuilt because of a whirring sound and the shop that did it changed everything but the pump. The pumps are very reasonably priced on ebay and to get the tranny out I need to remove the motor mounts and lower the engine to get the top bell housing bolts. In my mind easier than removing the transmission in this circumstance. Thanks for your help.

 

You do not have to remove the motor mounts to get the transmission out. In my opinion, the transmission needs to be removed to do anything as precise as removing and reinstalling the front pump.

You may want to get the opinion of someone that knows these transmissions that can actually drive it to experience what you are describing.