Slight Grind when Shifting up into 4th gear

I do a lot of work on cars/trucks but not transmissions.

I've noticed in my 07 4.0 TRD Offroad - manual that there is a slight grinding when shifting up into fourth gear. Shifting down into 4th gear is ok. If I pause and let the engine spin down it helps a bit. All other gears are fine.

Thoughts from you transmission folks?

 

I just posted this link in another thread. It appears below. You may want to read through it as it is a very interesting account of some of the problems with the early 6-speed. You have an early 6-speed. For your truck you have not stated the miles on your rig or whether it is shifted vigoursly, or whether you have tried some of the different gear oils mentioned in a number of threads. Beware the transmission only holds a paltry 1.9 qts. and has no filter or internal magnet save a whimpy one on the drain plug. Its been my contention for a while that the transmission begs for frequent lube changes. Here is the thread:

 

Thanks for the reply.

150K on the truck and I'm not an aggressive shifter. I follow the oil changing schedule for the transmission as well. Maybe I should do it more often.

Lot's of people with different preferences on oil. What is your choice? I'm thinking RedLine.

 

Changed with RedLine MT-90 and seems to have cured the slight grinding. Going to put this on my every 2nd oil change or 10K schedule.