Transmission Grinds Unless in "Sport Mode?"
 

I recently replaced my original transmission in my '90 accord dx due to it slipping, I put in an Lx trans. with supposedly 70k on it. To be short, driving in town sucks. The shifts are hard, up and down, and it will climb up to about 3k rpm until I can get it to shift up, regardless of what gear Im in. Then in 4th. the real problem shows up. There is an actual grinding noise that will happen if the car is in 4th. and the rpms are around 2k, so about the mid 40~s mph (90% of in town driving) unless I press the "sport" button and the grinding suddenly stops. Theres no codes getting thrown, but I have pulled both the nm/nc speed sensors and cleaned them up, but still nothing. I changed the atf fluid about a month after the swap it there wasnt much gunk on the magnet or in the fluid. So do you guys think I just got a bad replacement or is there anything I can do to avoid pulling this thing out in my drive way again?

Re: Transmission Grinds Unless in "Sport Mode?"
 

Not all codes will cause the D4/CEL lamp to illuminate.

Verify there are no stored codes. 9 NC will cause a D4 lamp, 15 NM will not.
Verify the sensor is within continuity.
Verify the TPS is functional.
Verify the throttle valve cable is properly adjusted.
Verify the fluid is at the full mark with the car warmed up and after charging every gear for a few seconds.
Verify the shift solenoids and lockup solenoid filters are not clogged solenoids are not sticking.
If there is only late upshifting the modulator valve may be stuck or sticking.
If you have not done a full flush of the ATF with drain and refill, do so. While doing this add a pint of TransTune or other trans cleaner(no leak stopper goos, only cleaners) at each drain and refill.

Re: Transmission Grinds Unless in "Sport Mode?"
 

check out ur warranty. if its short (30 days) pull that thing before its up. if not (1 year) the u could try and diagnose. no point of putting money in a already known bad trans. a lot of junkyards will give out returns first just to see if they dont return.