I just aquired a nice 96 D1 that had been mildly neglected by it's previous owner. The transission fluid was about 3 qts low and now that it is topped off with no sign of a leak, I am still experiencing a late shift from 1st to 2nd gear. It shifts at about 2900 rpm. all of the other gears seem to shift properly. Any suggestions as to what could be causing this or how to proceed with diagnostics would be appreciated. Thanks

 

Oh yeah it has about 150k miles

 

Did you follow the fill procedure? It's not as simple as just pouring ATF in. Sometimes the kickdown cable needs to be adjusted. Other times something internal is worn out and needs to be rebuilt. Rebuilding a 4HP22 isn't too difficult.

More info can be found in the RAVE.

 

Have the filter changed and a professional flush done.
The passage ways inside the trans are dirty and restricting fluid flow.

 

On these transmissions, there is a cable from the throttle assy to the transmission.

Make sure that it is a little limp when the gas pedal is off.
If it is not, then the load factor transmiitted to the transmission is too high and it will shift roughly.

 

Having been 3 quarts low has most likely done some damage and merely adding fluid will not cure anything.
The fluid needs to be completely replaced, consider adding a bottle of Lucas tranny additive and as mentioned make sure the cable is adjusted properly.