1992 Q45 transmission shifting problem

Greetings,
My son has a 1992 Q45 with around 98K miles on it. The car runs great, but the transmission recently started acting up. When the car is cold (like after sitting outside overnight), with the shift selector in "drive", the transmission lags some shifting into 2nd, then when it trys to shift to 3rd, the rpm jumps way up and the transmission feels like it went into neutral or back into 1st. If you manually select 3rd gear, it will usually go into 3rd and you can continue to drive. What's really weird is after the car warms up (say around 10 minutes), you can put the car back in drive and it will shift OK.

We decided to have the Infiniti dealer give us a diagnosis. They seem to think the transmission has an internal problem and suggested maybe trying to get a used transmission.

I don't really want to put that much money into this car and I'm wondering if maybe a flush/fill and trans filter replacement would be worth trying. And/or adding a bottle of Lucas transmission fix additive.

Does anyone have any suggestions or advise??? :frown:

Thanks,
Fujimo in Florida

No comments on fluid conditon appearance? No maintenance history for the transmission?

Problem is, you have a $50K car when it comes to parts or labor. No further discount beyond the discounted price you paid for the deferred maintenance.

Either you you have to pay up to catch up or drive it into the ground, which is probably what you are doing.