I recently purchased a 1990 Volvo 240 DL (106k miles) that has been sitting for 3 months. For about a week, the transmission was fine, but then started struggling to accelerate for several seconds while the car slightly decelerates. I have to let off the gas and give it some pressure again in order make the the car accelerate or maybe catch the next gear. This usually happens from 10 - 20 mph.

I stopped driving it after this issue and checked the ATF level, which was good. I opened the filter pan that drained out about 5 quarts of ATF. The fluid was not black, but almost a dark brown with no burnt smell, and there were no metal flakes or big particles in the pan or the clean filter. I don’t think it’s ever been changed. The magnet had a thin layer of fine metal specks, which is normal for a used transmission. I assembled the transmission pan and filter back on but I didn’t want to put in clean ATF and possibly make it worse before I ask you all what I should do.

Since the filter was clean and there was no big or metal particles in the ATF, is there really any damage beyond improvement of the transmission’s performance? Am I at the stage where the transmission is barely starting to cause damage and might be safe to replace the ATF with a mix of Lucas Transmission Fix? Maybe the car sitting for a few months (and most likely more since it has low miles) may have caused buildup of some sort if that’s possible? For the record, I’m not a seasoned mechanic and have much to learn so my judgement may be way off.

 

How about just the appropriate fluid instead of snake oil?

 

Well this is the reason why I haven’t done any of these actions yet. If that transmission fix or any other product is not necessary, then yeah, I’ll just replace with only ATF. So besides that, you think a replacement or a flush of fluid would be ok in my situation?

 

Yes it's always a good idea to change to fresh fluids. Some have the idea that new trans fluid can make things worse in some circumstances, and that might be true. But IMHO continuing to use or not changing fluids could be much worse.