I have a 93 Sonoma (4.3L) with a rebuilt 4L60E trans with about 20K on it. Sometimes i manually downshift if from OD to D if the engine is lugging in the low 40 mph's. As far as i know this is not bad for it but it's now making a noise when i do it... mostly a clunk. Wondering what the problem could be. It's still under warranty, so when i call i'd like to know more about what i'm talking about. Thank you in advance! I plan to check my u-joints to see if they're ok.

 

i'd check the trans mount if it hasn't been replaced as well as motor mounts, u-joint, suspension related components.

 

 

Now what happens when i downshift from OD to D is absolutely nothing. Anyone know what went to hell in it? Thanks!