Struggle to get truck to move when cold
My truck is a 2002 Ranger V6 3L Automatic Transmission with just under 70k miles on it.
When you move the truck from Park to Reverse, or Drive, you can feel it move into gear. When I let my foot off the break the truck just sits there. After giving it some gas and revving the engine up a little a loud thud is heard from the back end and the truck finally moves. It doesn't have problems shifting when going down the interstate (another problem cropped up at the same time and is described below), or after the initial thud.
The thud problem started today (first really cold night/day in Iowa), and is uncharacteristic of the truck.
Second problem (after reading forums, leads me to believe the alternator is to blame): When the truck hits ~4000 rpm the battery light flashes on, and the battery voltage drops to low. I had an employee of Advanced Auto Parts run a diagnostic to see if the Alternator is going bad, the test came back fine but the Amps pulled during the headlight and air on max test were borderline problematic. I purchased a new alternator and will install it tomorrow.
I believe the two problems are a coincidence and am hoping a new alternator will fix the second.
As for the first problem, what do y'all suggest I look at?
- The transmission fluid level is fine, but has never been changed to my knowledge.
- I had rear differential changed about 30k miles ago due to leak.
- Problem only occurs when the engine is cold, when warm it shifts into drive/reverse fine.
- Sound comes from back of truck.
Thanks for any advice and help you can offer.