Transmission problem WHen I put my blazer into drive it hesitates and then slambs into gear. I have checked my transmission fluid and everything and it is fine and 3 years ago when I got the car they said that they rebuilt the transmission, but now it just starting acting up. But when I drive it down the road it shifts fine. what could this be, do I need to get the transmission flushed?

When you say hesitation do you mean the engine will rev but the transmission won't engage

check the level of the coolant as milky transmission oil is water in the oil ( busted oil cooler in the radiator.) or water in the replacement transmission.

Read the owners manual for checking the Transmission Fluid. Usually it involves putting the car in Neutral and checking the fluid. If it is low, that could be the problem. If it is not, it may be a problem with the gears. I would take it to a shop to try to diagnose the issue.

Hi Don, have you checked the gear box oil level? Regards John

Did you get enough fluid in it? It can take several quarts and some drive test/checking fluid level to fill torque converter up. There is also a shift modulator (electronic I think) on those could cause that, or you got a bad transmission.

check the fluid level, if it is not low then change the transmission filter and put new fluid in it

check transmission fluid level, vacum leak.or wiring,transmission solenoid ,sensors. or hope not. bad tranny....eeecchh

You may have a bad revers solenoid. Check the fuse and look for any of the fuse to be bad like the transmission fuse. Best thing to do is get the blazer scanned at Auto Zone free of charge for any DTC codes that may be affecting your transmission's performance. Try this, place the ignition to the run position and pull the ECM(BATT) fuse out for 30 seconds and then place it back in. Start the Blazer, it may stall but let it. Just start it again the ECM is just relearning the engine and transmission, let it idle for 1 min and then go for a test drive. This should reset everything in the truck's ECM like the day it was first started and any DTC code will be new and active. Do not add any additives like lucas transmission fluid repair, that will just make it worst. Any additive that may the transmission thicker will make the fluid retention more making the shift solenoid stick causing shift conflicts. Good luck and keep me posted. No revers is ether a bad solenoid, bad PCM signal, or broken sun gear. 

Several things could be causing your problem:

1. Auto transmission fluid is low
2. Auto transmission fluid needs changing; this is an area that gets neglected by a lot of people;check the fluid and if its brown or gives off a burning smell, it needs changing. Very old transmission fluid will cause slipping in the transmission; if this is the case, it should be changed along with the filter

Hope you find that this answers your question. Best of luck.
Greg

p.s. If you have the fluid changed, make sure it's done from the tranmission pan, not through the filler tube; siphoning through the filler tube can be hazardous to the transmission, especially cars with a lot of miles

You are right. The transmission filter should be changed every 60,000 miles. While the pan is off for filter change, add one bottle of Lucas Transmission conditioner into the pan. Reinstall pan and refill with Dextron II fluid. Torque converter is OK.