[gman2560]

My daughter has an 89 Mustang 4 cylinder with the 2 wire automatic transmission. A while back the transmission would not go into gear. We ended up removing that one and replacing it about 3 weeks ago with another used one (currently under 30 day warranty). After driving it for about 2-3 weeks this one now wont go into gear. Fluid is fine.

any suugestions on what to check? Thank you.

[dakine858]

Take a look at the transmission modulator on the transmission, there is a vacuum line running to it from the engine. Pull the line off and see if any transmission fluid runs out. If it does, you have a bad modulator and it needs to be replaced. However, if no fluid comes out, check to see if there is vacuum pressure to the modulator. If you find no vacuum, trace the line up to the intake manifold and check to see if its connected properly and make sure there are no cracks, kinks, breaks etc. If these things all check out, you're transmission will need to be rebuilt.