Engine or Transmission?

[soochan]

Hello, I've replaced 04 VQ35DE 4 Sp w/ 05 Maxima from LKQ online. For readers who are planning to replace your Quest engine w/ an used engine, my advice to you is you MUST open the front cover and check timing components! When my mechanic opened the front cover, he found the same problem, the chain guide, on the LKQ engine. Luckily, timing was not all messed up like mine, so, he only had to replace the chain guide. Another problem he noticed was plenum had a crack at a bolt hole closest to the power valve switch. LKQ refunded $150 and I ordered the plenum from TX at a price of $80. LKQ gave me 6 mo warranty. Here comes the question. So, my mechanic replaced the engine and working fine. No "Check Engine" lights up. One thing I've noticed was as I go up the hill, transmission disengages from OD and kicks down, engine revs up, but, speed does not increase (65 mph max). The van does not have "Gutts" any more. W/ original engine, my wife agrees that she was able to clear the hill w/ much faster speed and in faster time. Does anybody know how to determine if it's a bad engine or the transmission? Is there an easy way to find out? Thanx,

[quinnmueller]

You can usually feel a transmission slipping, engine revs but does not change speed usually points to the transmission. But you should feel the slip. If you haven't already I'd change the trans fluid, good to do every 50k anyway, and see if you notice a change. My van has power issues intermittent but mostly at idle and I can feel the engine missing on a cylinder, random misfire. Maybe look for vacuum leaks sine the manifold, you can check easily with a little propane torch, not lit, just turn on the gas and move it around the engine until you hear an idle change or not. Also try and take off quickly from stop, if it takes off quickly out shouldn't be the transmission, but the again, it could just be slipping in the higher gears.

[itinifni]

I believe that the cams are different in the VQ Maxima motor, than they are for the Quest's VQ. This is because the Max is lighter, and has less of a cargo requirement. While you might realize more horsepower with the motor swap, torque might be lowered because of this. Your transmission I believe is trying to do it's best to compensate for the difference. Is the intake plenum one from the Quest or a Maxima? If it's a Maximas, you might have better luck running the Quest's one.