I just recently rebuilt the thansmission in my dads truck at school. when we got it rebuilt and put back in my teacher said to put Mercon in it when the manual says to use Mercon V. is it ok to run regular Mercon in it? the transmission is a 4R70W out of dads 01 SuperCrew.

 

No, you must use Mercon V. I doubt you can find old regular Mercon any more anyway.

 

i mean the mercon/dectron III. so that stuff should be taken out and put Mercon V in? whats the difference in the two and why do you have to use Mercon V?

 

I would switch it out as soon as possible. I am not sure what the difference in the two is chemically but one is designed for your truck and the other is not. You may be able to get away with it for a while but why take the risk after all that hard work you just did?

 

mercon V is a synthetic fluid. You'll burn up the tranny if you leave in mercon 3

 

You can just about use any brand which says on the bottle that it meets or exceeds Mercon V specs. I have used Royal Purple, Lucas Oil, & Red Line.

 

it wont burn it up. they went to mercon V for emissions and oil life. Mercon III runs cooler due to it having less friction modifier on it.

 

so it is alright to run mercon/dectron for 10,000 or so and then drop the pan to make sure that i got it all back together right. im aint really got the heart to tell dad to spend 50 more bucks in ATF when i took a month, 3 trys, and 30 quarts of ATF to get it right...its a good thing im still a student in high school.:o

 

No, it is not all right to run non-Mercon V spec fluid. Do a complete fluid exchange.

 

I agree with glc. Get the right spec fluid in there.

 

Lubeguard makes a product to correct the friction modifiers. You could try that if you wanted to tide you over to the next fluid change. I don't really have much experience with it. The shop I worked for used it and never had any problems that I knew of. I was in a different building than all of that at the time however. The red lubeguard has always been good to me, the merconV stuff is a green bottle.
Alan

 

That is completely wrong.

First, there is no such thing as MERCON III. There used to be MERCON, then there was MERCON V. The difference is that MERCON V has anti-shudder additives. MERCON did not. If you use MERCON in a trans that should have MERCON V it will develop torque converter shudder and sometimes clutch shudder in about 20k miles.

So MERCON is fine if you don't mind having to rebuild the trans every 20k or so. If you want it to last use MERCON V.

 

Maybe he doesn't care!

 

??? ???

 

we went ahead and dumped a bottle of Lubegard Green in there. we will change the fluid in 10k or so and put Mercon V in there .