I am definetly going to get a FLT 4L65E Level 5 Transmission but I had 2 questions before I order. Should I get the 2wd Billet output shaft? Is it worth doing for my application? I also was wondering if I should do the Vacuum mod kit? What does it actually do and would it be worth doing for my application? Let me know because I need to get to get this new transmission so I can make a run at an 11 sec. 1/4 mile.

 

I recommend the billet output. Gonna take a lot of torque to get to the 11's. More than the stock output shaft might take.

The vacuum modulator takes all line pressure control away from the PCM. It is nothing more than a vacuum reference modulation valve that replaces the EPC solenoid in the transmission. An old school device that worked well for 40? some odd years in automatic transmissions. I recommend vacuum modulation. You will get others that say no. In my case I experience a couple 1-2 shift slips that I feel confident were related to the EPC. At the time I had a plug wire shorted to a header. I think the voltage given off by this screwed up the EPC control circuit. The only drawback I have with the vacuum setup is that it is difficult to "tune". If the shifts are to hard or soft you have to remove the pan, pull the vacuum modulator and adjust a pin length or play with the vacuum adjustment. Mine worked great full throttle but part and low throttle shifts were brutal. Come to think of it my current EPC controlled is same way and I haven't tuned it successfully yet either.

 

Thanks Alot for your help! Everything makes sense but now I need to find the additional $ for the Billet shaft output. I dont think I will get the Vacuum mod kit but that is not for sure, I have to think a little bit more about it.

 

I love my vac mod kit. I wouldn't have it any other way.

 

Why exactly do you love it? Is there any downside to the vaccum mod kit in your opinion? As I understand, the only downside to the vaccum mod kit is that it is hard to tune the firmness of the shifts because you have to drop the pan? Can you still use the tow/haul button to change the shift points? I am just trying to find every upside & downside before I make my decision.

 

The vaccum mod kit controls the line pressure to the transmission. Tow/Haul is still capable of things it was before except the engine vaccum controls the line pressure to the transmission instead of the PCM.

 

I would do the billet output, the price is steep but you will sleep better at nite... Thats why I got mine anyway.... As for vaccum mod??? Vaccum mod is the only thing I didnt do to mine, I personally like the control of the PCM but thats just me. I got all my shifts just like I want them.

 

If you can successfully tune shift pressures to your comfort with the EPC, have at it. A lot of people don't want to have to worry about pressure being an issue. I went back to the EPC, and tuned a bit to my liking.

 

While my truck wasn't broke again lol, i loved the vac mod.
It's a nice soft shift when driving around normal peddle, half throttle is quick but still smooth and not a jerk into gear.
WOT still feels like a smooth action just gets into gear like a champ.
Vac mod is a dream come true IMO.

 

You wont be able to set up harsher shifts in tow haul mode with vac mod. My trans was set up reall aggresive in tow haul and i like it. And the firmness is easily tuned. But whichever..