545RFE Info

[powderbrad]

Hey Guys,

Curious about a couple things regarding this tranny.

How high in 3rd gear can we run the HEMI? I noticed during my trinity 1/4 runs I need to shift to 4th going through the traps. Id like to eliminate this as WOT shifts to and from 4th are supposed to be terrible on these trucks.

Can I spin the HEMI to say 62-300 RPM in third rather than shifting to 4th through the traps?

Also WOT downshifts are hard and cause havoc on these trans. So, having a HEMIfever tune, a WOT downshift could happen with only about 50% throttle pressure, correct? Seeing as the throttle boost on the tune is ramped / engaging quicker? Maybe better way of saying it, is 50-60-70-% throttle pressure, is now 100% TPS % essentially...correct? And having a 60% or so throttle pressure would send a signal to the trans to go WFO and shift hard. therefore breaking stuff....eventually. (I try to disregard all this and manually shift if im driving hard, or thinking about passing etc.)

I was kinda playing around this weekend, did a few runs and ran a 14.4 @99 mph (fasters speed Ive recorded actually) shifting 4th. But ran a 14.28 holding third @ 88 mph (lol... I let off in fear of revving too high and coasted). Seems to me the 4th shift is killing my time.

So my ET was quicker, and had I held it long may have dipped to a low low 14 actually.

Advise...ideas? Anyhting?

Thanks,
Keep in mind our DA is like 4400, so all this equates to about a 13.6 at SAE

 

[Hemi450hp]

Are you shifting manually or leaving it in drive? I'm crossing the traps at 107-110mph with 28" tires and 4.56 gears, and I'm not in 4th gear yet. You shouldn't be anywhere close to 4th gear with your setup.

When shifting manually, the transmission actually shifts 1st-2nd, 2nd-2nd prime, 2nd prime-3rd, and then 3rd to 4th. The dash will show 4th gear when you are actually in 3rd when doing it this way. It is kinda confusing, but there is no reason that you should be seeing 4th gear at WOT with your setup.

 

[powderbrad]

My bad, 2nd prime I was counting as 3rd.

 

[Hemi450hp]

No problem. To answer your initial question though, I run my truck all the way up to 6800. I don't know how much I would trust that rpm with stock springs and no underdrive pulley though. You are pretty safe at 6400.

 

[powderbrad]

So I can hold my foot throught he floorboard shifting from 2nd prim to 3rd?

Also, if I just leave it in D, and hammer it, Im safe not to lift the pedal until Im through the traps?

I still feel running the 1/4 is rather hard on the tranny either way.

 

[Sillygoose]

Running down the track is much easier on it than highway downshifts

 

[Hemi450hp]

So I can hold my foot throught he floorboard shifting from 2nd prim to 3rd?

Also, if I just leave it in D, and hammer it, Im safe not to lift the pedal until Im through the traps?

I still feel running the 1/4 is rather hard on the tranny either way.

When shifting manually, you just need to bump the shifter from 3 to 4 at the top of 2nd prime. Be sure to have Hemifever send you a revised tune with a higher rev limiter if you want to do this though.

If you just leave it in drive, it will shift 1-2-3 and skip 2nd prime. Manually shifting will be faster.

And upshifts are perfectly safe on this transmission. Its the WOT downshifts that hurt the tranny. Upshifting manually at the track is safe as long as you shift on time.