Allison 5sp: rough 3-4 shift

[durallymax]

[YOUTUBE]WA_J87pxmuM[/YOUTUBE]

the video above shows it.

My truck seems to shift rough into 4th. at first I thought it was tuning and just that fact that it was fresh but now there is about 5,000 miles on it and i worked on the tuning tonite. It has improved a lot but is still rough.

Is there something internally I may have done wrong or should look at?? Or should I keep trying to work on the tuning.

 

[durallymax]

well i just watched the video again and noticed that during the burnout it shifter smooth.

To elaborate on these rough shifts it kind of rams into gear then feels like it slips or jumps out and then goes back in.

 

[Bentley]

3-4 is going to hit hard because of the added "bite" power of the C2 clutch pack. There is nothing that tuning will do to help it, but lots of miles and power will beat up the hard parts inside the trans. Also, the feeling you have when it hits that gear is because the driveline wraped up and is un-wraping to you get a little wa-wa feel out of it... It will smooth out at that tap cell re-learns but will never be "smooth"... Just be prepared to re-place some hard parts when you tear it down for a re-fresh! BTW, nice stack!!!

 

[TrentNell]

mine doesnt hit hard on the 3-4 shift ?

 

[beach_33]

mine doesnt hit hard on the 3-4 shift ?

X2

 

[Bentley]

To be honest, I don't know why some don't but I know mine would damn near knock your teeth out some times and would feel perfect other times. I cannot tell you how many times I would have the truck all sorts of crossed up getting on the freeway when it was raining because the 3-4 hit so hard that it would break the tires loose... Or get a nice chirp out of them on dry pavement... There are ways to reduce its harshness during assembly. But I built mine before there were ways to soften the shift...

There are 3 reasons this happens. The installation of the Transgo shift kit adds like ~50% more piston area (don't quote me on these numbers, Mike would know better) and the Alto's and Kolens have a higher friction coefficient and more surface area because you are adding more clutches due to thinner steels, which makes for a stiff engage of C2.

 

[GMC_2002_Dmax]

mine doesnt hit hard on the 3-4 shift ?

X2

Mine shifts great and I have a Co-Pilot as well.

 

[Righteyeblind]

mine doesnt hit hard on the 3-4 shift ?

Mine neither. It's because we roll the SCIII

 

[TrentNell]

Mine neither. It's because we roll the SCIII

i am still suprised i have not limped mine yet :rofl:

 

[Bako_Dmax]

OMG your stack is crazy! Dont plan on parking in any covered garages lol...

 

[Whitetail Addict]

A buddy of mine is having the same issue with his SCIV. It seems as though his trans is double shifting on the 3-4 shift.

 

[jonathancasey19]

whats the reason for the unique stack? just curious

 

[Kat]

A buddy of mine is having the same issue with his SCIV. It seems as though his trans is double shifting on the 3-4 shift.

When Wendy did the double shift thing, Pat moved my shift RPM up 200 iirc. It was 4-5 though.

 

[Whitetail Addict]

When Wendy did the double shift thing, Pat moved my shift RPM up 200 iirc. It was 4-5 though.

Kat, do you have to move the shift speed also?

My buddy had moved his shift rpm up....but not the shift speed.....3-4 is the only one that does it and that seems to be at wot, or close to it.

 

[Kat]

Kat, do you have to move the shift speed also?

My buddy had moved his shift rpm up....but not the shift speed.....3-4 is the only one that does it and that seems to be at wot, or close to it.

I will have to ask Pat when he gets home as I have no clue.

 

[JMDuramaxLB7]

Probably getting ready to pull indoors with a exhaust evac system attatched to the sled that requires a stack like that to go into the vacuum system.

 

[durallymax]

^^^ yep, it was actually the day after we got back and hadnt taken it off yet. Figured id drive around and get some funny looks. The normal stack is back on now.

I payed attention to it today, and it doesnt really feel like its internally, it feels like the trans slams into 4th but the the hole drivetrain torques like a soft tranny mount. I dont know what I just said, correct me if that makes no sense.

I guess since others are having the same things im not to worried. However i also noticed today it is taking its time completing shifts, could still be learning though. Ive been doing a lot of tuning as of late so it hasnt been on the same tune for very long.

I also noticed that every once and awhile it is a smooth shift. Not really sure why. It seems that If I am at WOT it is smoother through all shifts rather than part throttle leading me to think that i still have some things to work out in the tuning.

ill try raising the shift point. i need to anyways, when it shifts to 4th gear it gets under the turbo too much and will even bark it from time to time.

 

[Durasizzle]

my tranny kind of does the same thing but only when the torque converter is locked. if i hammer on it and have tow/haul on it will make a pretty good neck snapping bang.

 

[RENODMAX]

I have an idear on why a Suncoast IV bangs and I tweaked chads and seems to be fine. I have a beefed scIII in mine and it's fine. Honestly shifts best at wot.

 

[durallymax]

yes WOT shifts are smoothest.