Built transmission and shift time?

[skintback]

What makes a high hp heavy truck with a well built transmission and good converter shift on time? Is that in the tcm/ecm tuning or does it have more to do with clutch setup and hyd's of the inner workings of the allison? I know a good lockup box seems to be important as well. I see/read that some of even the best built transmissions do not shift on time say your shift points are at 3500 and it's hitting 4000 before it shifts does this mean something is slipping converter/c1-4 clutches? or is the tcm/ecm part of the problem? Or is this somewhat normal? Just seems you loose alot of ET on the drug out shift times.

Just looking for good info maybe post up what yours actually shifts at vs set too when doing a 4x4 boosted launch and if lockup box/no box maybe even who built it

Mine is set at 3500 shifts at 4-4200 on a 4x4 boosted launch bens box i'm about 900hp 7300+lbs I put it together myself lol

 

[mike diesel]

My shift points are set to 4000rpm and it shifts on the dot every time regardless if i do a 4x4 boosted launch or not. My tcm has some lockup table tuning but with my loose 1053 converter, the tables don't work 100% all the time. So i rely on my BT lockup box at the track.

I built my trans myself and am making 800 wheel hp.

Mikes new shift springs make a big difference in shift quality and speed. If you don't have them In yours already, you will want to swap them.

 

[skintback]

Yes i have the ML springs they are a very nice upgrade thanks for your input.

My trans shifted on time before i added the 80 to the 66 now i do have old raybestos c1's that maybe my problem i will know what they look like this week

 

[mike diesel]

I am running all raybestos non slotted gpz's. What kind of line pressure do you have?

 

[CaptPhil]

With your kind of power it will never shift exactly when you tell it to. Mine shifts 300 to 400 rpm above the set shift points on all shifts except the 4 to 5. The more power you make the more it will blow past them. They aren't necessarily drawn out shifts, they are just later than you want. One way to combat this is to set your shift about 400 rpm below where you want it to shift.

 

[RHallenbeck]

I would imagine that it is "Rate of acceleration" related.. The RPM are climbing so fast that before all the actions can take place it has reached that shift point. Kind of like when you use a shift light as an indicator with a manual valve body. The reaction takes only tenths of a second but in the lower gears especially it can make 300-500 rpm over runs common on shift points..

 

[S Phinney]

Mine always shift on time. I'm over 1000hp probably 1200hp. My shift point is 4150 and is within 25 rpm every time. Only time I ever had a problem was bad c1 and c3. I got a set of the c1 rabestos that shed after initial setup. You know the story Sonny

 

[skintback]

I'm running around 320/330 for pressure. The problem i have is it did not do this until i made more power and yes i have given it time to learn. captphil you say that yours runs out passed gears 1-4 but hits right on the 4-5 because thats just how mine acts maybe everything is ok on the inside and the tcm can't keep up but then again you have some that do shift on time with big power idk i'm still trying to learn how everything works

 

[CaptPhil]

I have had more than a couple talks with evan about this, he said that it is very normal when running big power. Mike Graves truck has 3500rpm shifts set, but doesn't shift before 4200 to 4300. He has run in the 9s,so I'd say he is making some power.

I think that the lower your desired shift rpm is, the more it will overshoot. Even my stock truck was overshooting some until I raised the shifts up, then it started hitting them right on.

 

[Evan@InglewoodTrans]

Sometimes in high HP applications over shooting shift points then getting a normal shift a few hundred RPM later then commanded is common from what I've seen. However if your truck is actually starting the shift at your desired RPM and hanging it for a long period of time that is a different story. If your blowing through your converter you can have the same issue.

 

[Evan@InglewoodTrans]

Mine always shift on time. I'm over 1000hp probably 1200hp. My shift point is 4150 and is within 25 rpm every time. Only time I ever had a problem was bad c1 and c3. I got a set of the c1 rabestos that shed after initial setup. You know the story Sonny

What MPH have you trapped in the 1/4 or 1/8 mile running the 1200hp tune?

 

[Evan@InglewoodTrans]

I have had more than a couple talks with evan about this, he said that it is very normal when running big power. Mike Graves truck has 3500rpm shifts set, but doesn't shift before 4200 to 4300. He has run in the 9s,so I'd say he is making some power.

I think that the lower your desired shift rpm is, the more it will overshoot. Even my stock truck was overshooting some until I raised the shifts up, then it started hitting them right on.

With the latest TCM tune we tried set to 3600 it was shifting at 3900-4000 every time and if that trans is hurt it sure is good at hiding it for a whole lot of passes

 

[Mike L.]

Sometimes in high HP applications over shooting shift points then getting a normal shift a few hundred RPM later then commanded is common from what I've seen. However if your truck is actually starting the shift at your desired RPM and hanging it for a long period of time that is a different story. If your blowing through your converter you can have the same issue.

With the power we are running in some trucks; the calculated rpm X speed X proper gear that was programmed at the factory does not match and the TCM might be getting mixed up.

 

[S Phinney]

You got me Evan! It should be around that. You will be one of the first that I call though when I do.

 

[Evan@InglewoodTrans]

You got me Evan! It should be around that. You will be one of the first that I call though when I do.

Not trying to be a dick but the ass dyno is known liar and a lot of things that should happen generally don't when it's time to make a pass at the track.

 

[skintback]

good info.

Mine to me kind of feels like the converter but it locks pretty hard when it shifts into 2nd wot but i haven't logged it. it feels like the motor is revving alot and not going anywhere until i get into 5th

it's a new 1055

 

[IOWA LLY]

Log the tcm and watch for when it commands the shift. Change your "shift mph" up or down based on what you see it actually doing, and what your wanting it to do.

Shift mph is the primary table it uses. Shift RPM is almost ignored in my opinion. If your trying to use rpm instead of mph it will be sloppy. As you have found.


The speed of the shift itself is tcm controlled. No matter what is done internally to the transmission it will only shift as fast as the tcm will allow it to once it's learned in.

If it's shifting slower then the tcm desires then it's either a "learn in" or an internal transmission problem. (Can't hold the power)

 

[Muff]

Off topic - glad to see your back and posting good info Iowa :thumb:

 

[skintback]

So what you're saying is play with the D5020-5023 tables? what about the down shift tables D5035-5038?

 

[mike diesel]

I don't mess with the mph shift table. I use the RPM table only and it works perfect.