Well I just got my new heads/ cam/ pt4000/ 4.10 set-up dynoed and it put down solid #'s. On the way home I get on it from first gear and it shifted hard into second but would not shift into 3rd, just kept banging the 6800 limited (redline set at 6500). I then did a 2nd gear punch (~40mph), the car downshifted into second, and proceeded to shift into 3rd perfectly at around 6000-6200. These results kept repeating. So basically, when the car starts in first it will not do the 2-3 shift, yet when it downshifts into 2nd from a roll, it will shift into 3rd. I thought it may be a tuning issue, so I went to another well known tuner in town and we tried changing the mph and lowering the shift points with no luck. Its was wierd though, as all the commands once again worked perfectly in the downshift scenerio but not the 1st gear punch.

So I figure it must be mechanical. The only thing i could think of was that perhaps the 3rd gear plates were already in motion when doing the downshift thus allowing them to catch on the shifts, but i dont know. Whatever it is, I am aware it is th400 time (im going big anyway!) Any input would be appreciated though as i just want to know what it is. Thanks

Daniel

 

You said the comand wasnt right, Does that mean when looking at the data in the tuner that the 2-3 shift is not comanded when starting from first?

 

my car does the same thing..i started a thread awhile back and everyone said to lower the 2-3 shift point....thats weird where having the same problem..but my car is just full bolt ons ss3600 and gears(3.73), please let me know what happenes please

 

No, it was commanded correctly to shift like any normal tune. The second tuner commanded it to shift earlier to try and test the tranny- it only worked when I started from a roll to a 2nd gear downshift, just like it did before. It seems the tune is fine- but something is off somewhere as the tranny will only do a 2-3 shift from a rolling start above 1st gear, but not a 1-2-3 from a stop/ 1st gear punch. I hope that makes sense. Thanks everyone

 

Maybe you should try using a good driver

 

there should be no difference between a rolling start to a 2-3 shift and a dead stop to 2-3 shift, Very strange

 

that was uncalled for....how the **** would a different driver make a difference in it not shifting? its an AUTOMATIC!

 

I know, I helped swap the heads/cam in the car. I want to figure out this weird problem too.

If there is no difference at all regarding the 2-3 upshift from a roll or stop, would you say it is DEFINATELY a tuning issue, or could there possibly be a problem with the converter?

There was always a little hiccup on the dyno graph when it was being tuned, presumably from the clutch packs shuddering and then catching, however this was strictly in third gear while tuning (of course) When the tuner ran it through the gears on the dyno, there seemed to be no problem at all.

Could this possibly be caused by the extra strain on the tranny from trying to move the vehicle itself as opposed to rolling the dyno drum?

This has several people completely stumped. It would be nice to get a solid run or two in the car if the tranny is actually working fine and this is a tuning issue.

I keep going back and forth myself between tuning and tranny. The tranny has high mileage (100k), and the car is putting down serious power now for H/C which could possibly be more than the tranny can handle, but why would it only work from a roll? if it's going to slip, one would assume it would slip ALL THE TIME.

Could the converter have an impact on this?
Even if the tranny slips, shouldn't it still shift?

 

Dave (joker), you are a nOOb at Teh insults. But thank you for elaborating on the issue.

 

i have seen many 4l60s do this im interested as well i was always told that it was from the stock tranny?let us know

 

The weirdest thing about this was the car shifted perfectly on the dyno. I have a few ideas on what Im going to try to fix it. I'll post up the results when it's finished, hopefully with a fix.

 

Do you think that maybe line pressure could be the issue?

There's a transgo shift kit in the tranny. I'm sure Len put it in right, but if by some chance he didn't that could be causing a pretty big lack in the line pressure at WOT. Maybe that's why we were getting that hiccup on the dyno. An apparent drop in line pressure could be the #1 culprit for the slippage. Maybe if we tried bumping the line pressure if would work, but how long could the tranny pump last if we bumped it to like 250 psi, and with the shift kit in there, it's obviously tough to know where we'd be starting as it raises the pressure to a general, yet still unspecific point (especially if Len didn't put it in right). Yank doesn't recommend a shift kit with their converters anyways and he has the PT4000 in there.

What do you think Steve? Take out the shift kit and try bumping the line pressure with the tune?

But still, WHY THE HELL does it shift perfectly into third when it's a "passing gear" downshift? This is so weird that it's pissing ME off and it's not even my car!

 

I would be happy to discuss this issue on the phone. It is complicated and there is much to communicate back and forth.

Don't hesitate to call, I have a meeting inthe a.m. but should be available after say 11:00 a.m.

g

 

I have seen this a few times over the years, (when you are manually shifting) that when you take off in 1st and go through the gears it sometimes will not make the 2-3 shift, or when leaving it in the "D" position, then from a roll it will make the shift. The problem could be as simple as "low" fluid level, even though it might be reading correctly. Try adding a 1/2-2/3 of a quart and see if this fixes it. If it does, then the fluid level was not correct. Make a new mark on the stick for the new full level. I have seen this work more than a few times. Another test is to leave it in the "OD" position and see if it changes from the "D" position. If that solves it, now you know not to use the "D" position when racing it. This too has solved this problem more than a few times. You will not hurt anything by slightly overfilling the transmission.

 

If only it were that easy...

 

Well, Steve fixed the problem by increasing the line pressure and now it shifts very well. Thanks everyone

 

Glad to see you got it under control. I know we talked about an awful lot of different scenarios yesterday.

Any idea how much % above stock the L/P is now?

g

 

direct clutch pack is going away due to decreased line pressure. I would assume that the pump is binding and fluid volume it falling off.

 

but what about a stock tranny (not transgo)? my car statred doin it when it got cold out...i havent dug into it as i realy havent had time..but my car has a ss3600 a deep pan and a cooler as well as a tranny temp gauge..and it does the same as the OP it bumps the limiter 2-3 times on the 2-3 shift from a low roll and from a dig. but from say 50 it shifts fine.. should i try just increasing the line pressure on the 2-3 shift or all together. thanx and sorry for the hijack....

 

Im not sure the exact figures, but he increased them a good amount.

Slim- I would up the pressure, worst case is that is doesnt work and you lower it down again