2004 C5 A4 + big cam: when driving in cruise mode the tranny upshifts nicely through all gears up to the 3-4 shift. After it shift into 4th everything seems fine then about 2 sec later the engine RPMs spool up 500rpms or so then back down, as if the TC unlocks then locks again. Anyone experience this? the fix?
Robert
What are your TCC apply/release values at? Also what are your 4 -> 3 values at? Did you change anything else? What did you change and what were you trying to do?We would need more info before we can actually help.
The only changes I made to the Tranny tables were to both WOT shift speed vs shift tables and both WOT shift RPM vs Shit tables. No other changes, not even to TM (customer's preference; wants stock driveability when crusing, daily driving, slow traffic, slow driving). I could email the latest file if willing to take a gander at it? Thanks in advance.
Robert
I just noticed you said BIG cam in an A4, how big? The VCM could be detecting false misfires, see what the log has to say about that ... is it detecting misfires? If so, the misfire detection needs to be tweaked or eliminated. Misfires will cause the TCC to unlock ... to many and it can put the car into limp home mode and stuck in 2nd.
230/234 .600 113 +4, stock 2.73s, stock TC
All my scanning shows just fine. Tech 2 Misfire tests all good. No misfire. This 'unlock' only happens 1-2 sec after the 3-4 shift under light load cruising. RPMs blip up 500 or so then back down, just as if TC unlocking then locking. This never happens at any other time during cruising or PE.
Thats normal, the vcm unlocks the converter during upshifts to protect the damper springs in the tcc. Stock settings are so mild you usually can't feel it.
It can be prevented by disabling lockup in third.
Or if you had a good converter you could set it up to stay locked up through the shifts.
That cam and 2.73's with a stock converter? Wow what a waste. Whatever.
AND it still has stock TM. Someone doesn't know what they're doing.
customer says he never felt this before when car completely stock. So, the big cam is amplifying this condition?Originally Posted by JasonB
I will try to disable lockup in third.
Customer is doing mods a little at a time, as money allows. He knew going into this that the cam is a mismatch with stock gears/TC. Doesnt matter since he's always planned for gears and TC swap down the road. In fact, he's got a 3200 TC and gears ready for me to install once I have an opening in the shop schedule.
Thanks for the inputs.
PS- this cam and UD pulley only swap + SD tuning yielded 85rwhp gain and 9mph gain in trap speed at strip, no other changes (stock gears, stock TC, stock 4 cat exhaust). Before I did this cam and pulley he had a Vararam yielding 315rwhp and 106mph traps. After cam/pulley/tuning he was at 400rwhp and trapping 115+mph. Not bad for 'someone not knowing what they're doing' as JasonB put it above....
Not bad for 'someone not knowing what they're doing' as JasonB put it above
Read that one post, it says big cam, stock converter, 2.73 gears, stock torque management.
thats all I read, does that sound like a combination someone who knows what they are doing runs?
Turns out with SD tuning even this cam is small. Cam works well even with the stock 2.73s and stock TC.So if one wished to maintain their stock drivetrain, I would even consider this cam on the small side now. The car screams with this cam, even though stock TC and gears, TM still on. I am installing an even bigger cam as we speak into a customer's 04 A4 Corvette that also has his stock TC and gears. Cam is 234/242 .610 113. Should be interesting....
The TCC unlock shortly after the 3-4 shift under light throttle is normal. It’s a slip test and I don’t recommend deleting it.
With a firmer TCC apply its noticeable.
With the stock settings, you would just see the converter slip without feeling it.
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