Question : 4t45 question

[geldartb]

I noticed this a few months back when i finally got my tune to a point where it was safe to go WOT.

I use to be able to go well over 6k on a WOT shift and now im lucky if i can hit 5800rpm.

I know the 4t45 is weaksauce when it comes to handling more power than stock. now i have another transmission that is going to get the once over and beefed up but is there anything i can do to my current transmission on the car to help the problem.

I'm not getting any codes thrown or any weird noises from the transmission. i did pull the pan last year after driving it with the current setup and there were no chunks of metal or anything else just the normal amount of shavings on the magnet.

It still shifts fine and as of now there are no drivablilty problems with it. everything feels strong and it pull pretty good it just wont go past 6k. i have the WOT rpm's for the trans set high enough in the 6k range so that it should be shifting high but just doesn't.

I know the clutches are probably worn but i didn't expect them to wear this quick. the car doesn't get driven that much.

just looking to see if anyone has any tips maybe a servo or something wicked easy to fix or check.

I would like to hit the track and see what the car has in it but if im not going to be able to get the full potential out of it then i won't bother.

[ShadeTreeJack]

The 4T45 is not the cause of the sub 6k shift. It is calibrated for, I think, a 6300 RPM shift. Did anything get changed between when you could get over 6k and now cannot? with all the engine mods, I would expect more. Keep in mind; if your torque is falling off at higher rpm's there is no real reason to shift higher. Also Ive seen a 4T45 survive just fine behind a 3800 on a dyno.. oh darn, now I have to shoot you...no wait they can't fire me - they did that last year... how about a Pentastar can I get you into one of them? Maybe a Hemi? - I am still adjusting to my new work 20..

[geldartb]

you missed the part where i changed everything to allow higher revving shifts along with shorter shift times.

the cam has a powerband up to 7k http://i60.photobucket.com/albums/h5.../1357Large.jpg

the transmission timings and pressures are the same as before.

and a few runs on a dyno cannot be compared to hard driving for a couple years time.

[ShadeTreeJack]

Dyno testing for Durabilty

So you are now shifting at 7K? great.
a few dyno runs? oh no - no - 18,600 cycles consisting of several WOT accelerations and much more each cycle; designed to exercise the gears to 100,00 mile durability. not too real world for the clutches; very abusive and not enough actual applies definitely would shake out any defects though The T45 was derived from the T40 to handle the torque of the 3400. You may think of it as weak but it fit the market segment; small car, small engine, small trans, Very fuel efficient; we worked hard on reducing parasitic losses. helped GM get to many cars over 30 mpg. for mid size car; midsize engine; 4T65e... for large car, Northstar engine, 4T80E. a real beast for a FWD! it could handle a 5.7L but don't tell anyone. happy motoring. I am off to the Woodward Dreamcruise. Actually I have to replace a wheel bearing in my son's car..

[geldartb]

So you are now shifting at 7K? great.

no that's just what it is probably capable of.

[bszopi]

ShadeTreeJack: Would love to hear more input from you on the trannies. Looked at your profile, definitely interested!