My C4 auto trans shifts at 1500 rpm, which means I hit third gear BEFORE I get completely through the intersection (3.80 gears). Isn't there a screw or something I could turn to adjust this up to shift at maybe 2500, or at least 2000? Also, if there is an adjustment, is it going to do any harm to the tranny to start adjusting it up like this? Finally, what would be a good rpm for shifts on city streets, considering that I shift while racing at 5000-5500?
Band adjustment in not used to change the shift points, only to take up band wear. Assuming your using a C4 auto, the shifting points are controlled by throttle opening that affects the intake vacuum the modulator senses. The trans has a govenor that gets into the act but really determins the hi rpm shift points when in auto or third gear position. The modulator 'if the right one' is adjustable, otherwise manuel shifting will have full control.
I adjusted mine by scewing the modulator in and out. Under light throttle in Drive I shift at around 4,000 (4.11's)(partial throttle I am in third pretty quickly) When I stand on it it will auto-shift at about 5200-5300 R's.
yeah.. the vacuum modulator.... take the vacuum line off the vacuum modulator... there is a screw in there with a flat tip screwdriver slot... turn it in to make it harder to shift, or higher rpms... take the screw outward to make it shift quicker.. lower rpms... hope this helps ya
Sounds easy, I will try to get under there this weekend and give it a try. I would like it to shift under light acceleration much higher than 1500. This adjustment won't increase wear or damage the trans, will it? Still stock trans, and I don't want to crater it before I get a chance to rebuild.
I hope it does something... Vacuum modulator...do I find this by just following the vacuum lines from the engine to where they go into the trans? I think it is a round item on the passenger side, right? Remove the tubes, and the screw is inside the tube? or what. Do I have to remove the round modulator unit, or just the tubes? To be honest, I have not looked under the car yet, and am just asking questions based on what I remember seeing under there. Just wanted a little guidance before I go cranking screws and such. Also, will adjusting one screw work for both gear shifts, or are there separate screws? On a different note, I just looked in the Haynes manual and found the converter drain plug. A couple years ago, I drained the trans and put in a new filter, but I know I only drained what was in the trans, not the converter. Will the converter drain plug drain all (or almost all) of the converter for a full fluid change? I might make a weekend of putting in a shift kit, finally replacing that worn o-ring at the shift linkage that has leaked on my floor for years, and messing with this shift adjustment screw. But I admit, the trans is the only part of this car that I am uncomfortable working on, since I don't know Jack Schitz about auto transmissions.
Put in your shift kit before adjusting anything in your modulator, as shift kits change shift points. Your modulator may not even be adjustable.
the way it is shifting is correct for a stock setup at very light throttle. should shift low. you might notice it a lot more if you have steeper gears in the car. install a good shift kit and an adjustable modulator. then you will be able to tailor the shifts a little better. the mod is on the pass rear of the c4 near where the extension housing bolts on. sometimes hidden partially by the trans crossmember. follow the vac line down the side of the trans. or if you dont want to do a shift kit, buy a street/strip valve body & bolt it in. if you want unbelieveable shifts, get a reverse manual vb, but you must shift every gear all the time & if it doesnt have band apply in first, it might bother you.
i thought you had a shift kit... ok... this is what i do know i had a stock shift kit in my car when i frist put the tranny in... it shifted as yours did.. grandma-style. i got my tranny rebuild and i had them put a shift kit in it.. all i can say is OMG... whip lash... i shift manually... using my shifter.. i never leave it in drive...so i dont know the shift points... but... when i shift from 1st to 2nd.. at about 4500 rpms... my back end gets a little squirrely... and i spin the tires a bit.. its pretty cool when i drive it hard... at the track its different..... with all the tire on the ground... when i shift it yanks me back into the seat,.... and i rarely get any tire spin when i shift into 2nd the shift kit make a HUGE difference in the way it shifts....night and day... im telling ya... the bet 140 bucks i spent on the mav.. dont bother with the modulator... get a shift kit.. i have been told that they are easy to install.. but i had the tranny shop do it when they built the car... so i cant tell you how to do it... but i would highly recommend it... you thought you were grinning when you put the heads on..? try the shift kit.. hehehe... i wish i could see the look on your face the first time out with it... i wish i could see a pic of me when i got on the freeway on the way home from getting the car after the tranny build... lol
$140??? I have been looking at a B&M shift improver kit for $60. Am I looking at the right thing? This is in JEGS (and Summit) and replaces the valvebody and you can set it up for snappier shifts. Or is your $140 including labor? Should I go with the $60 one, or would the $30 one be good enough?
the higher priced one (60) is a little more performance oriented if my memory serves me right, but either should work well. still get the adj modulator. i used the cheaper kit once long ago. worked fine. do the top choice in the kit. ive used both superior and trans-go kits, also. both worked well. for 140 you can probably buy a s/s valve body.
Do Not buy a B+M shift kit I`ve had personal expeirience with them and have also had 3 different transmission builders tell me they are Junk. They will give nice shifts at first ,and then the shift will get "softer" and softer over time. Also you`ll get the 2-3 "flare" after a while. I know this sounds fiunny but I `ve seen it happen several times with diferent people using the B+M kits in C-4 trannys. Go with a Trans-go,Fairbanks, ect,ect. My car has a Hipsters reverse pattern manual Valve body and I like it!
