We are working on making some final adjustments to my nephews car before I let him take it out to drive. We just put a new modulator valve in his transmission which is a C4. In the test drives of the I have noticed a slight slip between 2nd and third gear. Is there away to adjust the bands in the trans to eliminate this little bit of a slip. Any help would be greatful. Thanks Allen Small
thats called ...flare...not much you can do to stock trans. to help. if there is..PaulS will be the man... mod/replace with after market valve body. ...frank...
you could tighten up the band but it is a bandaid fix the will probably hurt it worse in the long run. THAT is what I did... But I will be rebuilding the trans soon, and knew it when I did it.
The new modulator does have a small adjusting screw in the end under the vacume line. What turn ratio or what is the procedure to adjust the modulator? The car shifts fine but when you are able to wind it out and keep it pulling, but when you are just driving it around it does not seem to want to shift up to third gear unless you are up around 50 miles per hour and as soon as you let it drop in speed it down shifts into 2nd gear real fast. The car has a 3:72 rear axle which I feel may have some effect with it but I still think it should shift in third and stay in that gear for a while. We can actually ride around and never get into third gear if we stay at the speed limit. Thanks for your replies. Allen Small
check for ...vac. leak...on the mod. valve line... if good, play with the mod. adjustment screw. 1/8-1/4 turn at a time in/out. ...:Handshake...
The adjustment screw alters internal spring tension on the plunger diaphram. Under high manifold vacuum it tries to compress the spring and withdraw tension on the plunger rod to closes off two ports from mainline pressure fluid supply. Under low manifold vacuum, the oppisite happens. Try backing the adjustment out first.' The 3.73 gears has altered the overall operating relationships so you need to test settings until it's the best that you can get but should not hang up the shift and should reduce gear change rpm flare to a min. This procedure has an affect on the shift points as well as the govenor will try to shift earlier, with the lower rear gears. Every trans acts a little different. Make sure the kickdown rod and lever position is in a neutral position and does not have the kickdown lever partly operated. This is also adjustable for throtte position versus kickdown point. If you want to try the bands adjust, the intermediate band is at the left front of the case above the pan rail. Loosen the locknut and torque the bolt to 10 lb/ft then back off exactlry 1-3/4 turn and lock the nut up. The low/reverse band is on the oppisite corner near your new modulator. Loosen the lock nut, tighten the bolt to 10 lb/ft and back off exactly 3 full turns and lock in place. Good luck and let's hear how you made out.
Hey, Bluegrass, did you mean to say 1 and 3/4 turns on the front band? That is what the manual calls for, although I usually set mine at 1 turn.
My manual says the 1-3/4 (not a professional tranny manual, but Chilton's for the Maverick). I am running it at 3/4 turn because of flare I got after putting in my shift kit. Be nice to know that I am still running within specs...
Don't bother adjusting the modulator - it won't affect the flare. If the flare is during the 2-3 shift then your 2nd speed servo is releasing faster than the 3rd gear clutches can apply. If you didn't already you may need to rebuild the tranny but there are some checks to do first. Don't adjust the modulator - it controls part throttle shift timing and not the lag between gears. Adjust the front band. tighten it to 10 foot pounds and then back the adjusting screw out 1 1/2 turns. No tighter. Check the linkages. with the engine off and the throttle linkage held at wide open throttle. Push the "kick-down" linkage all the way toward the transmission and check the gap between the linkage and the adjusting screw. Adjust the screw so there is .060" gap. Check that the linkage between the shifter and the transmission is properly adjusted. Put the transmission in Drive with the engine off. Disconnect the linkage at the transmission and check that there is a perfect fit between the linkage and lever with the shifter held toward 2nd (but still in Drive). If it is not a perfect fit then adjust the linkage to make it a perfect fit. Drain the transmission fluid and fill it with type "F" unless you have already done so. You don't want anything more special than type "F" - it is the best fluid for a stock C4. After making these adjustments if you still have a flare on the 2-3 shift then you can try replacing the front servo and servo piston assembly with a larger one and / or rebuild the transmission to replace the seals on the direct clutch apply piston. An intermediate fix that is well worth the money would be to install a TransGo 40-2 reprogramming kit. It will eliminate most 2-3 shift flares and give you the ability to shift the transmission with full manual control or let it shift automatically depending on your mood. This is something you can do - the directions are plain english and it requires no special tools. If you need any further help just post and I will do what I can for you.
