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-   -   C4 Shift issues (http://www.hotrodders.com/forum/c4-shift-issues-228285.html)

kleen56 01-11-2013 10:48 PM

C4 Shift issues
 
I have a 68 C4 transmission on my SBF. I'm running a B&M quick shifter. Not sure where to look to fix my problem which is this. The transmission shifts fine when normal driving. If I put it in 1st gear and WOT, then click it to 2nd gear, it won't shift instantly into 2nd. If I back off the gas pedal, then it will shift hard into 2nd. If I stay on WOT, 3rd gear works fine. Is there an adjustment for this issue from 1st to 2nd with WOT, or what could be the issue?

joshp83 01-12-2013 09:52 AM

the band may need adjusted or the front servo seals are bad

rick 427 01-12-2013 05:59 PM

Another possibility...You might also want to check the carb to trans kickdown rod adjustment...if its adjusted to where its burying the KD valve in the valve body on WOT..then it would stay in 1st until you let up on the pedal,and in turn,relaxing that valve,allowing it then to shift into 2nd.

kleen56 01-12-2013 07:21 PM

I don't have a kick down linkage setup on my carb/ tranny. I'm going to try a band adjustment first. If I leave it in Drive, the transmission will shift OK, it's when I manually go to 1st (L), rev up the rpms and drop it to 2nd gear. It won't shift and continues to rev up until I release the gas pedal. Maybe a vacuum problem with the modulator valve? I don't much about trannies, but I think it may be something I resolve without a tranny shop charging me $ to look at it.:thumbup:

rick 427 01-12-2013 09:24 PM

Well then...I guess we can strike my last suggestion.....you offered up my next thought....I would 'T' the vacuum line to a gauge,and hold it in my hand ,and see what the vacuum is reading...you know the vacuum is right under normal driving,as the trans works good...but does something change under WOT?...and make sure ALL the vacuum lines under the hood,and at the modulator,are in good shape..Whats the history of this trans?...rebuilt,,stock,,never touched,etc.?

kleen56 01-12-2013 11:04 PM

Thanks Rick 427, The vacuum reads at 15 lbs at idle which should still be enough for the transmission. As for the tranny? I have no info on it, because it was the tranny that came with my truck. It appears it may have been rebuilt at one point or someone painted the casing Ford blue. It's been acting like this for some time now. Time to fix it as it's pretty annoying when you jump on the gas pedal and then have to back off to get it to shift:mwink: I like the C4, but may opt to replace it with an AOD. I've also noticed the problem has gotten worse after changing the rear gearing to 3.50 gears from the 2.80's that were in it. The engine screams, but what good is it if you can't bang 2nd gear?:D

rick 427 01-13-2013 12:20 AM

Well...you should really be seeing 18-20 at idle...15 is low.

joshp83 01-13-2013 01:41 PM

if you donot have the kick down hooked up it will not work correctly at wot


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