Technical C4 playing up

Hi
following a motorcycle crash i've changed to a C4 using a flat o matic kit behind my flattie.
If i put it into drive or reverse there is often a delay and then it will engage with a bit of a clunk and lurch forward or backward.
i didn't fit it and now realise how little I know about auto trans
is this symptom common and normally something just needs adjusting or is it more sinister
Thanks
Neil

 

Was it a new rebuilt C4 or a used one?

 

How long of a delay are you talking about, 1 second or 5 seconds? If the rpm's are up (Say 1000 or higher) the trans will clunk and lurch.

 

I have a C4 with similar symptoms , but only happens sometimes , once a month or so , been like that for years. raise the RPMs and it responds. got me wondering why too.

 

Sounds like your filter is starting to clog.

Dawg

 

Other than slow fluid pickup issues, some of the clunk can be due to slack in the front yoke/trans output shaft splines having some wear and looser fit. Also, rear end slack......ring and pinion backlash, differential spider gear pin, spider gears, axle splines to side gear fit. It all adds up. Most common cause, I think, is excessive idle rpm. I'd look there first.

edit: C4 trannies have a modulator on the back of the case. I can't recall if they affect at idle gear engagement, but do affect upshifts for sure. In any case, be sure the modulator is connected to the manifold vacuum line and the modulator itself is not leaking internally. Check for fluid in the vacuum line connection at the mod.

Ray

 

I think band adjustment will help your issues a ton . High RPM is a killer on C4 bands . There is a small actuator that will bush into many pieces after a while of banging forward to reverse


Sent from my iPhone using H.A.M.B.

 

Here are the basic clutch/band engagements for each gear on a C-4. 1st gear, forward clutch and low/reverse band. 2nd gear forward clutch/ intermediate band. 3rd gear forward clutch and high/reverse clutch (sometimes called direct clutch. Reverse, high/reverse clutch and low/reverse band . You will notice that the low/reverse band is used to start forward or start backing up. You might check band adjustment, low/reverse servo piston, or low/reverse valve body components. On VERY light duty C-4s first gear used the forward clutch and low one way clutch (sprague) in first. But only Pintos and very light cars used that arrangement. I hope the info helps, good luck. A C-4 set up correctly, is simple, strong, and dependable as Lassie.

 

Simple thing to look at first; check fluid level

 

You may want to hang out here too! http://www.network54.com/Forum/260730