C4 slipping in Second gear

[bronconate68]

I rebuilt my C4 400miles ago. At slow speeds, in drive, when it shifts into second, it will hold it for a few seconds then slip into a neutral state. RPMs raise, no power to wheels. All I do is let off the gas then give it more gas and it shifts down in to first.

If I manually shift it into second it also will slip out after a little while. It wont hold the gear. I rebuilt with the B&M kit that is suppose to be a manual/automatic valuve body. So I expect it to hold second. Is there a band that needs tightening? Some adjustment I can make?

TIA

 

[73stallion]

is the fluid level okay? sounds to me like it's low on fluid.

 

[bronconate68]

It only does this at really low speeds. I have taken it up to 3700 rpm is second before it shifts into third. If I go slow and it shifts in to second and I give it gas it will hold second until the rpm rev up or I let off the gas, then it shifts.

This is just happening at low, slow speeds.

 

[bronconate68]

fluid level is good. Checked and rechecked. I have the larg B&M transmission cooling fan and the larger pan. Fluid capacity is good. There has to be something to adjust, at least I hope.

 

[bannind]

Vacumn Modulator?

 

[bronconate68]

I sure could use the help

It is a new modulator. I adjusted it about 3 turns. The trans still shifts hard.

 

[BwoncoHowie]

It is a new modulator. I adjusted it about 3 turns. The trans still shifts hard.

Question: at what roadspeed does it shift into second when it spins-up as if it were slipping?

Try adjusting your front band to 1 1/4 turns, if that doesn't work, it may need a longer modulator pin.

 

[Gummi Bear]

Mine did that when the engine lost compression. Rebuilt the silly tranny twice, then realized that the motor was no bueno...

 

[bronconate68]

Thanks BwoncoHowie!!

I will adjust the front band, or at least check my original adjustment to see if I can tighten it.