C4 slips in 2nd?

[rednine4]

I just road tested my C4/C5 trans.. it hooks great in first and reverse. but when I got up to speed I was waiting and waiting for it to shift into 2nd and then it just revs up.


I just let out of it and parked it so I wouldnt do damage. The bands are adjusted to spec... 3 turns etc... so i am confident it's not them


kinda confused on this one... is it the vac modulator? or something else?

gonna start with the modulator tomorrow and hope for the best.. in the mean time any advice is apprcieated.

 

[Bent Bolt]

Yes , check the modulator and make sure the pin is in it too. Check for vacuum at the mod.

 

[rednine4]

So I changed the vac modulator and checked the vac line for leaks and it looks good. Test drove it and it shifts to second but very gradually.. Not sure what's wrong

 

[rednine4]

I guees what I am wondering is how can I firm up the engagement of the 2nd gear shift?? Is it possible that the bands may need to be tightened even though I adjusted to spec? my specs used were 10ft lbs and then backed off 3 1/5 turns for the intermediate band and then the reverse band was 2 turns...

I just installed the new green stripe vac modulator as it was out of the box... not sure if this needs to be adjusted or not?

 

[rednine4]

Anyone? I would like to get this fixed it's the only hold up in my v8 swap at this point....


It will go strong in reverse first drive but when it goes to second gear under any kind of load it just revs.

down the drive (downhill) it will shift ok but not very firm at all...

 

[projectnitemare]

I would double check your bands, from what you wrote you have the adjustments backward. The intermediate (front one) gets backed off 1 3/4 turns and the low-reverse gets backed off 3 turns. Try that first. If that doesn't work your next step would be to pull the pan and valvebody. Air check the drums through the case. if you get good apply and release then your problem is most likely in the valvebody.

Matt

 

[rednine4]

Are you sure? I read in the tech library under C5 dianosis figure 68A that it's 4 1/2 intermediate and 3 reverse.

I understand that the amount of turns differ from coarse threaded to fine threaded c4s. Mine would be the fine threaded (more turns).

http://www.therangerstation.com/tech_library/C5Diagnosis.html

 

[Bent Bolt]

It's about 3 to 3 1/2 turns on the intermediate. If still slipping , band is burnt , servo needs attention or both.

 

[rednine4]

Bands are brand new. I just cant see how it could be a band problem.

Right now i have the pan dropped.. the fluid looks good, I pulled the filter, now I am removing the valve body to do air checks.

 

[rednine4]

After pressure testing, everything checked out fine....


I will put it back together and see what happens tomorrow, although I doubt anything will have changed...

 

[Sighman]

When mine did there were multiple issues. The clutches where not done correctly and the spacing was incorrect when the transmission was rebuilt. The valvue body was in bad shape and even though everything tested out ok it still slipped badly and just got worse. I got TONS of help from this forum - http://www.fordmuscleforums.com/c4-transmissions/

I eventually just picked up a new one from TCI shipped to my door for $750 and wish I had gone that way first time!

 

[rednine4]

Yeah. I am leaning towards the valve body at this point. if it doenst work I will install an aftermarket VB... and if it still doenst work im going to give it a taste of my middle finger

 

[projectnitemare]

Is this a C4 or a C5? If its a C4 your intermediate is too loose. The tech article gives you the adjustment for a C5 intermediate (4 1/4 turns). All C4s I have ever done I have backed off 1 3/4 turns for the intermediate and 3 for the low-reverse. I double checked my books just to be sure that I wasn't remembering wrong. If you rebuilt the trans you could have issues with clutch clutch end play, total end play or any various other possibilities. If the valvebody looks ok and everything else check out I'm betting on the band adjustment.

Matt

 

[rednine4]

Good news. I pulled the valve body and poked around at the valves to make sure they were all working and moving freely. long story short I put it back together and it works like a charm!

3 gears, nice firm shifts, pretty damn scary to floor an 85 BII with a v8 in it for the first time.


I am guessing because I had the trans sitting in a basement with no fluid in it for a while that the valve body became frozen to some degree. Although nothing was visible, it's the only thing that made sense.


And thanks for the info on the band adjustments, I double checked my bands when I had it out and tweeked to spec as well.

Now I will be getting plates, insurance, and exhaust

 

[COPPERHEAD85]

And posting a video I hope...