Transmission won't shift

[schneire]

I had my c4 transmission rebuilt by a local reputable transmission shop about 3 months ago, but am just now getting around to road testing it. The problem is it won't shift out of first gear on its own and the transmission shop went out of business. So, I'm stuck trying to fix it myself.

I can manually shift it to 1st & 2nd and it feels good, but as soon as I shift to drive, it goes back to first.

I have verified the kick down is not bound and working correctly. I have tried 3 different modulators, verified the rod, and direction of the spool, and proper manifold vacuum at the modulator. Shouldn't it shift at high rpms/speed even if the modulator isn't working. It doesn't.

I have not dropped the pan yet, but if I do, what should I look for?
Could it be a governor problem? I think I have to pull the transfer case to verify that, but not sure how to check it either.

I also read that sometimes just driving it will loosen it stuff up and it will start shifting. I drove it around the block 4 times with no change, but had to stop to work on a brake issue.

 

[Phil76]

When/if you drop the pan, make sure the bolts on the valve body are torqued. Had a similar issue, and I had forgotten to torque after assembly of the shift kit.

 

[DirtDonk]

Just on the off-chance.... Have you checked the fluid level already? Just wondering if when they filled it (or if you did it after the install?) it pumped fluid into all the little places and it was not then topped-off the final time.

If that happened, it would still normally shift I would think, but if it was borderline it might just have taken a few months maybe.

Just a thought.

Paul

 

[DJs74]

In addition to whats been said, make sure the filter is on tight. I believe the filter serves as filter and the "pickup". Also, do you know what fluid was used? The wrong fluid type might cause problems (old type ATF vs. modern type)


Good luck and sorry you are having trouble.

DJs74

 

[schneire]

In addition to whats been said, make sure the filter is on tight. I believe the filter serves as filter and the "pickup". Also, do you know what fluid was used? The wrong fluid type might cause problems (old type ATF vs. modern type)


Good luck and sorry you are having trouble.

DJs74

Fluid levels are good, I have topped it off a couple of times when changing out the modulator. I am using a Walmart Type F fluid in it.

 

[DJs74]

Type F is what I use so we should be good there.

Do you know what all the shop did on the rebuild? I'm thinking now about the valve body... if a shift kit was installed and there were springs / plugs / holes added, there could be something amiss there. They are not difficult but are tedious and the right spring rates and colors need to be installed in the right ports and if extra holes were drilled in the separator plate etc have to be right or there will be shifting problems.

Not trying to be doom & gloom, just being real based on what we know and how its acting. I think the first thing I would do is drop the pan and take a look at the valve body, filter etc and make sure everything looks good. You might have to drop the valve body and go back in it or take it to another shop and have them double check what the previous shop did in there. I think you'll find the problem and the answer somewhere in the filter valve body area.

DJs74

 

[DJs74]

I cannot find my B&M instruction sheet at the moment, was going to upload it for you.

Take a look at the link below. It gives a good overview of dis-assembly, modifications & reassembly for a C4

http://diyford.com/install-shift-kits-ford-c4-transmissions-step-step/


DJs74

 

[schneire]

I cannot find my B&M instruction sheet at the moment, was going to upload it for you.

Take a look at the link below. It gives a good overview of dis-assembly, modifications & reassembly for a C4

http://diyford.com/install-shift-kits-ford-c4-transmissions-step-step/


DJs74

This is one thing I wondered about. They did install a shift kit, but I don't know what brand they used. I suppose I may be able to tell when I drop the valve body.

 

[schneire]

Type F is what I use so we should be good there.

Do you know what all the shop did on the rebuild? I'm thinking now about the valve body... if a shift kit was installed and there were springs / plugs / holes added, there could be something amiss there. They are not difficult but are tedious and the right spring rates and colors need to be installed in the right ports and if extra holes were drilled in the separator plate etc have to be right or there will be shifting problems.

Not trying to be doom & gloom, just being real based on what we know and how its acting. I think the first thing I would do is drop the pan and take a look at the valve body, filter etc and make sure everything looks good. You might have to drop the valve body and go back in it or take it to another shop and have them double check what the previous shop did in there. I think you'll find the problem and the answer somewhere in the filter valve body area.

DJs74

The rebuild was more than a seals and clutches, but not sure how much... It was a rebuild to support 300hp, and still be warrantied. However, warrany is not much use now.... It does have a shift kit, but not sure what brand.

 

[56f100bbw]

C-4 Fresh rebuild with t -con on my 77 EB after 2k miles in 3rd it would slip to neu. Then back in drive change all fluid and filter took awhile to get it all to the full level .didn't help so my trans man changed the valve body yesterday and so far it's fine maybe you should do the easy stuff first change the valve body Good luck

 

[RajinCajun]

Is the vacuum line connected to the vacuum modulator. The vacuum line or the unit itself may be bad. Make sure it has good vacuum.

 

[lowbush]

Is the vacuum line connected to the vacuum modulator. The vacuum line or the unit itself may be bad. Make sure it has good vacuum.

It would still shift even if the modulator was shot it would just be rough.

I don't want to be doom and gloom either but I would be concerned about a transmission that came from a shop that can't stay in business. Most transmission builders doing performance builds are backed up weeks out and the really good ones are months out. I would be suspect of it. That being said these things are so simple that they probably just missed something in the valve body. I would see if you can figure out which shift kit they went with, get the docs for that kit and double check their work.

 

[Phil Munsterman]

Is there a reputable transmission shop that you could take it to just to get an opinion. A professional may at least be able to point you in the right direction. Phil

 

[Rustytruck]

Do you have the spool valve and spring that goes into the valve body and is held in place by the tab on the filter. That has to be in there and assembled in the proper order. Viperwolf had pictures of this assembly on this site at one time so you need to do a search.

 

[Bferrari]

How high of RPM are you taking it up to when in drive? The trans should still shift over 4K without the modulator.

 

[Bferrari]

Is there a reputable transmission shop that you could take it to just to get an opinion. A professional may at least be able to point you in the right direction. Phil

x2 - take it to another tranny shop, they may be able to get you pointed in the right direction.

 

[schneire]

I cannot find my B&M instruction sheet at the moment, was going to upload it for you.

Take a look at the link below. It gives a good overview of dis-assembly, modifications & reassembly for a C4

http://diyford.com/install-shift-kits-ford-c4-transmissions-step-step/


DJs74

I dropped the valve body this morning. Still not sure what shift kit is in it, but the separator gasket says transtec The separator plate is not drilled, but a check ball is missing.(the one that you would remove for a shift kit). This thing also fell out of the lower valve body when i turned it over... Not sure exactly where it came from.
https://www.dropbox.com/s/5s4mg43w3bxuiyo/2014-05-03 09.14.30.jpg?n=36301484

 

[74strokerbronco]

there is a line pressure port on the drivers side of the trans just above and forward of the shift shaft, usually has a square headed 1/4"plug in it . get yourself a good trans pressure gauge kit (buy/beg/borrow) and hook it up to that port and come back here with the readings in park at idle and around 2k, reverse with some load, drive or 3rd idle and load, same for 2nd, and first then well have more info to help direct you. this is what any good tranny shop will start with any way.

 

[74strokerbronco]

I see I was to late with that post sorry. can't pressure test tell you get the valve body back in ect. but now since you got the VB out find a good c4 repair manual and perform a full air test . the repair manual if it's any good will show you which ports on the case to air test.

I should warn you lol , since you ran the trans and it has fluid in it when you air test especially the front and rear servos expect some fluid spraying out. It can get messy and I suggest eye and face protection.

 

[schneire]

I see I was to late with that post sorry. can't pressure test tell you get the valve body back in ect. but now since you got the VB out find a good c4 repair manual and perform a full air test . the repair manual if it's any good will show you which ports on the case to air test.

I should warn you lol , since you ran the trans and it has fluid in it when you air test especially the front and rear servos expect some fluid spraying out. It can get messy and I suggest eye and face protection.

Well, I ran the air pressure test. I Could hear the clutches engaging, could see the band moving and could hear the governor growling.

The only thing I found on the valve body is that the separator plate was not drilled out. The rest of the shift kit mods were done.

Any ideas on what I can do next? Its not running good enough to take to a transmission shop and I really don't want to drop the trans again.

As to the early question about RPM's. I don't have a tach... But I ran 3/4 throttle for 1/2 a block and it did not shift even after letting out of it. Neighbors were not happy!!

I tried backing the screw out on the modulator a couple of turns and that did not help either... I also verified the modulator pin and spool were free when I had the pan off.

It shifts really good manually and holds tight. So, I think this means the bands and clutches are all good.

Is it a waste to drop the transfer case and check the governor, since its growling with air?