C4 No 3rd Gear, No Upshift

Hi all,
I'm having some issues with my C4 that I haven't been able to figure out by reading past threads. Let me lay out what I've changed (the transmission shifted fine last November) and how it's acting:

• I replaced the modulator (w/ same green band)
• I've replaced the mod vac line (I have vac at the mod)
• I rebuilt my steering column (adjusted the shift rod according to Chiltons)
• Added a BC kick-down cable (and have since removed it)
• Rebuilt the transfer case
• Checked the AT fluid level

This is how the transmission is acting:

• Taking off from a stop in 'D' the trans is usually in 1st gear
• Continued acceleration in 'D' does not result in an upshift
• Shifting from 'D' to '2' results in a prompt, firm shift into 2nd
• Shifting from '2' to 'D' results in a shift to 1st gear

The trans was shifting fine last November when I tore into the truck, other than whats above I haven't changed anything in the trans. I've also tested the modulator with a vac pump and made sure the valve behind the mod traveled smoothly (the pin is there as well).

I'm open to any suggestion. Thanks in advance!

-Jeff

If you are absolutely certain that your kick-down lever isnt being depressed and you are sure the modulator system is installed properly. The next step would be to drop the valve body and take it apart and look for stuck valves. if nothing found there then look at the governor valves.

What's up with that scary avatar? ~BH~

BwoncoHowie said:

If you are absolutely certain that your kick-down lever isnt being depressed and you are sure the modulator system is installed properly. The next step would be to drop the valve body and take it apart and look for stuck valves. if nothing found there then look at the governor valves.

What's up with that scary avatar? ~BH~

Click to expand...

BH, I was hoping you'd chime in, thanks.

During the course of diagnosing this is actually removed the kick-down arm (which made no difference). I forgot to mention though that I replaced the neutral safety switch but did not adjust it according to the manual - could this cause any shifting issues?

Regarding the modulator, it doesn't seem like there is much to go wrong here. Shifting behavior hasn't changed since I r&r'd the modulator valve and I have vac. Could the adjustment of the mod be causing this? The adjuster is currently set at 4 turns out - unfortunately I don't have the old adjuster any more.

Yeah, the pic is kooky. If you can't read the text it says "the forks...do nothing" - a play off of a Simpsons line.

Thanks for your help so far!

-Jeff

When you changed the modulater, did the valve come out with the pin? Putting that valve in backwards does wierd things.

I see it as either a modulater problem or a govener problem. If it bangs into reverse and drive real hard, modulator.

meckanik said:

...Could the adjustment of the mod be causing this? The adjuster is currently set at 4 turns out - unfortunately I don't have the old adjuster any more...
-Jeff

Click to expand...

4 turns out on the mod. will have no effect on your problem. 4 turns in could affect it some but still not be the root cause. You can test the function of your mod though by removing it along with the pin and hooking it up to a vacuum source (14-18 in.Hg.) other than the bronco with a missing modulator, in other words, dont start the engine with the modulator off of the trans. If the pin drops farther into the modulator when you connect it to vacuum (normally moves + or - 3/16"). Chances are you cant blame it on your new modulator. ~BH~

It looks like my reply last night got jacked. Anyway...

The modulator valve stayed in when I swapped mods and I bench tested the modulator that I have in there now so I know it works properly.

After driving the truck some more it started upshifting from 1-2, then eventually the 2-3 upshift started working. The trans was not dropping into 1st gear when taking off from a stop which I believe also points to a valve or the governor sticking. I'm going to drive it some more and possibly try a trans additive.

Thanks for all the help so far.

-Jeff

meckanik said:

BH, I was hoping you'd chime in, thanks.

During the course of diagnosing this is actually removed the kick-down arm (which made no difference). I forgot to mention though that I replaced the neutral safety switch but did not adjust it according to the manual - could this cause any shifting issues?

Regarding the modulator, it doesn't seem like there is much to go wrong here. Shifting behavior hasn't changed since I r&r'd the modulator valve and I have vac. Could the adjustment of the mod be causing this? The adjuster is currently set at 4 turns out - unfortunately I don't have the old adjuster any more.

Yeah, the pic is kooky. If you can't read the text it says "the forks...do nothing" - a play off of a Simpsons line.

Thanks for your help so far!

-Jeff

Click to expand...

Re: the Neutral Safety Switch... The NSS adjustment is a non issue for the problem you are having if the trans shifts into all the detent ranges D through L1.

I had the exact same problem when I rebuilt my tranny.. It was the modulator valve in backward. Here is a picture of the WRONG way to put it in: http://www.broncomarc.com/temppics/modulatorvalve.jpg

TTT.

I am having similar problems with my reman'd C4, and my transmission guy is away on vacation for another 2 weeks... Never noticed this problem unti last night when I took a test drive beyond my back alley.

The trans works fine in 1 and 2, but in D will not go into 3rd, it kinda seems "neutral"ish from 2-3 in D, off / on in 3rd. D starts out in 1 and shifts to 2 ok.

Trans is the C4, mild shift kit, all new soft parts, mild shift kit, new stock stall T/C. 35's and 3.50's (for now).

I will double check the kick down and vacuum modulator orientation. I am using fuel line to the modulator, could that be collapsing?

Thanks!

OK, I checked the kickdown linkage and the modulator has vacuum, have not removed the modulator yet, I did back the adjustment screw out a few turns and still no 3rd. Also no 1-2 shift in Drive, stays in 1 then kinda surgers to Neutral...

Any ideas? Thanks.

malcolmzilla said:

OK, I checked the kickdown linkage and the modulator has vacuum, have not removed the modulator yet, I did back the adjustment screw out a few turns and still no 3rd. Also no 1-2 shift in Drive, stays in 1 then kinda surgers to Neutral...

Any ideas? Thanks.

Click to expand...

Turn the screw in to where you started then about 3 1/2 turns more.

Thanks BH!

OK so removing the modulator to adjust the screw spews forth a fountain of $9 per litre Mobil synthetic ATF ( d-uh Malcolm %) ).

Went in 4 turns from where I think I started, still no 2nd in D or 3rd. I might bottom it out and see...

I have heard via the local EB grapevine that during rebuild theres a commonly missed problem in the valvebody on later C4's? At any rate, I aint droppin the pan at home, I'll either wait for my rebuilder or consult a shop.

It'a a bit of a bummer cuz it runs decent and is fun to bomb around in! Adults stare and children cry! ;D

OK, got some advice from another local rebuilder that my governor weights may be stuck, and also to try to back the modulator screw all out, reduce spring tension.

Any tricks for freeing the governor / valves with the trans in the truck? He said to drive it like I stole it, or better yet, to put it on jack stands and rev it up to speed as hard as I can.

I will put a magnet on the pan tonight too, trap any bits floating, but I tried to be very clean hooking the cooler lines up.

If adjusting the modulator doesnt change anything then return it to the original adjustment. It is probably not modulator related or your modulator valve is stuck. Other places to look besides the governor are the 1-2 and the 2-3 shift valves. The proper way to clean the governor is remove transfer case, extension housing and gov. valve assy. Then...

Governor Valve
If it is making 2nd gear starts while in D:
It could be the governor valve hanging up on a ferrous particle(s) imbedded in the governor body bores. Even a freshly rebuilt C-4 can have governor problems for various reasons, some of which can’t be avoided. Transmission coolers can get particles trapped in them from a previous transmission failure, and then release those particles when some new high detergent fluid that has been thoroughly heated goes speeding through there. Sometimes technicians loose or purposefully remove the governor filter screen, which is located in the governor feed passage. You access it by removing the governor assy. from the cast iron support. A missing screen can cause repeated governor failures. The cure for this is to find a clean governor screen from another unit. The C-5 also uses these same screens. In a pinch, a new nylon governor screen from a Turbo 400 works very well also. The C-4 screens are hard to find new any more but the turbo Hydramatic 400 governor screens are still available from your local transmission repair shop. If you are unsuccessful at cleaning the governor, you might try getting another assembly. If you have a problem governor, there is always pick-a-part or Ecology wrecking. There you can find a governor in better shape. I see cannibalized C-4's that you can get parts from almost every time I visit there. The drawback with the governor on a Bronco is that you need to remove the TC to access it. Both valves must move freely in the housing and return to position under spring tension. When servicing the governor, lube the assy. with ATF or WD-40, then torque the 4 bolts to 140 in.lbs.

Shift valves and particles
Valve body shift valves can cause shift concerns but this condition is not common unless something inside is generating particles. It could be the modulator valve or the shift valves hanging up on a ferrous particle(s) imbedded in the valve bores. What happens is when the trans warms up the valve bores expand a little and allow the valve to move freely and normal once again. This is because the spool valves are steel and the bores are aluminum. The aluminum has a faster heat expansion rate than the steel hence giving you a sense of normal operation when the valve body is warm. If you have valves continually hanging up it’s usually because there is a component in the transmission rotating assemblies generating particles. If this is the case, you will need a complete rebuild. It depends on what you find in the pan that will determine if the trans is in need of major service.

Kick-Down Valve
If this valve is stuck depending on what position the valve is stuck in could cause very late upshifts, or no downshift response to throttle related passing gear situations.
If the valve body was installed wrong, the internal kick down lever could be jamming the valve or even worse could be warping the valve body casting. If it is jammed it could also cause numerous issues because the valve body is not properly seating and sealing off the passages between the valve body and the transmission case.

thanks BH, much aprpeciated.

OK, its back, my transmission guy opened it up and found that he had forgotten to tighten down some side plates on the valve body, he says its coming back to him now that he took a phone call mid assembly. Happens I guess.

So now I have 3rd, but on his test drive he noticed that it shifts up to 3rd way too fast, he said he adjusted the vacuum mod where it needs to be, I have ~15" steady at idle.
He then found that my kickdown binds, he thought maybe my linkage was wrong - the ball stud on the trans lever has been welded in? But looking at pics on here it seems correct orientation... I have bent the kickdown back to what I think is as delivered but who knows after 30 years.

I had it engaging and fully depressing the kickdown at the last part towards WOT, but my trans guy says it acts as a TV(?) as well and needs to start depressing the kickdown earlier, he started to bend up the kickdown arm on my brand new TA, but I undid that and then did the screw adjustment as such, but now it bottoms before WOT and holds the throttle from getting to WOT, still upshifts early and doesnt kick down well...

I am also running 35s with 3.50s (4.56's soon), but the governor seems to work fine as it upshifts now.

I am gonna have to start all over I think.

So, the kickdown should only just fully depress the kick down arm at the last bit of throttle to WOT, correct? I will need to bend the linkage in a bit to accomplish this and still get to WOT, as the screw on carb kckdown arm is already bottomed out.

And upshifts are controlled by the vacuum modulator, turning it it delivers a later shift? Start flush with the end and then a max of 4 turns in?

Thanks.

OK, results after a bit of fiddling tonight.

Turned the vacuum modulator in 2.5 turns, its gettin deep tho not much left.

Upshifts are still early (compared to my electronic 04 Grand Cherokee HO), however if I'm matting it, it now holds 1st and 2nd up in the rpm's, and will kick down to 2nd now at intermediate speeds. I may not be gettin' to WOT with the accelerator anyhow due to the linkage to the pedal being too long, I will work on this...

The 2nd to 3rd shift is mushy, but my trans guy said it might take some time to break in...

Kickdown as is, is still bottoming before WOT, but I think some selective bending will get it to fully depress the kickdown, but still allow the throttle to get to WOT. And the kickdown return spring on the carb seems too long to return it as is (I bought the Holley "Ford" kickdown kit)...

So that tells me I'm headed in the right direction by A) resolving the pedal to WOT issue and B) gettin the kickdown to just fully depress at WOT.

malcolmzilla said:

thanks BH, much aprpeciated.

OK, its back, my transmission guy opened it up and found that he had forgotten to tighten down some side plates on the valve body, he says its coming back to him now that he took a phone call mid assembly. Happens I guess.

So now I have 3rd, but on his test drive he noticed that it shifts up to 3rd way too fast, he said he adjusted the vacuum mod where it needs to be, I have ~15" steady at idle.
He then found that my kickdown binds, he thought maybe my linkage was wrong - the ball stud on the trans lever has been welded in? But looking at pics on here it seems correct orientation... I have bent the kickdown back to what I think is as delivered but who knows after 30 years.

I had it engaging and fully depressing the kickdown at the last part towards WOT, but my trans guy says it acts as a TV(?)
as well and needs to start depressing the kickdown earlier, he started to bend up the kickdown arm on my brand new TA, but I undid that and then did the screw adjustment as such, but now it bottoms before WOT and holds the throttle from getting to WOT, still upshifts early and doesnt kick down well...

I am also running 35s with 3.50s (4.56's soon), but the governor seems to work fine as it upshifts now.

I am gonna have to start all over I think.

So, the kickdown should only just fully depress the kick down arm at the last bit of throttle to WOT, correct? I will need to bend the linkage in a bit to accomplish this and still get to WOT, as the screw on carb kckdown arm is already bottomed out.

And upshifts are controlled by the vacuum modulator, turning it it delivers a later shift? Start flush with the end and then a max of 4 turns in?

Thanks.

Click to expand...

Wrong, never on a C-4.

Correct.

&

Yes.

Thanks BH!.

Latest symptoms: In D, it shifts up from 2nd to 3rd way too fast, unless I drive it matt it... It manual shifts OK.

Have adjusted the vacuum modulator (lots of turns in, getting close to bottoming). I have to check the vacuum at modulator yet.

Governor if anything should be delaying shifts with 3.50's and 35's. Getting a bit frustrated.

I took the throttle pedal and linkage all apart and tweaked to ensure I was getting to wide open throttle.

I now have the Holley kickdown linkage and arm set to where, at the last bit of travel to WOT, it just fully depresses the kickdown, without binding the throttle arm travel to WOT.

And the kickdown return spring now stays snug, but does return the kickdown.

One thing I noticed on the Holley, which states its Ford kickdown equipped, is that the kickdown arm is spring tied to the throttle travel - it starts to depress the kickdown before the hard stop contacts the kick down adjustment screw - so not sure that that means? I'm gonna check the stock carb to see what it did (assuming its serviceable - the kickdown was disconnected when I got it).

I phoned my rebuilder with the latest symptoms. Because it manual shifts OK, he thinks its not enough pressure and wants me to check the stock carb and how it worked the kickdown, like a throttle valve... He still seems to think the kickdown acts as a TV... He also wants me to replace the fuel line with hard line for the vacuum modulator, and is looking at other modulators...

He's old school, doesnt' have the internet, the drag race guys here love him... But they shift manually...

I might have to get a knowledgeable 3rd party to test drive it and get another opinon.

Malcolmzial,
I have the same issues with my 77, took it to the trans shop late last week. I'll let you know what they say.