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C4 Auto Transmission Issue

TX-ZACH

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Sep 27, 2021
Messages
131
Just cant catch a break. Bronco came back from paint (towed). Came off the trailer ok and into the garage for installing all the bumpers, interior, lights etc. After getting everything installed I was going for the 1st cruise up to put fuel in it. Once I hit 2nd gear it went to slipping.

Paint shop did replace a cooler with new brackets and not sure what could have happened other than maybe the put the wrong to refill from loss of cooler replacement.

Asking for advise or things to check before towing it back off to sit in another shop... Wondering if I should have it flushed with Type F and see if that brings it back. No issues prior to going to paint.
 
Joined
Dec 15, 2019
Messages
40
Band adjustment for 2nd is accessible externally . Adjust front band , snug mildly then back off 1 to 1 1/4 turn and tighten locknut .
 

Yeller

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Mar 27, 2012
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Loc.
Rogers County Oklahoma
Incorrect transmission fluid won’t cause a slip, however low fluid will. So will an out of adjustment band but if it was working before, check fluid.
 
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TX-ZACH

TX-ZACH

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Sep 27, 2021
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I checked fluid and it was 1/2qt low. I leveled it off. 1st and Rev is good, 2nd is all slip.

I inspected the band adjustments and were all painted with the cab off. I have yet to adjust the bands.
 
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TX-ZACH

TX-ZACH

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Sep 27, 2021
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I adjusted (hopefully correct) band located driver side front bottom. I tightened until snug and backed out 1.5 turns out and locked the holding nut. Road tested and no change. Are there any vacuum lines to servo's or control mods to check?
 
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TX-ZACH

TX-ZACH

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Inspecting for vac lines I found it was disconnected at rear of trans on vac modulator and i followed it up and also disconnected going into engine well. Further inspection I found no nipple or connecting hose off port where PVC valve is (3-port union). So the trans has no vac at all right now.

I will need to make a trip to auto store for coupler and more vac hose to make the connection.

Does this make a difference on shifting?
 

Slowleak

Bronco Guru
Joined
Sep 12, 2013
Messages
3,450
Inspecting for vac lines I found it was disconnected at rear of trans on vac modulator and i followed it up and also disconnected going into engine well. Further inspection I found no nipple or connecting hose off port where PVC valve is (3-port union). So the trans has no vac at all right now.

I will need to make a trip to auto store for coupler and more vac hose to make the connection.

Does this make a difference on shifting?

Yep… a lot of difference if disconnected.


Sent from my iPad using Tapatalk
 
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TX-ZACH

TX-ZACH

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Sep 27, 2021
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This is good news. It was disconnected at both ends. I stopped by the autoparts this morning on the way into work. I will connect up when I get home. It was running a bit rough but thought it has been sitting for a couple of months. I will start checking for other vac leaks and disconnects.
 
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TX-ZACH

TX-ZACH

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Sep 27, 2021
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Replaced and connected vacuum lines to manifold vac and modulator on back of trans and adjusted the band on driver side 1.5 turns in. Not only is it shifting in all gears it is also now firmer and a shift points higher in the rpm. Success in all categories. Cant thank you guys enough.
 

DirtDonk

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Nov 3, 2003
Messages
43,139
Double check your PCV valve. It should not be connected to a vacuum tree in a single runner on the intake.
Only the vacuum booster can be there in addition to other accessories. So any large fitting on a vacuum tree for a bronco is for a brake booster, if present.
The PCV valve is always to a common Plenum area either on the carburetor itself or in the case of factory valves the spacer plate.
 
Last edited:

reamer

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Mar 20, 2008
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1,152
Why in it called a PCV, (positive crankcase vent) when it is a vacuum, Shouldn't it be a NVC, Negative crankcase vent?
Positive "pushes"
 

DirtDonk

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Nov 3, 2003
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They weren’t referring to the actual pressure applied. They were differentiating it from a passive crank case ventilation.
Back in the day that could be just a vent, or a road draft tube, or the more effective exhaust driven evacuation type.
Positive just meant “active“ or something similar perhaps?
 
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TX-ZACH

TX-ZACH

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Sep 27, 2021
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Double check your PCV valve. It should not be connected to a vacuum tree in a single runner on the intake.
Only the vacuum booster can be there in addition to other accessories. So any large fitting on a vacuum tree for a bronco is for a brake booster, if present.
The PCV valve is always to a common Plenum area either on the carburetor itself or in the case of factory valves the spacer plate.
Good catch. The PCV was on a tree off intake and break booster on carb. I reversed those just now. Thanks for the that.
 

DirtDonk

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I’m glad you ran down the details so clearly before. Made it easy to catch.

You might have to readjust the idle and stuff like that, but it’s worth a little extra work now to keep it running the best it can.
 
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