C6 shift point and kick-down adjustment
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Tuned
Joined: May 2005
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From: MI
C6 shift point and kick-down adjustment
I just bought a '94 Bronco that someone swapped the drive-train in from an early to mid '80s Bronco. I've never had a C6 before. Can shift points be adjusted? What about how to adjust the kick-down? I didn't see a kick-down cable. Is it just vacuum controlled? It doesn't kick-down at all right now.
Also, the shift points are horrible. It only goes into second at 35mph, no matter what, and downshifts to first when it stops. It only goes into third at 55mph, no matter what, and doesn't downshift to second until around 35mph. Also, the torque converter seems like it is locked in 2nd and 3rd all the time. Is that normal? It has a 2,400 stall converter installed and with the TCI pan on the bottom, I think it may have a shift kit, too.
With 3.55 gears and 33" tires, it does just over 3k rpm at 70mph, which I know is normal and I have no complaints. I just was wondering about the rest. The trans does not shudder or jerk. It engages very firmly.
Also, the shift points are horrible. It only goes into second at 35mph, no matter what, and downshifts to first when it stops. It only goes into third at 55mph, no matter what, and doesn't downshift to second until around 35mph. Also, the torque converter seems like it is locked in 2nd and 3rd all the time. Is that normal? It has a 2,400 stall converter installed and with the TCI pan on the bottom, I think it may have a shift kit, too.
With 3.55 gears and 33" tires, it does just over 3k rpm at 70mph, which I know is normal and I have no complaints. I just was wondering about the rest. The trans does not shudder or jerk. It engages very firmly.
Post Fiend
Joined: Jan 2005
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Not an expert by any means but may be able to give you some pointers.
The torque converter on a C6 does not have a lockup clutch so never locks.
The shift points are largely controlled by engine manifold vacuum fed to a vacuum modulator on the trans. Yours may be faulty. Pull the vacuum pipe off and look for any signs of trans fluid in the pipe. If you see any fluid replace the modulator.
There should be a kickdown cable or rod. If this is not connected you will not have kickdown and if the lever at the trans is not tied in the "off" position this could affect your shift points.
The torque converter on a C6 does not have a lockup clutch so never locks.
The shift points are largely controlled by engine manifold vacuum fed to a vacuum modulator on the trans. Yours may be faulty. Pull the vacuum pipe off and look for any signs of trans fluid in the pipe. If you see any fluid replace the modulator.
There should be a kickdown cable or rod. If this is not connected you will not have kickdown and if the lever at the trans is not tied in the "off" position this could affect your shift points.
Post Fiend
Joined: Jul 2006
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Shift points can be adjusted by turning the set screw inside of the modulator. This is provided that all is functioning properly, and you have no vacuum leaks.
Your engine rpm at highway speed is way off. With 3.55 gears and a 33 inch tire, you should be just slightly more than 2400 rpm.
Could you have a different ratio or could the converter be slipping more than you think?
Your engine rpm at highway speed is way off. With 3.55 gears and a 33 inch tire, you should be just slightly more than 2400 rpm.
Could you have a different ratio or could the converter be slipping more than you think?
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Tuned
Joined: May 2005
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From: MI
I forgot these aren't lock-up converters. Okay, I meant to say it locks in gear solid in 2nd and 3rd but 1st will let go when I let off the throttle.
I think it has 3.73 or 4.10 gears. After driving it more. The P/O said it had 3.55, but it definitely doesn't as fast as it takes off, and what you've said.
I'll look at putting a cable back on it, and I will check the modulator. If its bad, I'll find another one. Which way would the set screw need to be turned to increase shift points?
I think it has 3.73 or 4.10 gears. After driving it more. The P/O said it had 3.55, but it definitely doesn't as fast as it takes off, and what you've said.
I'll look at putting a cable back on it, and I will check the modulator. If its bad, I'll find another one. Which way would the set screw need to be turned to increase shift points?
Post Fiend
Joined: Jan 2005
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Before you start with the screw make sure you have full manifold vacuum at the modulator. Pull the rubber pipe off the modulator at the trans and with engine running, put your finger over the end of the pipe. You should be able to feel good vacuum. Get that right first.
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Tuned
Joined: May 2005
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From: MI
Alright, so there is no vacuum line hooked up. The modulator has a tube on it that does a quick little loop and is open. So, no kick-down cable or vacuum.
Do some shift kits delete the need for vacuum? The trans has a TCI pan and torque converter so I'm assuming it has a TCI shift kit. It currently shifts between gears way to quick to not have something done internally.
Oh, anyone know of where I can order a kick-down cable that isn't real expensive that'll last?
Do some shift kits delete the need for vacuum? The trans has a TCI pan and torque converter so I'm assuming it has a TCI shift kit. It currently shifts between gears way to quick to not have something done internally.
Oh, anyone know of where I can order a kick-down cable that isn't real expensive that'll last?
Post Fiend
Joined: Jan 2005
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You need the vacuum hooked up. There is normally a small bore steel pipe runs up the side of the trans and then up the back of the engine, Then at the trans end a short length of rubber pipe connects it to the vacuum modulator on the trans and a longer length of rubber pipe connects it to manifold vacuum at the engine end.
If you could keep it clear of exhaust and sharp edges you could possibly run a length of rubber pipe all the way (about the size of windshield washer pipe) and "T" it into a vacuum pipe at the manifold.
If you could keep it clear of exhaust and sharp edges you could possibly run a length of rubber pipe all the way (about the size of windshield washer pipe) and "T" it into a vacuum pipe at the manifold.
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Tuned
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From: MI
So could this be the reason I have such high shift points? No vacuum may make it shift like its at WOT, right? This mean having the vacuum hooked up will make it shift more like a normal trans again? I know I still have to put a kick-down on so it will downshift correctly, too.
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Post Fiend
Joined: Jan 2005
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Yes, with no vacuum the trans shift points will be very high. You need to get manifold vacuum to it to get the shift points to normal.
You really only need the kickdown hooked up if you want the trans to kickdown a gear at WOT for passing. Otherwise you could zip tie the kickdown lever at the trans to fully off, although it would be nice to have it working.
As for shift kits I would think that, unless you go for a full race kit where all the shifts are manual, you would still need a vacuum supply if you want automatic shifts.
You really only need the kickdown hooked up if you want the trans to kickdown a gear at WOT for passing. Otherwise you could zip tie the kickdown lever at the trans to fully off, although it would be nice to have it working.
As for shift kits I would think that, unless you go for a full race kit where all the shifts are manual, you would still need a vacuum supply if you want automatic shifts.
Thread Starter
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Tuned
Joined: May 2005
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From: MI
Alright, now it shifts to 3rd really quick under light throttle(normal driving). I want to figure out this kickdown lever. It is the other lever thats attached to the gear select lever, right?
And there was no fluid in the modulator so I'm assuming its alright.
Which(and where) is a good, inexpensive kickdown cable? I want to get this thing shifting right as soon as possible cause its my dd.
Edit: How hard is it to turn it? I cant seem to get it to budge in either direction.
And there was no fluid in the modulator so I'm assuming its alright.
Which(and where) is a good, inexpensive kickdown cable? I want to get this thing shifting right as soon as possible cause its my dd.
Edit: How hard is it to turn it? I cant seem to get it to budge in either direction.
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Tuned
Joined: May 2005
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From: MI
Alright, figured it out. Someone clocked the kick-down lever so it was in the off position and against the shift lever. They hooked the cable from the floor shifter to the kickdown lever. So, I guess that is an awesome way to do it, eh?
I'll be looking for a kick-down cable and guess I will have to re-adjust the shifter and hook it up to the right spot.
I'll be looking for a kick-down cable and guess I will have to re-adjust the shifter and hook it up to the right spot.
4wd Low
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Seems to me, I have it stuck in my memory from somewhere.....light throttle C6 should shift 1-2 @ 17mph and 2-3 @ 27mph. Seems I read it out of a Chilton's manual years ago. And my experience with coming out of kick down mode is about 55 mph. If I'm wrong, somebody please correct me. 
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