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C6 transmission whining when hot and losing gears


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I think I'm going to drop the pan again shortly. Replace it with a 2WD pan with a drain plug and corresponding filter, more fresh fluid. The 4WD pan I have with its pick-up tube is picking up gritty fluid from the bottom due to the fluid turbulence. I don't need a 4WD pan to go to the grocery store and work ;)

About the downshift, I'm hopeful that with time it will work itself out. I've just been manually dropping to 1 and it has been working well. I feel like I'm driving a one-leg operated manual truck http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/laughing-25-x-25_orig.gif

I agree with the approach so far of cleansing the transmission. I think most people I've seen post online just commit transmissions to 'rebuild' when they hear slip without actually troubleshooting it. The troubleshooting process can cost some but at least I have the satisfaction of trying my best before letting someone tear into my truck and hoping they put it back together just right.

I found a good tip on how to adjust vacuum modulator in this book. The book says never take vacuum modulator adjustment for granted based on how it shifts.

I will definitely be checking line pressure at different vacuum levels

https://a.co/d/1VheMeK

Capture.thumb.png.06fa8bfc442e56023cc3cf59d4cff200.png

Capture1.thumb.png.8d88c8d84c4e88089c60ff7dc351f68b.png

 

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I found a good tip on how to adjust vacuum modulator in this book. The book says never take vacuum modulator adjustment for granted based on how it shifts.

I will definitely be checking line pressure at different vacuum levels

https://a.co/d/1VheMeK

I tested the fluid pressure, here is a video on it. This looks to be in spec with the current vacuum modulator...

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I tested the fluid pressure, here is a video on it. This looks to be in spec with the current vacuum modulator...

Installed the transmission pan with drain plug and Motorcraft FT52 filter (without that pick-up tube).

https://shop.broncograveyard.com/C-6-Chrome-Steel-Transmission-Pan/productinfo/21104/

The pan isn't as shallow as the stock pan and actually needed the same amount of new fluid back as the old "deep" pan.

I must say everytime I dropped the pan, it looked cleaner each time. You guys were right I should have focused on getting new fluid in. I did add a small quantity of snake oil this time, hoping this is the final fluid change for a while.

The shifts are definitely firmer now, and I am getting better downshifts... but if I want anything better than this, I probably need a shift kit which is what I'm pretty sure Big Blue 2WD has.

If I get any sort of reasonable life out of this unit after seeing what all I got out of the pan, I gotta say the C6 transmissions are tough sunnagons!

 

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Installed the transmission pan with drain plug and Motorcraft FT52 filter (without that pick-up tube).

https://shop.broncograveyard.com/C-6-Chrome-Steel-Transmission-Pan/productinfo/21104/

The pan isn't as shallow as the stock pan and actually needed the same amount of new fluid back as the old "deep" pan.

I must say everytime I dropped the pan, it looked cleaner each time. You guys were right I should have focused on getting new fluid in. I did add a small quantity of snake oil this time, hoping this is the final fluid change for a while.

The shifts are definitely firmer now, and I am getting better downshifts... but if I want anything better than this, I probably need a shift kit which is what I'm pretty sure Big Blue 2WD has.

If I get any sort of reasonable life out of this unit after seeing what all I got out of the pan, I gotta say the C6 transmissions are tough sunnagons!

The C6 is really one tough son of a gun. Stands up to the 302 and 460 and everything in between. Not the most efficient, but strong. :nabble_smiley_good:

Glad it is working for you. :nabble_anim_claps:

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The C6 is really one tough son of a gun. Stands up to the 302 and 460 and everything in between. Not the most efficient, but strong. :nabble_smiley_good:

Glad it is working for you. :nabble_anim_claps:

Thanks to all for the help and advice so far!! :nabble_smiley_good:

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  • 3 months later...

Thanks to all for the help and advice so far!! :nabble_smiley_good:

Hi all, after about 1000 miles of driving I was happy, but I got really happy when all 4 BBLs of carb were unlocked. Sure enough, I think I have burned up the transmission in short order :nabble_head-rotfl-57x22_orig:

After about 25 miles of driving today, stop and go, the 1st gear is locked up. It won't move if I manually select 1st gear or if it is in D, but shifts 2-3 and 3-2 just fine. The fluid temp is fine, it was hovering around 195 or so. The supercooling radiator is doing its job... but an auxiliary cooler may have prolonged the life possibly.

I have honestly been waiting for this day so I can get the transmission rebuilt. The amount of mud I got out of the pan I have been shocked to see how tough the C6 has been.... will add an extra cooler as well (i'm sure the shop will recommend this). If I can get it to shift like Big Blue 2WD's I would be very happy.

Well, needless to say I will drive Big Blue 2WD to the truck show. Probably for the best it happened before I set out long distance.

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Hi all, after about 1000 miles of driving I was happy, but I got really happy when all 4 BBLs of carb were unlocked. Sure enough, I think I have burned up the transmission in short order :nabble_head-rotfl-57x22_orig:

After about 25 miles of driving today, stop and go, the 1st gear is locked up. It won't move if I manually select 1st gear or if it is in D, but shifts 2-3 and 3-2 just fine. The fluid temp is fine, it was hovering around 195 or so. The supercooling radiator is doing its job... but an auxiliary cooler may have prolonged the life possibly.

I have honestly been waiting for this day so I can get the transmission rebuilt. The amount of mud I got out of the pan I have been shocked to see how tough the C6 has been.... will add an extra cooler as well (i'm sure the shop will recommend this). If I can get it to shift like Big Blue 2WD's I would be very happy.

Well, needless to say I will drive Big Blue 2WD to the truck show. Probably for the best it happened before I set out long distance.

Yikes! Glad it quite now instead of part way up here in just over a week.

You might consider a torque converter with less slip. They are available and with the 460 I doubt you need much slippage. The reduced loss will help on MPG and reduce the temp of the fluid.

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Yikes! Glad it quite now instead of part way up here in just over a week.

You might consider a torque converter with less slip. They are available and with the 460 I doubt you need much slippage. The reduced loss will help on MPG and reduce the temp of the fluid.

Just to make sure I understand, you mean a converter with low stall speed, right ?

Sorry I'm bad on the terminology... I don't like automatic transmissions as I am a control freak and I feel I'm praying all the time driving one of those (obviously today :nabble_head-rotfl-57x22_orig:) and I wish they made new trucks with manuals.

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Just to make sure I understand, you mean a converter with low stall speed, right ?

Sorry I'm bad on the terminology... I don't like automatic transmissions as I am a control freak and I feel I'm praying all the time driving one of those (obviously today :nabble_head-rotfl-57x22_orig:) and I wish they made new trucks with manuals.

Yes. Monster has the C6 Torque Converter 1300-1650 Heavy Duty Low Stall torque converter. I'm not recommending Monster as some have had problems with them IIRC, but the idea is the same.

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Yes. Monster has the C6 Torque Converter 1300-1650 Heavy Duty Low Stall torque converter. I'm not recommending Monster as some have had problems with them IIRC, but the idea is the same.

OK I will ask for that style!

I wish I knew exactly what was in Big Blue 2WD. Even with the 3.08 gearing it is a beast. The torque converter is blue. That is all I know. I has been rebuilt, It most likely has a shift kit.

I'm planning to drive up Big Blue 2WD to the transmission shop and tell them "that's what I want".

The shop that will be doing the work is "Plano Automatic Transmission". They have been in business since 1966, the year C6 was introduced. The owner Jeff builds all the transmissions personally.... I think it will be in good hands.

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