Allison 6sp: Built trans shit the bed?

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ClarkW

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Feb 11, 2009
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Truck is an 07 classic ccsb 4x4 195K miles, lift pump, efi live with idaho rob tuning, 450whp ish, 33" tires, no lift. I had my trans built back in 2010 (@100k) by Mike L. It's got a suncoast kit, and mikes converter, plus whatever tricks he does. Everything has worked great for the last 100k miles. I daily drive, tow often but usually under 10k, and I go through rear tires quickly.

Now in the last week or so i had a couple shifts that missed, revving up, then banging into gear while driving casually, it did it a couple more times, and then wouldn't shift out of 1st. Then the tires locked up, had to drive in reverse to get it to free up, and then limped in 1st a couple miles home.

CEL is on, codes p0700, p0757, and p2724. Fluid is at the bottom of the hot hashmark when warm, looks clean, and i change the spin on every oil change. Trans usually runs below 210, above 150 depending on temp and how i'm driving. Has hit 230 towing up fireroads last summer.

I read up a little bit on it and sounds like i may have chunks of clutch material lodged in the valve body causing some selenoids to stick.

Is it salvagable or time for another rebuild? Will i be able to save any money since it's already built, or is it the same as starting with a stock trans?

 
aklbz

aklbz

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I'm sure Mike will chime in and give you his thoughts


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Nickracer9

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May 23, 2012
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Check your transfer case. My truck had some similar things happen when a snap ring broke in there. The speed sensor in the t-case can get some jacked up signals from materials(snap ring) floating around in there. Causing some very nasty bangs(tranny tie up). Check the oil for metal shavings and debri. I really doubt it's Mike's tranny!
 
Bonestock

Bonestock

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Aug 9, 2010
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After lots of abuse and that many miles also built with clutch material from what was available back then there is a possibility your c3 clutches and steels took on all the heat they could withstand and gave it up. Thats alot of fun beating on a trans for 100k!
 
motoking_1990

motoking_1990

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May 9, 2011
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Sounds like it's time for a refresh. 100k is a lot of miles on any trans. That's money well spent in my book. If it were my trans that Mike built I would have him do the rebuild again. He knows he was the only one in it. He should be able to tell what failed and why. If Mike doesn't chime in pm him. That's where I would've started to begin with.

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ClarkW

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Feb 11, 2009
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I have replaced this filter twice since the original the build, but not recently.

It doesn't smell good.....









 
C

ClarkW

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Feb 11, 2009
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Is there any way to see it without pulling the starter? I'm not sure what color it is.
 
JoshH

JoshH

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ClarkW said:
Is there any way to see it without pulling the starter? I'm not sure what color it is.
Click to expand...

There is a small plate that snaps into the bellhousing right in front of the spin on filter.
 
Chevy1925

Chevy1925

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motoking_1990 said:
Is there a way to know a head of time the tc is going?

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Click to expand...


I really didn't have much warning other than some interesting high rpm, light throttle up shifts. It did kill some of my clutches though from plugging up the filter.
 
SmokeShow

SmokeShow

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Nov 30, 2006
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Mike, you mean the clutches in the convertor went bad or in the trans or both? Just wondering as my MA-built SCIII (original SC convertor took a dump & it not has a loud ass ATS 5 Star in it) is shifting like ass lately. IDK whether to be looking for a convertor or a trans rebuild. Trans is approaching 90-100k miles on it. Its been good & still holds my sub500 rwhp just fine. Its just the part-throttle shifting has gone to shit - harsh & hangs.
 
Mike L.

Mike L.

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SmokeShow said:
Mike, you mean the clutches in the convertor went bad or in the trans or both? Just wondering as my MA-built SCIII (original SC convertor took a dump & it not has a loud ass ATS 5 Star in it) is shifting like ass lately. IDK whether to be looking for a convertor or a trans rebuild. Trans is approaching 90-100k miles on it. Its been good & still holds my sub500 rwhp just fine. Its just the part-throttle shifting has gone to shit - harsh & hangs.
Click to expand...

When the converter clutch starts going out you might feel a shudder when applied. Tech 2 will tell you what's going on. Converter clutches can start going out and not tell you anything for a while. Changing the sump filter and cutting it open will tell you a lot.
Allison states the sump filter never needs changing. So why did they put a filter there instead of a straight pipe?
Looking at the above pictures tells me a story about what is happening. The filter paper above shows ribs that were sucked against the plastic supports. You should never see this unless the pump is sucking itself dry. how would you know unless you looked?
Stock Allisons without any power programmer can go quite a while without an internal filter. High performance builds behind a powerfull engine will shed clutch material and start restricting the sump filter which will inhibit pump suction. You may not notice an ever so slight change in the shift quality, but it is happening.
Allisons will not show much of anything in the pan upon inspection, but peeling the sump filter open will show you what is or is not going on. opening the spin on filter usually won't tell you shit as it is a low pressure filter ( 125 psi max ) and is only there to filter solenoids and valve body.
 
motoking_1990

motoking_1990

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May 9, 2011
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Mike L. said:
When the converter clutch starts going out you might feel a shudder when applied. Tech 2 will tell you what's going on. Converter clutches can start going out and not tell you anything for a while. Changing the sump filter and cutting it open will tell you a lot.
Allison states the sump filter never needs changing. So why did they put a filter there instead of a straight pipe?
Looking at the above pictures tells me a story about what is happening. The filter paper above shows ribs that were sucked against the plastic supports. You should never see this unless the pump is sucking itself dry. how would you know unless you looked?
Stock Allisons without any power programmer can go quite a while without an internal filter. High performance builds behind a powerfull engine will shed clutch material and start restricting the sump filter which will inhibit pump suction. You may not notice an ever so slight change in the shift quality, but it is happening.
Allisons will not show much of anything in the pan upon inspection, but peeling the sump filter open will show you what is or is not going on. opening the spin on filter usually won't tell you shit as it is a low pressure filter ( 125 psi max ) and is only there to filter solenoids and valve body.
Click to expand...
How does one go about knowing so much about transmissions? Lol I have built a few gm transmissions but never will I have the understanding that you have of these things. Thanks for the useful information. I have had some weird shift happening to my trans here lately. May have to open it up and have you tell me what you see in my filter.

Really sucks being on the wrong side of the nation to the best Allison trans builder.

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