4L80E shudders/grabs when downshifting out of OD - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-14-2007, 09:54 AM
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4L80E shudders/grabs when downshifting out of OD

My 97 Chevy truck shifts and runs great. However the 4L80E shudders/grabs when downshifting out of OD. It feels worse when towing. If you floor it to throttle shift it, it's much better (maybe not perfect), but if you're light on throttle and it shifts itself, it really grabs. Scary sensation (noise and hesitation). I've had the valve body bored/rebuilt previous to this problem and all was well. Seems to have come into play after an engine swap and isn't going away. To me it feels like the torque convertor doesn't unlock quick enough before downshift. Any ideas before tranny shop?

Local GMC dealer said there's a factory reflash/upgrade for my truck. My VIN never showed a reflash when I checked it. He said no guaratee, but he'd start there. They are the only dealer nearby I trust. Is this worth a try?

Local mechanic says he can plug in and tinker with 4L80E "values" with his computer tool to see if he can adjust away the problem.

Or should I bite the bullet and get a "perfomance reflash" from SSDiesel, Heath or Kennedy? Would these have the updated values the dealer's talking about? If it doesn't cure my ills, will another dealer flash overwite the custom programming?

I'm getting a headache!!

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Old 06-14-2007, 11:08 AM
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It could also be an over-run clutch issue, they apply when you shift out of OD.
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Old 07-20-2007, 10:24 AM
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Time for rebuilt tranny?

Time for rebuilt tranny?
Or are there things worth trying (solenoids or other items to try)?
Thanks for reply
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Old 07-20-2007, 11:13 AM
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4l80e

The newer the vehicle, the greater the chance that the dealer can "flash" the computer to correct a trans concern. Because of the logic that exists with newer computers.

Your's is not new enough, in my opinion, that a reflash will help.

Your local mechanic will not be able to "adjust away" the problem either, with his scan tool.

Take it to a trans shop you trust, and please let us know what you find out.
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Old 07-30-2007, 07:39 AM
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Recomendations for 4L80E reman trans?

When asked about swapping in new solenoids (specifically the TCC solenoid which has fixed/masked problems identical to mine) the best local idependent trans shop said it has "marginal pressures" and not to spend hundreds trying to track done a problem on a worn tranny with 190k. Time for a rebuilt one is what I'm being told.

So...does anyone have recomendations of where to get a HD TOW (not race) 4L80E reman trans? Price is a concern, but I'm keeping the truck (new engine recently) so it's not the only deciding factor. I've seen anywhere from $1500 "Roadmaster" thru $2750 "GM" (including shipping core etc). Anybody to specifically stay away from? Anyone have someone to rave about? My mechanic likes Jasper, are they OK?

Thanks for your replies.
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Old 07-30-2007, 08:57 AM
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4l80e

Jasper makes a good product, however, since I own a transmission shop I subscribe to the theory that the transmission should be fixed, rather than replaced.

A couple points of interest. The warranty on the jasper unit is ostensibly very good, 3 years or 75,000 miles.

But if you have a warranty issue be advised that Jasper pays $54.00 dollars per hour to correct the concern. Most shops are $80.00 per hour or above.

This means that if the trans fails and has to be replaced, you will be responsible for the cost difference.

The transmission can be fixed for less money than if it is just replaced.

If you have it fixed and there is a warranty issue, the shop that did the repair is responsible for whatever costs are incurred during the repair. No more money should come out of your pocket.

If you travel with the vehicle, long trips, out of state, etc. The Jasper warranty is nationwide, which could come in handy.

If you purchase a transmission and have it shipped in and there is a problem, find out first how the particular company handles this situation, ie cost of shipping, warranty payments etc.
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Old 07-30-2007, 10:42 PM
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190k miles on this trans?

it is waaaay past it's service life expectancy
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Old 07-31-2007, 07:41 AM
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4l80e

Yes Crosley, I concur. The end of it's life cycle!
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