Shaking in OD Under Load

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andfern97

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Your not supposed to tow under load in OD.
Ever miss a shift, and grab a higher gear? Shudder, shake, OMFG I'm dieing here. Could this be your problem?
It was an open / light trailer with a small motorcycle on it - probably less than ~1500 LBs loaded, which shouldn't really be an issue towing in OD. Even with this small load, the shaking was definitely more noticeable under throttle in OD than without the trailer. Not sure I follow missing a shift - it's a 4L60E auto trans.
 

stutaeng

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It was an open / light trailer with a small motorcycle on it - probably less than ~1500 LBs loaded, which shouldn't really be an issue towing in OD. Even with this small load, the shaking was definitely more noticeable under throttle in OD than without the trailer. Not sure I follow missing a shift - it's a 4L60E auto trans.
Yeah, for that load, that shouldn't be a problem.

So going back to that table I posted earlier...It looks like if you put it in Neutral while it's doing that vibration, NOTHING inside the transmission is applied, so try that. I think if you have a driveline issue (u-joint, driveshaft or similar) the issue will remain. If it doesn't, then transmission related most likely?
 
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andfern97

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Yeah, for that load, that shouldn't be a problem.

So going back to that table I posted earlier...It looks like if you put it in Neutral while it's doing that vibration, NOTHING inside the transmission is applied, so try that. I think if you have a driveline issue (u-joint, driveshaft or similar) the issue will remain. If it doesn't, then transmission related most likely?
Sounds good - thanks! I tend to think that it may stop since I have to be on the gas for the vibration to happen, unless I just shift to neutral while still applying throttle. I'll give it a shot on my drive home though - thanks!
 

shawnmichael

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Hi all - asking for some advice / opinions. I have a '98 1500 with the 5.7, 4x4 / 4L60E, and ~200K on the ODO.
Recently, it's been shaking under load in overdrive. It's worst if I'm going up a hill and give it some gas to maintain speed - it will shake unless I let off the gas or give it enough for it to downshift. I've tried stepping on the brake slightly while it's shaking (to test TC lockup) and the shaking does not stop. I towed a small trailer recently, and the shaking was exacerbated (happening with any amount of acceleration in OD).

Engine has ~60K miles on it and trans was replaced ~3 years ago with an unknown mileage unit, but has been solid since. Do you suspect a trans issue? Maybe u-joints? I put a tube of ShudderFix in with no change (generally not a fan of magic solutions, but figured why not try). No codes / lights on dash. Any ideas would be appreciated, thanks!
If you're at the point of violent shaking shudder fix won't work. If you can force a downshift to third, do that. If the problem goes away, and everything else stays the same (speed, etc) it's your torque converter. I've got two Jeeps doing it right now, just waiting for an opportune time to pull apart.
 

GMTMark

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The 1998 trucks have PWM (pulse width management). This is a feature that allows a controlled slip of the torque converter clutch while it is engaged. Yours being a replacement transmission you could have a converter mismatch. It’s a lot to explain here so short story is you could have a worn out torque converter clutch or possibly worn 4th gear clutches. Neither of which would give you a code most of the time. The 4L60e had a lot of changes during that period and if you’re not very well informed they can give problems if you swap out to different model years. If your torque converter was built for earlier models the clutch will prematurely wear out. All the above replies are good info and do start with the simplest first.

When I build a 4l60e I try to build the transmission to the need of the customer. They are good units that the factory never built to their real potential.
 

andfern97

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Thanks for the additional replies, guys. I will replace the ignition coil and check the fuel pressure this weekend, but I have a suspicion the issue will persist. I'll say I did replace both the fuel pump and the spider (installed MPFI unit) within the last year, but the filter may be one to check still.

Good to know on the torque converter - the shudder is not the point where I'd describe it as 'violent' yet, but when pulling a trailer it definitely made for an uncomfortable ride. It does fix the issue if I force the downshift. The truck has driven / towed fine after the replacement trans ~3 years ago, but it could be that the TC has just worn out like you mentioned.
 
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shawnmichael

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If it's not a violent shudder yet then shudder fix might work but it took me 3 tubes on one of the Jeeps to stop a mild shudder. Remember they don't fix a problem, just modify the fluid to mask the issue. I ended up having to replace the pan gasket and lost the fluid and upon refill the shudderfix won't work in any amount (at least not less than 5). Bottom line, another tube or two might work but if it doesn't I think you need a new TC. I'll shut up now.
 
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