80 Series Transmission Hesitation

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Mayh3msHand

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Hello eveyone, long time mud follower, 1st time poster. I purchased an 96 80 series about a year ago. I have done the full comprehensive baseline as posted from mud as well as complete front and rear end rebuilds and U joints. I'm currently working on the motor.

I haven't had problems from the trans but concerns. While driving, if I let off the gas and coast for a bit, such as a stop light or making a slow turn, if I dont fully stop and I give it gas to continue driving, I have a slight hesitation from the time the motor powers up to when the transmission picks up again and starts moving. The motor revs without going anywhere, then the trans will fall into gear again and allow me to continue. Not a large clunk or thump, just a hesitation and a slight jerk, as if its falling into gear again.

Is this normal? Or is there something else I should be looking at fixing?

When I purchased him, he had 235k on him, I replaced every filter and fluid on him using all Lucas products.

Thank you for the help ahead of time. I have been using these forums for a year now while rebuilding and they have been the absolute biggest help.
 
OffRoadScott

OffRoadScott

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I might be blowing smoke but I would check your kick down cable to see if it is within specs. If it is out of spec it would cause delays in down shifting and acceleration.
 
M

Mayh3msHand

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I might be blowing smoke but I would check your kick down cable to see if it is within specs. If it is out of spec it would cause delays in down shifting and acceleration.
Thanks Scott, I just read this forum and it seems about right with what's happening. I'll do this tomorrow and come back with an update.


80-series Throttle Adjustment - Land Cruiser Tech from IH8MUD.com
 
OffRoadScott

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Mayh3msHand

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I've spent the morning adjusting and playing with different positions on the kick down cable to no prevail. It seems the best position was the original it was in, as far as shift times. More than 1mm over adjustment caused a long delay in shifts, while 1mm under adjustment caused lagging in shifts.

The hesitation seems to only happen when the vehicle is under 15 Mph and only once it's in 1st gear. When around 10 Mph, when given throttle after coasting, the motor will rev and then the trans will take a moment to catch up to the motor, causing the jerk.

I made a video of it. But it wont let me upload it.

I do not think it's the throttle cable from the pedal. As it responds immediately when given gas. The trans itself is the hesitant one.
 
gummycarbs

gummycarbs

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If it's like what I experience on my '94 (A442F transmission vs your A343F), I think it's just the torque converter working normally. Every hydraulic transmission I've ever driven has that slight brake-to-throttle lag.
 
M

Mayh3msHand

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If it's like what I experience on my '94 (A442F transmission vs your A343F), I think it's just the torque converter working normally. Every hydraulic transmission I've ever driven has that slight brake-to-throttle lag.
When you say brake to throttle lag, are you saying that from the time you brake, to the time you give it throttle you will have a slight lag or hesitation from gas to driveline?

And on yours, do you have a slight jerk when the drivetrain does catch up?

Like I said, it hasn't given me problems, just something I have been noticing and wanted to know if I should be concerned.
 
gummycarbs

gummycarbs

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When you say brake to throttle lag, are you saying that from the time you brake, to the time you give it throttle you will have a slight lag or hesitation from gas to driveline?
I'm saying that you're braking to enter a parking lot, finish the turn, begin to apply throttle and you hear the revs rise a bit before the torque converter responds. It's not as smooth as the throttle transition in a stick-shift vehicle.
And on yours, do you have a slight jerk when the drivetrain does catch up?
Depends entirely on what you call a slight jerk.
 
SpenserAK

SpenserAK

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Your description sounds just like mine - happens when giving it gas again after a slow coast to a near-stop, such as when turning onto a different street in a slow zone, or if you are about to get a green light and don’t fully stop. Seems more prevalent if going uphill - turning onto my street goes from flat to a mild uphill, so I notice it there often. Doesn’t seem to happen from a full stop. Feels like it’s not quite locked up, and then grabs after a sec (wouldn’t call it a jerk), either on its own or by giving a little more gas to engage it. In between there is often a light shudder for that brief moment. Everything else feels perfect, cables are adjusted properly, fluid is good/full, and this truck has always been a DD with no abuse.

Transmissions are a system I’m still learning. When describing this to two different friends who certainly have more knowledge than I, they both suggested a band could need to be tightened. Any thoughts?

I get the auto lag thing described above, but this feels a hair outside normal operation, and not something I’ve felt on any other auto I’ve driven.
 
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Mayh3msHand

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Your description sounds just like mine - happens when giving it gas again after a slow coast to a near-stop, such as when turning onto a different street in a slow zone, or if you are about to get a green light and don’t fully stop. Seems more prevalent if going uphill - turning onto my street goes from flat to a mild uphill, so I notice it there often. Doesn’t seem to happen from a full stop. Feels like it’s not quite locked up, and then grabs after a sec (wouldn’t call it a jerk), either on its own or by giving a little more gas to engage it. In between there is often a light shudder for that brief moment. Everything else feels perfect, cables are adjusted properly, fluid is good/full, and this truck has always been a DD with no abuse.

Transmissions are a system I’m still learning. When describing this to two different friends who certainly have more knowledge than I, they both suggested a band could need to be tightened. Any thoughts?

I get the auto lag thing described above, but this feels a hair outside normal operation, and not something I’ve felt on any other auto I’ve driven.
This is exactly what's happening. Nor have I felt on any other auto trans I have. Which is why I became concerned. Mine is a slight jerk when it does catch though, enough to move you inside the vehicle. It doesn't happen often, only when moving slowly after a coast, like you said. Stop light, turn etc
 
Toyo Boyo

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You say you did a full comprehensive base line, rig has 235k on it.
Adjusting the cables is giving you no resolution.
Did you do anything to the auto box during the baseline?
Drain & refill with new ATF or a complete flush & refill?
What did the old ATF look like? Was it still red or burned brown?
Did you drop the sump and clean / replace the mesh filter?
Have you double checked and made sure the ATF level is correct?
Any leaks on any of the ATF lines?

You have to post 10 times before you can upload pics (I think 🤔).
 
Wrencher93

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This is exactly what's happening. Nor have I felt on any other auto trans I have. Which is why I became concerned. Mine is a slight jerk when it does catch though, enough to move you inside the vehicle. It doesn't happen often, only when moving slowly after a coast, like you said. Stop light, turn etc
You may just be feeling the shift from 1st to 2nd gear. I apologize if I missed it but I didn't see what speeds you were experiencing this at. If it's in a parking lot at really low speed the shift into 2nd gear is known to be a little harsh with the A343F. Mine has a harder-than-average shift into 2nd. I usually feel it when I turn into my neighborhood as there's a steep hill so you go from almost stopped in the turn to acceleration up the hill. When that shift into 2nd gear occurs it sometimes feels a little jerky/not smooth.
 
Grandlooser

Grandlooser

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Mine does exact same thing at certain spots every time. I've checked it off as wear and don't bother pursuing it because I'm sick of minor grievances turning into thousands of dollars and days of time.
 
M

Mayh3msHand

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You say you did a full comprehensive base line, rig has 235k on it.
Adjusting the cables is giving you no resolution.
Did you do anything to the auto box during the baseline?
Drain & refill with new ATF or a complete flush & refill?
What did the old ATF look like? Was it still red or burned brown?
Did you drop the sump and clean / replace the mesh filter?
Have you double checked and made sure the ATF level is correct?
Any leaks on any of the ATF lines?

You have to post 10 times before you can upload pics (I think 🤔).
I didnt do anything with the auto box, I dont remember seeing that in the baseline forum, and I might have overlooked that.

I did a drain and refill. From what I read on here, the older trans might not hold up to the pressures of a complete flush and others had problems after. So just a simple drain with a pan drop and screen filter replacement.

The fluid that came out was bright red, looked like it just came out of the bottle and smelled it as well.

I'm not going to lie, I'm not sure what the sump is, and this might be something else I overlooked during the baseline.

I have, I check my fluids regularly.

I havent seen any ATF leaks, only oil leaks from the valve cover and the oil pump. Major.

I have replaced everything with OEM parts. With the exception of Lucas oils, fluids and grease.
 
M

Mayh3msHand

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You may just be feeling the shift from 1st to 2nd gear. I apologize if I missed it but I didn't see what speeds you were experiencing this at. If it's in a parking lot at really low speed the shift into 2nd gear is known to be a little harsh with the A343F. Mine has a harder-than-average shift into 2nd. I usually feel it when I turn into my neighborhood as there's a steep hill so you go from almost stopped in the turn to acceleration up the hill. When that shift into 2nd gear occurs it sometimes feels a little jerky/not smooth.
What you're describing is precisely what's happening. From 1st to 2nd at low speeds. Parking lot speeds.
 
M

Mayh3msHand

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Mine does exact same thing at certain spots every time. I've checked it off as wear and don't bother pursuing it because I'm sick of minor grievances turning into thousands of dollars and days of time.
It sounds like it isn't much of an issue then. My concerns were because I live and travel in my 80. I just returned from Mexico with it. And I worried that it might be a issue that would give me a major problem somewhere later where I dont want to break down. But, you and a few others are saying its been happening to you for awhile. So maybe my worries aren't necessary.
 
SpenserAK

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Sounds like your ATF is fine so I wouldn’t worry about it, but for future reference you can do a fluid exchange rather than the type of flush I assume you’re thinking of. Essentially pull new fluid in as old drains out with engine running, I believe via disconnecting the cooler lines? Detailed info available on mud, of course, should you ever do it. A few drain/fills over time is all good though - that’s all I’ve done for fresh cherry red.
 
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Wrencher93

Wrencher93

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Sounds like your ATF is fine so I wouldn’t worry about it, but for future reference you can do a fluid exchange rather than the type of flush I assume you’re thinking of. Essentially pull new fluid in as old drains out with engine running, I believe via disconnecting the cooler lines? Detailed info available on mud, of course, should you ever do it. A few drain/fills over time is all good though - that’s all I’ve done for fresh cherry red.
I did the "exchange" method you're describing. Or at least, a version of it. Unhook the trans cooler line that goes to the bottom of the radiator (the one taking fluid back to the trans). Hook up some clear 3/8" (I think) tubing and run it into a bucket. I had my bucket marked on the side so I could see how much fluid I was pumping out. Start the vehicle, let a gallon or so of fluid out, turn the truck off, top off the fluid via the dipstick tube. Repeat until you get bright, clean ATF coming through the clear tubing.
 

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