Engine roughness when stopped

Engine runs perfect while idling in neutral or park. Runs great while underway. The second I come to a full stop while in gear the RPM’s dip and it starts shuddering/shaking.

Any ideas? Doesn’t happen all the time. Can’t tell if it’s a miss or what’s going on, it sounds really odd. Pop it into Neutral and it instantly smooths out.

11 months ago I dropped the pan, checked the bearings, new seals, oil pump, timing chain, water pump, t-stat, hoses, oil lines, etc. (freakin pan is leaking now, of course)

About 3 weeks ago I had a transmission cooler line fail. I lost 2-quarts of fluid which I quickly replenished and it’s been holding ever since.. wondering if I could be experiencing a torque converter issue? Problem seems to develop after driving for a few minutes. It’s an early style 4L80E with a cooler in addition to the radiator cooler

Sounds like the converter is not coming out of lockup.

Try unplugging the lockup solenoid pin or tune it for no lockup and see if it goes away.

Granted mine is turned this way, my rpm will stay up as I decel giving me engine braking. Then when I cross the 1500 rpm threshold it unlocks and goes to idle.

Maybe related to the transmission fluid issue you had. The injection pump should hold idle speed no matter what. It has no electronics.

Skinny said:

Sounds like the converter is not coming out of lockup.

Try unplugging the lockup solenoid pin or tune it for no lockup and see if it goes away.

Granted mine is turned this way, my rpm will stay up as I decel giving me engine braking. Then when I cross the 1500 rpm threshold it unlocks and goes to idle.

Maybe related to the transmission fluid issue you had. The injection pump should hold idle speed no matter what. It has no electronics.

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exactly what I was thinking shortly after I made this post. That’s for the troubleshooting advice. I have very little hands on experience with automatic transmissions

Tailwheel said:

exactly what I was thinking shortly after I made this post. That’s for the troubleshooting advice. I have very little hands on experience with automatic transmissions

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No doubt

What do you have for a trans controller? Any way you can plug a laptop in and see when the TCC is being commanded on and off?

You may be able to drive down the road and toggle it manually. That would be a great way to see if it's responding correctly.

Realistically it's either the TCC solenoid or the converter itself. Sure it could be a TPS sensor but that would give you a bunch of shift issues too.

Skinny said:

No doubt

What do you have for a trans controller? Any way you can plug a laptop in and see when the TCC is being commanded on and off?

You may be able to drive down the road and toggle it manually. That would be a great way to see if it's responding correctly.

Realistically it's either the TCC solenoid or the converter itself. Sure it could be a TPS sensor but that would give you a bunch of shift issues too.

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The lines run into the factory cooler on the radiator and then down to a secondary cooler below the radiator. It’s not ideal but I don’t really tow, the M1008 is my daily driver.

Do you think running it dry caused the issue?

I also have never flown anything with a tailwheel

I don't have a tailwheel endorsement either. But I want one.

Back to the truck issue. When I first read your original post my thought process went to idle speed just a hair too low. Others had jumped in with torque converter thoughts and I didn't post anything. Reading through the thread today I still went to idle speed thoughts.

Does this only happen after the engine is warmed up and off fast idle?

So yesterday I went into the transmission controller and changed the TCC value from 44mph to 45mph. Now the converter locks at exactly 45mph, I can hear and feel it. The TC unlocks at around 35mph while at throttle idle during decel. I could not replicate the issue... Perhaps it was just a transmission controller bug? I will drive it again later today and see what happens. It fired right up and ran really smooth during the entire test, idle was perfect.

Temps ran between 167 and 177 after a full warmup and no weight in the truck. I'm curious how high they get when towing. I have no fault codes of any kind.

Regarding the tailwheel flying, I have access to an 85hp Piper Cub and my own Piper Pacer Bushplane, should anyone want a tailwheel endorsement. I do tailwheel training and backcountry/mountain instruction on the side.

Thanks for the replies.

Glad the issue went away.

Where to set the 4th gear lock up is a question I have been playing with for a while on my 4L80E in my 6.5 powered Suburban. When I first started driving the truck I set it to 44 because a lot of my daily commute is in 45, 50 and 55 speed zones. Need to get that extra .2 mpg and all. Plus, it keeps the transmission temps down in the summer time. That worked great for me in my town.

Pulling a trailer with a load and it was shifting to 4th and locking up too soon. I would just loose all acceleration unless I really got into the power or caused it to downshift. Driving without a trailer in hilly terrain caused the same issues. I have slowly raised my lock up speed over time to where it is now at 59 mph. That makes it feel like a 5th gear during moderate acceleration and still lets me be locked up with a trailer at my trailer pulling happy speed of 63 mph.

Barrman said:

Glad the issue went away.

Where to set the 4th gear lock up is a question I have been playing with for a while on my 4L80E in my 6.5 powered Suburban. When I first started driving the truck I set it to 44 because a lot of my daily commute is in 45, 50 and 55 speed zones. Need to get that extra .2 mpg and all. Plus, it keeps the transmission temps down in the summer time. That worked great for me in my town.

Pulling a trailer with a load and it was shifting to 4th and locking up too soon. I would just loose all acceleration unless I really got into the power or caused it to downshift. Driving without a trailer in hilly terrain caused the same issues. I have slowly raised my lock up speed over time to where it is now at 59 mph. That makes it feel like a 5th gear during moderate acceleration and still lets me be locked up with a trailer at my trailer pulling happy speed of 63 mph.

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Any idea what temp your transmission normally runs?

I set the TC to lock at 55 and there seems to be a more linear acceleration now; however, it did increase temps.

My cooler is hooked up different than yours if I understand what you wrote correctly. I have radiator cooler to a stand alone cooler and then back to the transmission.

100° outside running down the highway locked my transmission control module tells me the fluid is 166° to 168°. I have gotten as high as 192° pulling a trailer in 45 mph speed limit hilly stop and go traffic on a really hot day which is just a torture test on the transmission but it went right back down to 168° within a few miles of being locked up with steady throttle.

We don't really get cold here. But, last January I did 300 miles out in west Texas with outside temps around 25°. The transmission stayed at 144° cruising locked.

Tailwheel said:

Engine runs perfect while idling in neutral or park. Runs great while underway. The second I come to a full stop while in gear the RPM’s dip and it starts shuddering/shaking.

Any ideas? Doesn’t happen all the time. Can’t tell if it’s a miss or what’s going on, it sounds really odd. Pop it into Neutral and it instantly smooths out.

11 months ago I dropped the pan, checked the bearings, new seals, oil pump, timing chain, water pump, t-stat, hoses, oil lines, etc. (freakin pan is leaking now, of course)

About 3 weeks ago I had a transmission cooler line fail. I lost 2-quarts of fluid which I quickly replenished and it’s been holding ever since.. wondering if I could be experiencing a torque converter issue? Problem seems to develop after driving for a few minutes. It’s an early style 4L80E with a cooler in addition to the radiator cooler

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.
Does the shaking and quivering happen only when your foot is on the brake peddle?
Maybe a crack in the rubber diaphragm in the brake booster?

Quick way to verify is to put the truck against a tree and see if it idles smoothly - without the foot brake engaged.

Barrman said:

My cooler is hooked up different than yours if I understand what you wrote correctly. I have radiator cooler to a stand alone cooler and then back to the transmission.

100° outside running down the highway locked my transmission control module tells me the fluid is 166° to 168°. I have gotten as high as 192° pulling a trailer in 45 mph speed limit hilly stop and go traffic on a really hot day which is just a torture test on the transmission but it went right back down to 168° within a few miles of being locked up with steady throttle.

We don't really get cold here. But, last January I did 300 miles out in west Texas with outside temps around 25°. The transmission stayed at 144° cruising locked.

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Thanks, that's about what I'm seeing but mine does tend to creep upward until lockup. I'll going play around with it today. Went to install a new #2 alternator this morning only to realize it was missing a post.... not sure how I didn't catch that before.. I'll do some testing later once its back together.

Mullaney said:

.
Does the shaking and quivering happen only when your foot is on the brake peddle?
Maybe a crack in the rubber diaphragm in the brake booster?

Quick way to verify is to put the truck against a tree and see if it idles smoothly - without the foot brake engaged.

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Yes but not all the time. If it does it again I will hit the parking brake and take my foot off the pedal to check. Here's my brake booster situation:

The hydraboost is a new rebuilt unit. I went through several before I got a good one. I disassembled it and sent it out to have it ported and flowed by BustedKnuckleOffroad, since I'm running all custom power steering and need -8AN and -6AN lines. I've had to pull the unit twice to replace the figure-8 seal, and it still leaks ever so slightly. I've got to top the reservoir every 6-months or so. I assume the housing isn't perfectly flat and I think I'm resigned to just topping fluid occasionally vs. risking the housing trying to machine it. Its been functioning, albeit with a slight leak, for a little over a year.

I'm running a PSC P-Pump with a -10AN feed line, and -8AN output line with a 4gpm restrictor. The hydraboost has a -8AN input and output that runs to a new gearbox. The gearbox to hydraboost return line is -6AN and the return line to the reservoir is -8AN. The reservoir is custom and internal filtered to 35-micron. To facilitate free flow from the reservoir to the pump I was able to modify the drivers side alternator bracket on a mill to allow a nearly direct path for the -10AN line to the pump. The system works great and I get full steering and braking at the same time, unlike with the stock GM setup.

I have the largest aux cooler ever made with three fans on it. Mounted to the side in front of the saddle tank. I have an M1031 so the box doesn't obstruct it.

My setup runs a thermostat to regulate temps and the factory cooler is no longer connected, complete stand alone system.

It runs dead nuts at 194 degrees which is what the controller is seeing in the pan. I may be able to get it to 210 if I'm flogging it but never above that which is pretty good. You don't want fluid to cold but I think anything above 230 is probably getting too warm. I also run Dex 6 (or is it 5, I forget) which is full syn.

I have the stock gutless wonder so too low of a pickup speed and she is dead. It definitely likes to be in vortex fluid flow

So I think mine is like 45mph. I really like the tuning. I keep mine programmed for pretty quick downshifts and better performance since I only have 160 horsepower to play with. So far I really like it. Tip in slightly and it immediately bangs a gear and goes. Sure it's not going to get the best economy but it keeps me sane.

I wanted to stab myself in the eye with a sharp object with that junk TH400. Oh you are above 35 mph...how bout some third gear only....

Skinny said:

I have the largest aux cooler ever made with three fans on it. Mounted to the side in front of the saddle tank. I have an M1031 so the box doesn't obstruct it.

My setup runs a thermostat to regulate temps and the factory cooler is no longer connected, complete stand alone system.

It runs dead nuts at 194 degrees which is what the controller is seeing in the pan. I may be able to get it to 210 if I'm flogging it but never above that which is pretty good. You don't want fluid to cold but I think anything above 230 is probably getting too warm. I also run Dex 6 (or is it 5, I forget) which is full syn.

I have the stock gutless wonder so too low of a pickup speed and she is dead. It definitely likes to be in vortex fluid flow

So I think mine is like 45mph. I really like the tuning. I keep mine programmed for pretty quick downshifts and better performance since I only have 160 horsepower to play with. So far I really like it. Tip in slightly and it immediately bangs a gear and goes. Sure it's not going to get the best economy but it keeps me sane.

I wanted to stab myself in the eye with a sharp object with that junk TH400. Oh you are above 35 mph...how bout some third gear only....

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I’m enjoying the 4L80E with 37’s. 55-70mph is comfortable all day. The more I think about it, and the more I zero in on what I want this truck to be, the more I want to swap in an early NV4500.

I used to be all about modernizing but now I just hate computer controlled stuff.

I’m contemplating stuffing a couple Derale 1000 series stacked coolers in front of the radiator and running a Griffin rad with shroud and electric fans. It’s a hard decision because I just replaced everything else in the cooling system with custom parts and it wasn’t cheap.

I thought about the NV4500 for the exact reasons too but couldn't pull the trigger. Everything I read about that trans is the gear ratio gaps do not work well with a low rpm low power engine.

I'm 100% satisfied with the 4L80 so I'm going to keep it.

Skinny said:

I thought about the NV4500 for the exact reasons too but couldn't pull the trigger. Everything I read about that trans is the gear ratio gaps do not work well with a low rpm low power engine.

I'm 100% satisfied with the 4L80 so I'm going to keep it.

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The 4L80E is one tough transmission. Maybe I should leave it alone.

And just for the sake of information gathering, since adjusting the TCC lock-up speed up 1mph I have not been able to replicate the issue. I’ve driven several hours both city and some quiet back-country highway. Everything is working normal.

With outside ambient temps of 47 - 56 degrees, 24-bolt HMMV wheels and tires, and a few hundred pounds in the bed, I could not get the transmission temp over 180. Even running wide open up some rolling hills.

The trans cooler output line runs to the radiator, from the radiator it goes to cheap NAPA cooler mounted horizontally below the radiator, and then back to the transmission. Nothing special.

I have a NV4500 behind the 6.2 non turbo engine in my M715. Same basic weight as a M1009 but totally different gears. 5.87 compared to the 3.08. I have to agree that the 4L80E is much better for driving with a low power engine. Especially with any kind of load or trailer.

Plus, the NV4500 is a very delicate unit. Fiber washers that require special $60 a gallon oil the last time I purchased some before the current hyper inflation rates. The input shaft bearing does not like to live long either.

I am a manual transmissions rule kind of person. Yet, if I were to build either truck again. I would probably go 4L80E. The total cost involved is about the same and the utility of the 4L80E is more user friendly in every situation I operate my vehicles.

Barrman said:

I have a NV4500 behind the 6.2 non turbo engine in my M715. Same basic weight as a M1009 but totally different gears. 5.87 compared to the 3.08. I have to agree that the 4L80E is much better for driving with a low power engine. Especially with any kind of load or trailer.

Plus, the NV4500 is a very delicate unit. Fiber washers that require special $60 a gallon oil the last time I purchased some before the current hyper inflation rates. The input shaft bearing does not like to live long either.

I am a manual transmissions rule kind of person. Yet, if I were to build either truck again. I would probably go 4L80E. The total cost involved is about the same and the utility of the 4L80E is more user friendly in every situation I operate my vehicles.

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Thanks for the input. I was just searching around an an NV4500 came up locally. 2WD unit, unknown condition, but its the 93 GM with the tall first gear. The case is completely covered in dirt/rust..... Asking price..... $1,500 firm.

I'm sure that will sell just as quickly as the $35,000 square bodies folks keep trying to sell.