# Help Shaking over 45mph low RPM



## icebeast00 (Jan 20, 2012)

96 nissan d21 hardbody automatic 103k. Have replaced transmission fluid, spark plugs and wires (and non foulers), fresh oil, new K&N air filter.

I have a shake in my truck that I can't pin down. It shakes and stutters/sputters when i get 45-55 (haven't tried it over 55), but only when i am decelerating. If i let completely off of the gas nothing. If I accelerate nothing. But if I let off the gas pedal and barely push (like if you were trying to keep a constant speed on flat ground) it shakes like hell. This is when the tach is at 2000 to 2500 rpm. If I turn OD off it goes away but then I can feel it when the car slows down to bring the tach back down to around 2000 but it is not as bad.

I have been driving around with OD off and that helps a little.

Any thoughts or help would be greatly appreciated!


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## dvdswanson (Nov 6, 2005)

What did the old tranny fluid look and smell like?


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## jdg (Aug 27, 2009)

Check out the U-joints on the drive-shaft.
Accelerating, decelerating, pressure is on the u-joint bearings on one side or the other.
When, as you described, you have your foot on the gas just enough to barely keep moving, if not slowing down just a little bit, there's not a lot of pressure on the u-joints one way or the other.
As far as why the shaking is less with OD off, I dunno... Could be that the engine is revving up higher and it's a bit harder to keep the u-joints in that perfect spot where they cause the shake.
But you also said it shakes/stutters,etc. so you're eluding to an engine issue.
When was the last time you gave it a good tuneup? Maybe put a can of HEET in the gas tank, etc.etc.etc.


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## icebeast00 (Jan 20, 2012)

dvdswanson-The old tranny fluid was darkish in color but it didn't have any strong smell to it and there didn't appear to be any oil or coolant that leaked into it.

jdg-I'm not quite sure how to go about checking out the U joints so I will try to look that up and get back to you on that one. With the U joints, is that going to be a case of tightening up some bolts of will the joint need to be replaced?


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## icebeast00 (Jan 20, 2012)

Oh and 2 gas fill ups ago I put some seafoam in there and like i said has fresh oil, plugs, wires air filter, tranny fluid. so I don't think its a tuneup issue.


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## jdg (Aug 27, 2009)

U-joints - Get under there, grab the driveshaft and give it a good shake and/or twist at either end. ANY slop between the driveshaft and the yokes at either end (transmission or rear diff) means you've got a bad u-joint. You might have to put the transmission in neutral to help detect the slop, and might even have to get one of the back wheels off the ground to "unbind" everything.


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## TheRepairMan (Jun 30, 2009)

Following the replies here I agree all these things need to be ruled out, but the way I read this it could almost be taken as an engine problem also. It's real hard to say without actually seeing the truck run, but I've had vehicles come in that acted this way that had EGR problems, dirty throttle bodies, timing was off, idle motor problems, etc. Or a combination of things.

My little Honda Civic does this acting up at part throttle sometimes. Mostly when the engine isn't completely warm, and when it happens I have to either go up or down a gear to get it to stop, otherwise it would shake the radio out of the dash. I'm thinking it may break something eventually. Under most conditions, with a fully warm engine, the car is so smooth you can't tell it's running.

Now, my D21 still shakes ALL the time I'm moving, but nearly goes away completely once the tires are warmed up good. I can clearly tell it's a tire related vibration on my truck versus an engine fueling/ignition problem on my car, even though they seem similar vibration at times. So, I'm just suggesting a careful inspection of all systems for the OP to isolate his truck's concerns.

Another thing to note, is that if you jack the truck up to check the drive shaft and u-joints you have to lift it by the rear axle rather than by the frame or you drastically change the drive line angle and may mask the play in the u-joints. That is, unless they are just completely shot.

-Roger


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## zanegrey (Dec 5, 2005)

CHECK CARRIER BEARING AS WELL...ALSO CONSIDER CHECK UR TIRES FOR BALANCE...


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## icebeast00 (Jan 20, 2012)

ok guys, sorry for the delay. weather here was crappy and I don't have a garage to work in. 

I got the truck up jacked by the rear axle put the truck in neutral. The forward-most U joint had the slightest play in it, we are talking 1cm or so. The other joints all down the axle were rock solid. and the rubber grommet (carrier bearing??)for lack of a better term that the axle goes through is still cushiony (if thats a word) and is not cracked or dry rotted. 

I double checked fluid levels (tranny and oil) they were ok. Everything on the air filter was good. Double checked tire pressure, same on all 4 tires.

Now since the bad weather I have to concrete filled tires in the bed of my truck for traction (2wd). I wouldn't think that would have any effect on the u joint play as long as i jack it up by the axle...correct?

So would that little play be the culprit or does this sound like possibly EGR issues like repairman suggested?

Thanks for the help!


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## TheRepairMan (Jun 30, 2009)

icebeast00 said:


> ok guys, sorry for the delay. weather here was crappy and I don't have a garage to work in.
> 
> I got the truck up jacked by the rear axle put the truck in neutral. The forward-most U joint had the slightest play in it, we are talking 1cm or so. The other joints all down the axle were rock solid. and the rubber grommet (carrier bearing??)for lack of a better term that the axle goes through is still cushiony (if thats a word) and is not cracked or dry rotted.
> 
> ...


I hope you meant 1mm instead of 1cm of play, as a centimeter is 10mm, and that would be an awful lot of play anywhere in a drive line.

So, we are still trying to determine if it's an engine misfire at part throttle, or drivetrain vibration. Now, in reading your first post again I'm thinking more down the line of a problem with the Torque Converter's Lock Up Clutch. Especially because of the vibration going away when you let off the throttle or when you accelerate through the vibration zone.

A change of trans fluid, and adding a product called "Shudder Fixx" might help, or at least prove to be a good test tool. That much doesn't cost a lot to try. http://www.lubegard.com/~/C-230/Dr.+Tranny+Instant+Shudder+Fixx

Oh, and no... A small bit of added weight in the bed isn't going to create a problem with the drive line normally, of course when there's something wrong with a vehicle any weight "may" exaggerate it.

Also, it's very easy to verify the EGR isn't or is part of the problem by just unhooking the vacuum hose going to it and plugging the hose for a test drive. A MIL will probably light for low EGR flow, but at this point that won't matter just for test purposes.

-R


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## icebeast00 (Jan 20, 2012)

Oh sorry yes, 1mm of play. It was not rock solid like the other U joints, but I seriously doubt that tiny bit of play (it was hardly noticeable) would be the culprit. 

And I actually just flushed the tranny fluid, put in a new filter and added Lucas Stop Slip about 300 miles ago. Not sure if the shudder fix and Lucas are essentially the same thing and just a different manufacturer.

Oh and the added weight does not seem to have exaggerated the problem.


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## jdg (Aug 27, 2009)

1mm play? As in 1mm when you try to rotate the two opposing parts against each other?
Whether or not that's the cause of your vibration or not, a u-joint should be SOLID, not just 'hardly noticeable play'. There should be no question at all if the u-joint is tight or not. Maybe there is actually a tolerance for that sort of 'play'. I don't know...never looked for one. In my mind, solid u-joint = good, ANY play = bad.


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## TheRepairMan (Jun 30, 2009)

jdg said:


> 1mm play? As in 1mm when you try to rotate the two opposing parts against each other?
> Whether or not that's the cause of your vibration or not, a u-joint should be SOLID, not just 'hardly noticeable play'. There should be no question at all if the u-joint is tight or not. Maybe there is actually a tolerance for that sort of 'play'. I don't know...never looked for one. In my mind, solid u-joint = good, ANY play = bad.


Actually, true, no play is correct, but a u-joint can become dry and actually bind up and cause a hell of a vibration. About the only way to detect that, unless it's noisy, is to drop the shaft and check it by hand. It should flex very smoothly with no slop or stiffness.

-R


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## jdg (Aug 27, 2009)

TheRepairMan said:


> but a u-joint can become dry and actually bind up and cause a hell of a vibration. About the only way to detect that, unless it's noisy, is to drop the shaft and check it by hand. It should flex very smoothly with no slop or stiffness.


Aye...good point. Rusted solid u-joints suck...


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## icebeast00 (Jan 20, 2012)

Yeah I'm not saying that the front U joint is 100% good to go, it could probably use replacing. But at the same time I'm thinking that it might not be the culprit. So I do intend to change that u joint at some point. But first I wanna isolate this problem and get that figured out so I am not just going trial by error replacing parts.


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## icebeast00 (Jan 20, 2012)

I just got back from lunch and with the two weighted tired in the back of my bed it shook a LOT less. I could still fell the jumping/shaking but much less than it had been. Not sure if the added weight just muffled it. 

I was also thinking that this may signal that the issue is coming from the back end? U joint too tight at the rear axle?

A second thought, if it was engine related wouldn't the strain of the added weight exacerbate the problem?


Was considering taking out the EGR and spraying some brake cleaner on it but not sure how much that would help.


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## jdg (Aug 27, 2009)

Loaded down the bed and it shook less...
One thing that comes to mind is you messed up the "pinion angles".
Check the angle between the driveshaft and the transmission, and the driveshaft and the rear axle. They should be the same, within a couple of degrees.


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## SPEEDO (Jun 9, 2003)

might check to see if you threw a weight off of the driveshaft and check for bad motor/trans mounts...


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## icebeast00 (Jan 20, 2012)

Ok I will check those angles. 

I find it hard to believe that bad motor or tranny mounts would cause the described shaking since it is not constant, only at a very specific time.

In the meantime, if the angles are messed up or I threw a weight am I hurting the truck by driving it like this? Because it actually seems to drive better...


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## jdg (Aug 27, 2009)

Sure it would...
Decelerating, the load, the "twist", is on the "other side" of the mounts. Maybe that side of one of the mounts is in bad shape causing the engine/transmission to kinda stand up on one side or the other changing pinion angles.
But if the engine isn't in good tune in the first place and has other issues...well, all bets are off, and we can speculate all day until you get first things done first.


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## icebeast00 (Jan 20, 2012)

Okay so took the truck to the shop. Check engine light wasn't on, but they said they pulled an error code for misfire on cylinder 4. I had put non-foulers in, they pulled them out and said that was the cause of the misfire. They had no explanation for why it only misfired on cylinder 4 when I had non-foulers on all 4 spark plugs. The shake went away significantly, however it is still there. I ran it by Advance Auto Parts and pulled teh error code p304 misfire cylinder 4 and p1130 swirl valve control solenoid valve. 

There seems to be all kinds of differing information on this part and whether it will cause the truck to run bad or not, and also whether it's easy to replace. 

Beyond the mild shaking I am also getting horrible gas mileage, less than 10 mpg...


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## w9bna (Oct 11, 2011)

could it be the torque converter lock-up not functioning properly? And unrelated, why are you using non foulers? I always had power loss with those.


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## icebeast00 (Jan 20, 2012)

not sure how to check the torque converter lock up....

I had put the non-foulers in because I thought I had an oil leak and was trying to avoid replacing the seal. But Mechanic said he did a compression test and everything came back fine, so as of now they are sitting on my work bench (money well spent lol)


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## jdg (Aug 27, 2009)

icebeast00 said:


> not sure how to check the torque converter lock up....


If you've got a tach...Warm up the engine. Drive down the highway, straight and level ground, about 50mph. Tap on the brakes just far enough to light the lights but not far enough to engage the brakes. The rpms should jump up say 200-300 rpm or so and may or may not come back down right away or might not come back down until you take your foot off the brake.
If you don't have a tach, just try listening really closely to the engine rpms.


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## icebeast00 (Jan 20, 2012)

So if the RPM's jump up like that and stay up the torque converter is good?


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## jdg (Aug 27, 2009)

icebeast00 said:


> So if the RPM's jump up like that and stay up the torque converter is good?


Yep, but I gotta throw out a disclaimer that I'm also assuming this transmission/torque converter system operates like pretty much every other system out there that I've messed with.
If you pay enough attention while accelerating, you should be able to count the upshifts and you'll get one extra, which will be the T/C locking up, unless it happens at the same time as an upshift (entirely possible but again, I don't know for sure).


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## icebeast00 (Jan 20, 2012)

Ok thanks JDG. I will give that a try on my lunch break and report back.


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## SPEEDO (Jun 9, 2003)

bad mpg's can be 02 sensors...


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## icebeast00 (Jan 20, 2012)

Yeah I have heard of that before, but the MPG decrease came one pretty suddenly in sync with this problem. So I'm assuming the two are related, but I could be wrong.... 
And short or trial by replacing I don't know any way to test an O2 sensor for that purpose. I know the OBDII isn't throwing any O2 error codes.


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## icebeast00 (Jan 20, 2012)

Ok checked out the torque converter like you suggested JDG. When lightly tapping the brake pedal the RPMs did jump a little and stayed up there. There was no abnormal shaking or noises during this test, so I am assuming the torque converter is functioning properly. 

Guess it's back to checking out that swirl valve... gonna try that Friday


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