Weird noise, RMP drop to 0...then runs OK. (1 Viewer)

[chopperjamie]

Hello,
I searched the forum for this problem but I couldn't find a solution. It is a bit tricky to describe, so here goes.
1998 LC 225K miles, new to me in February. Runs like a champ. Well taken care of but rough enough around the edges to be comfortable.
A few weeks ago, I was driving to work and out of the blue, it made a PHZZZZZZT noise kind of like a firework that you light on the ground and it spins and takes off. (sorry, its the best I can come up with). The RPM's dropped to 0 but the lights stayed on. This lasted for 3 or 4 seconds then it came back up to RMP and all was fine for a few minutes. Then the exact same thing happened again.
I just happened to be driving by the exit to my house so I pulled off the freeway, got by other car, parked the LC and I went on vacation for a few weeks. Since then, I haven't even started it.

Does anyone have any ideas or thoughts as to what happened? Of course, I think worst case scenario....but I don't even know where to start troubleshooting this.

Thanks in advance!
Jamie

 

[chopperjamie]

OK. More info because I know everyone is waiting for me to update this thread...

I finally dug the LC out of the shop and started driving it again last night. I had the issue happen once this morning on the way to work and I can describe it better. I am 99% sure the noise is gear related and I don't think the RPM's fall to zero other than the reaction of me jerking my foot off the gas pedal!!! A few threads on here mention CV splines stripping, but I would think that is all or nothing. I bought this for the snow so I engage all of the 4wd bits including the rear locker around once a month. I kind of remember cycling the 4wd right before this happened the first time, so when I got to work (after it happened again this morning) I cycled the 4wd and drove it in low for a few seconds. I drove it around 20 miles at lunch and it ran just fine.
I wonder....could I possibly not have had the transfer case all the way in H and it popped out, then when I lifted my foot of the gas, it re-engaged? I think I have a torn CV boot so I am going to pull the front end apart this weekend and inspect the splines, but I wanted to get any opinions with the new information.
Thanks!
Jamie

 

[Spike555]

Most likely your transfer case was not fully engaged in high, it slipped into neutral and the gears were grinding, then because it was half in half out of gear it slipped back into gear and all was well again.
I've had that happen on my Land Rover, in it's transfer case there is a spring that holds it in gear, that spring gets weak and unless the gears were fully engaged it could slip out of gear when under load.
This only happened if I had been in lo range and had not made sure it was all the way back into high range, it too was full time 4x4.

 

[chopperjamie]

Thanks for the reply Spike. I was expecting it this morning so I was paying attention and it felt like an old VW Bug I had that would pop out of 3rd.
That what made me cycle the transfer case. I have my fingers crossed.
Thanks again for the reply and confirmation
my suspicions.

 

[Spike555]

You're welcome. If it happens again try to pay attention to what you were doing throttle wise etc and report back.
But I think you're good to go.

 

[chopperjamie]

Well, it did it again this morning. There is a traffic circle that feeds the on ramp to the freeway I take every morning. I enter the traffic circle and drive 3/4 around it to the exit so I am in an extended slow, tight left corner for a while. Then the on ramp makes a very slight right on an uphill.....that is when it happens. It makes a gear whine and completely loses drive train, then there is a thud and the it works normally again. It happened twice on that up hill on ramp this morning. After that, the 15 miles to the gym then work were fine. I think I am going to pull the outer flanges and look at the CV clips and splines. If anyone has any other ideas, please feel free to share.

 

[RootMeanSqr]

I think a key point here is that you say RPMs drop to zero, i.e. your engine is dying or being killed by something. If it were a slipping drive train, RPMs should not be dropping.

I had a similar problem on my 2000, and thought it was my transmission going. I finally determined (or so I believe) that it was the starter relay. I believe it was faulty and would engage on its own, causing the starter to engage, which would then cause the engine to bog/die. In my case, the engine would completely die, and then start up again on its own, without even turning the key.

It's possible that you relay energizes so briefly that the starter engages and then disengages before your engine completely dies. This would also likely explain the gear noise you hear. Seeing how yours is also intermittent, like mine, you may consider the starter relay as a possible cause.

 

[chopperjamie]

Thanks for the reply! I will check the starter relay, but now I am not sure if the rpms drop to zero or if I am just yanking my foot off the accelerator! When it happens, it feels very mechanical. Like something in the drivetrain forcefully disconnects. Now that it has happened a few times, it feels like something lets go more than an engine quitting.

 

[Spike555]

I would check your transmission fluid level, being in a long slow turn like that your trans fluid will move to one side, then you straighten and hit the throttle, you don't have enough fluid to make the transmission work, it slips, fluid returns and everything engages.
Make sense? Basically your transmission is running dry for a brief moment. Then when the fluid returns and the transmission catches it puts a heavy and sudden load on the engine, you already have your foot off the gas so the engine is returning to idle with little to no fuel being added, then sudden load, it takes a sec for the injectors to respond, RPM drop, then everything catches back up and you're good to go.
Does that make sense?
I could be talking out my ass, but that is where I would start with the new info you included.

You can also continue your round a bout and see if it acts up if you stay in there a long time, go back to it like at night when theres no one on the road, see if it acts up after one time around or five. Just stay in that long slow circle.

Let us know what you find.

 

[chopperjamie]

Spike, I read your reply last night before bed and it made a lot of sense. I drove the truck a few miles and just before I got to the roundabout I pulled over and checked the transmission fluid. It was right in the middle of hot and cold, bright red and smelled good so I don't think that is the issue. Good suggestion though.
I locked the center diff, went through the roundabout and up the on ramp with no problem. I hit the freeway and unlocked the diff. About two minutes later on the flat, the noise happened. I watched the tach and pressed the gas a bit. The RPM's increased even though the truck didn't speed up. When the RPM's dropped a bit, the noise dropped and with a soft clunk, the truck was back under power.
The noise is "less spliney" if that makes sense, like when I find the culprit, It will be obvious because it is grinding itself to death.
Friday AM I am going to pull the wheels and hubs off to look at the CV's. I will update then.
Thanks a lot for the ideas. It is a bit more comforting to know I am not alone in this deal!
Happy Thanksgiving!

 

[Spike555]

Man I was hoping for it being a pint low on trans fluid because that'd be cheap and easy.

 

[flintknapper]

Sounds like a possible Torque Converter issue. Might be a good idea to take it to a transmission shop and see what they say.

 

[chopperjamie]

Ok. So I took the right side apart Friday. When I popped the dustcap off, the "c" clip from the axle fell in my lap with a bunch of shavings. Turns out the axle nuts loosened and allowed the axle to walk back and forth in the cap. The outer threads on the axle were....gone.
I ran down to AutoZone and got a new axle, ran to Toyota and got new axle jam nuts, lock plate and "c" clip, slapped it together and all is right with the world. I put a few miles on it this weekend and all sorts of noises are gone.

I think I got really lucky.

Thanks for the input and help on this. I really appreciate the replies and suggestions!
Jamie