Transmission question

[phmilo]

Just got back from a 5K mile road trip to the southern tip of Baja. Truck ran great, conquered everything in it's path.

Twice on the trip, the transmission did this odd thing were it felt like it was only partially engaged. Both times we had been driving and stopped, didn't shut down or shift out of drive. When we went to take off, there was little forward motion and a clicking/ratcheting sound. A couple of seconds on the brakes and a quick check around and we pulled away with no problem.

I'm sure this is an indication of something, but I'm not sure what.

Thoughts?

 

[HomersCanyonero]

What year is your GX470? Could this be the common drive shaft clunk? Mine does something similar when I come to a stop. When it's time to go, it feels like someone rear ended me with a tap.

Drive shaft issue can be solved temporarily by greasing the zerks and permanently by upgrading to a later year drive shaft. I think this only affected 2003 and some 2004.

 

[phmilo]

What year is your GX470? Could this be the common drive shaft clunk? Mine does something similar when I come to a stop. When it's time to go, it feels like someone rear ended me with a tap.

Drive shaft issue can be solved temporarily by greasing the zerks and permanently by upgrading to a later year drive shaft. I think this only affected 2003 and some 2004.

It's an '07, 90K miles. I did have the standard drive shaft clunk when we got it, but I've greased the u-joints and that has gone away. This is more serious - The engine revved up ~ 500-1KRPM and I heard the ratchet sound. I stopped and then it immediately engaged.

 

[HomersCanyonero]

Hmmm. Not sure what that could be. Have you changed the transmission fluid? It's due soon, but I doubt that's the issue.

 

[phmilo]

Yeah, this was only momentary, so I don't think it is the fluid. It really felt like it just wasn't quite in gear. But since I hadn't touched the gear lever, just stopped and started I can't figure out how that happened. And it only lasted a second, once I got off the gas, hit the brake and did a "WTF was that", everything worked normally.

It's only done it twice, but of course it did it while we were 2K miles from home in a place where support was limited and parts hard to come by. No harm, no foul I guess. The GX brought us home comfortably with no real incidents.

 

[HomersCanyonero]

Yeah, this was only momentary, so I don't think it is the fluid. It really felt like it just wasn't quite in gear. But since I hadn't touched the gear lever, just stopped and started I can't figure out how that happened. And it only lasted a second, once I got off the gas, hit the brake and did a "WTF was that", everything worked normally.

It's only done it twice, but of course it did it while we were 2K miles from home in a place where support was limited and parts hard to come by. No harm, no foul I guess. The GX brought us home comfortably with no real incidents.

Re: This is more serious - The engine revved up ~ 500-1KRPM and I heard the ratchet sound. I stopped and then it immediately engaged.

I guess you gonna have to keep an eye on it. It sounds like something is off. Maybe others can chime in.

 

[aztoytec]

Honestly it doesn’t sound good. I would drop the transmission pan and look for excessive metal inside.
After it makes the noise how does it go into gear? Is it smooth or kinda jerky and slow?

 

[aztoytec]

If you can record it while it’s happening.

 

[phmilo]

Honestly it doesn’t sound good. I would drop the transmission pan and look for excessive metal inside.
After it makes the noise how does it go into gear? Is it smooth or kinda jerky and slow?

Only did it twice. No warning and quick immaculate cure so not a chance to record it. The sequence was: we had been driving, stopped to look at something, but didn't shift out of drive (didn't touch the gear selector), sat idling for ~1-2 minutes, then when I went to take off the engine revved a little and heard the weird ratchet noise, but got almost no forward motion, hit the brakes, looked around then took off w/ no issues.

Afterward, everything operated perfectly, just like normal.

 

[binaryaudax]

I think I experienced something similar to what you're describing on a few occasions and it was always if I put the truck from reverse into drive too quickly (while still rolling back) or while stopped on an incline and then moving forward again... the truck would make a grinding/clicking noise and wouldn't move forward (would even roll back if on a hill like a manual without the clutch engaged). Coming to a complete stop and then pressing the accelerator would solve it.

It only happened to me about 3-4 times and I could never reproduce it when I tried. I flushed the transmission fluid around 165k miles and I don't recall having the issue again (~4k miles).

/shrug

 

[Rednexus]

I've also had this happen when trying to get out of a mudhole (shifting very quickly from D to R and back again).

As mentioned above, I would do a full flush of the transmission fluid. You should also do a pan drop at this time to check for any debris, to clean the pan, and to replace the strainer (which comes in a kit with the transmission pan gasket). This is the correct way to get out all of the old fluid and any sediment/debris that may contaminate the new fluid. It's not an overly difficult DIY job, but can also be done by a shop as well.

If everything looks fine and it doesn't happen again, I probably would not worry about it. Your transmission fluid is probably 15 years old - even with only 90K on it, it is an old fluid and probably needs replacement based on that alone.

 

[binaryaudax]

Your transmission fluid is probably 15 years old - even with only 90K on it, it is an old fluid and probably needs replacement based on that alone.

Agreed... my 2007 had ~165k at the time and the ATF was black.

 

[Rednexus]

Agreed... my 2007 had ~165k at the time and the ATF was black.

At 135K and 13 years, my 2007's fluid was the color of blackberry syrup, but not quite all the way black . Folks love to forget about transmission, differential, and transfer case fluid changes.

 

[phmilo]

Good points all, ATF swap is now on the todo post-it pile.

Editing to add: This truck is fantastic. 5K plus miles through hostile environments (west coast Seattle to Cabo and back and lots of exploring). The worst thing that happened was the gas jockeys in Oregon messing up my gas cap and causing a check engine light. Picked up some friends at the airport and gave them the 'limo' ride back. Just tough/dirty enough to not get too much attention, but super comfortable and capable. Never had to break out the recovery gear (admittedly I played it pretty safe due to our remoteness most places that were risky). These are fantastic rigs.