Merc Mountaineer "jumping"

[toyman]

Hello all! Long time thankful reader of these posts. This site has helped me solve many problems in the past.

I've got a new problem now that I can't quite get a handle on though.

2000 Mercury Mountaineer V8 AWD 205,000 miles

Recently the truck started to act like it was almost jumping during city driving conditions @30-40 mph in third gear. The engine made no apparent change in RPM and the Transmission does not shift hard or clunk when changing gears to indicate a Transmission slip. Just two of three small "jumps" or shakes with a slight clunking noise underneath the vehicle when driving at moderate city speed when the truck is not shifting. Once on the highway or in top gear, the problem seems to go away.

I did add some of the Lucas Transmission "fix" about a month ago as a precaution but the problem is still there. Yesterday while looking around underneath the truck, I noticed a few drops of black fluid underneath the Transfer Case with the bottom of the case being wet as well. I have not had a chance to check the fluid level in the case yet to see if it is low.

Could this be an issue with the Transfer case, the Transmission or something entirely different?

 

[gavin]

turn Overdrive off when driving those speeds, and see if issue persists.

When I bought mine, I had a similar issue; with overdrive on, driving around 30-40, it will shudder. With overdrive OFF, the shudder would not occur.

I do not remember what the dealership did to resolve the issue; it was under warranty, and the paperwork I received and still have does not list what was done.

 

[RomeovilleIL]

turn Overdrive off when driving those speeds, and see if issue persists.

When I bought mine, I had a similar issue; with overdrive on, driving around 30-40, it will shudder. With overdrive OFF, the shudder would not occur.

I do not remember what the dealership did to resolve the issue; it was under warranty, and the paperwork I received and still have does not list what was done.

Ran into quirky shifting/shudder on our svt mustang right at 40-45 mph a few years back with no error codes. Cannot recall exactly how it tied into the trans, but dealership recommended changing plugs and wires. Fixed issue.

 

[toyman]

Thanks for the tips guys. I will try turning off the overdrive the next time I have it out driving.

The overdrive does seem to make sense as it almost seems like it is trying to kick in to overdrive at the lower speeds.

I am kind of wondering if a climate/driving pattern change could cause this issue to occur? We recently (about six months ago) were relocated by my wife's company to Lexington, Kentucky from Indianapolis, Indiana. While Indianapolis has a relatively flat landscape, Lexington is full of steep hills. In the subdivision we live in, we must drive up a steep hill for about 1/8 mile to get in to the neighborhood and then down another steep hill near the back of the neighborhood to get to our house. Perhaps the change in driving patterns has caused an issue to surface with the overdrive.

 

[swetrid]

It could be ignition problem or torque converter shudder.

 

[gavin]

Ran into quirky shifting/shudder on our svt mustang right at 40-45 mph a few years back with no error codes. Cannot recall exactly how it tied into the trans, but dealership recommended changing plugs and wires. Fixed issue.

guess I should have clarified... :
the issue was something with the trans; I want to say they reflashed the PCM to resolve the issue, but not 100% positive on that.

Thanks for the tips guys. I will try turning off the overdrive the next time I have it out driving.

The overdrive does seem to make sense as it almost seems like it is trying to kick in to overdrive at the lower speeds.

I am kind of wondering if a climate/driving pattern change could cause this issue to occur? We recently (about six months ago) were relocated by my wife's company to Lexington, Kentucky from Indianapolis, Indiana. While Indianapolis has a relatively flat landscape, Lexington is full of steep hills. In the subdivision we live in, we must drive up a steep hill for about 1/8 mile to get in to the neighborhood and then down another steep hill near the back of the neighborhood to get to our house. Perhaps the change in driving patterns has caused an issue to surface with the overdrive.

It's certainly possible that you never were going the right speed to have the issue. From what I remember, I pretty much had to be going a very specific speed for a little while before it would happen.

 

[toyman]

Tried turning off the OD yesterday while driving the vehicle a few times. It did seem to make the problem go away, but I'm not sure if I have driven it enough yet to tell.

I also managed to get it into my garage yesterday to have a better look around underneath the truck. After opening up the fill hole on the transfer case, I found out that is definitely not low on fluid (as proven by the oil that came gushing out!). But not only is there fluid on the bottom of the transfer case, there is also black fluid all around it on top and on the truck frame around the case. I also noticed black fluid (it did not smell like oil) on the bottom of the oil pan and between where the engine connects to the transmission. Especially (pardon my lack of knowledge of proper terms here) around the area directly behind the oil pan where there is an easily removable 1-1/2 inch rubber plug that allows you to see a large gear.

I also have a new symptom now too. When in reverse, the truck seems to almost shimmy or shake. It does not do this in forward gears.

Any further ideas?

 

[toyman]

And also, both the transmission and engine oil levels were perfectly fine. Did not seem low at all. The only driveway drips I have noticed were from underneath the transfer case.

 

[Gabe96Explorer]

You more than likely have a vac leak and under load it pulls and breaks the seal and this causes a miss.

 

[Turdle]

Try a new PCV valve and grommet. This is a "tricky" repair, but you should be able to do it. It should require just a basic tool set if any, and quite a bit of feeling around in a blind area. A bright, small flashlight will help.

 

[toyman]

Yeah, I know how tricky that one is. I have had a brand new PCV filter sitting in my toolbox, unopened, for years and have never had the time or patience to find it. Quite the odd spot that the designers put that in.

Perhaps I will try my luck at it again. Maybe I'll run over to Sears and see if they have one of those small extending pen-size mirrors in stock. Would be nice if it had a light on it too.

 

[Gus Gorilla]

A shimmy in reverse could be something alignment related. Unless of course we're still talking driveline and driveline shimmy. If that's the case then disregard.

Also, wasn't there a TSB years back about a shudder when the TQ Converter engaged which caused a bump or small surge type feeling. But it would repeat a few times per engagement. A PCM reflash changed the speed at which the TQ Converter engaged by a few and the pulsing strategy for engagement and it made the feeling go away. May not have applied to this model. Again, can't quite remember the TSB or which ones it covered.