Speedo bouncing off speed limiter

jeeplj · 02-09-2010, 02:58 PM

Having an issue with my Dad's 06 TJ. At about 70 mph, the speedometer needle starts bouncing around. It sweeps from as low as 60 mph up to over 90 mph. When it hits 93, the engine is killed by design but then comes back after the needle dips again. So the result is, at 70 MPH, the Jeep is jerking down the road with the engine cutting off and on.

I advised him to replace the speed sensor and at the same time, inspect the gear for any unusual wear. I wasn't there when he installed it but he says the gear looked fine. He also says that he installed the sensor with the same clock orientation that it came out in. The problem persists.

Yesterday without consulting me, he took it to the dealership. They pulled the tail shaft housing off the t-case, said everything looked fine there so now they have to split the t-case!!! Fortunately, I was in the room when that call came in and told my dad to tell them to put it back together and not touch it anymore.

I'm going to dig into it myself this weekend but has anyone had any similar issues with the speedometer? I suspect it's not the guage itself because of the way the limiter is killing the engine. Seems more like it be the communication between the speed sensor and the computer. No code is being stored.

Info about the vehicle:
2006 TJ Sport
4.0, automatic
Completely stock other than cold air intake and a flowmaster muffler installed by previous owner.
It only has 31's so I doubt that the speedo gear was ever changed.

Thanks in advance!

Wes

**biffgnar** · 02-09-2010, 03:00 PM

Quote:

Originally Posted by jeeplj

It only has 31's so I doubt that the speedo gear was ever changed.

Thanks in advance!

Wes

I'll let others comment on the potential issue, but can tell you with respect to this point that the speedo without adjustment on my 06 Sport w/ 4.0 auto was more accurate on 31s than it was on stock tires.

**Jerry Bransford** · 02-09-2010, 03:02 PM

I would pull the speedometer gear out of its housing on the side of the transfer case and verify its condition. They are made from nylon plastic so if the previous owner screwed with it and it wasn't reinstalled properly, it could have been damaged.

jeeplj · 02-09-2010, 03:43 PM

Thanks Jerry. That's exactly my plan. Plus I feel the need to check the work of the dealership mechanics that pulled the tail shaft housing off. How much you want to bet that they didn't even clock the sensor correctly when they put it back in? This is the same dealership that argued with me over the location of the speed sensor in the first place... they insisted that it was on the ABS ring and when I told them that this vehicle doesn't have ABS, they argued with me.

Niceface · 02-11-2010, 05:42 PM

My jeep just starting doin this exact thing today home from work. It's been raining all day long, and I hit a big puddle , so Im' wondering if that is the culprit.

It's drying out in the garage now, and I'll see what it does in the morning. I replaced the speedo gear back in October when I did my axle/gear swap. It's worked perfectly since then, but then just started acting up today.

silly jeeps, just like women..high maintance, and are never 100% happy!

jeeplj · 02-12-2010, 12:25 AM

I ordered the gear today and will pick it up in morning. I can't believe they get $76 for those now! I swore I paid half that when I changed mine a few years ago. Hopefully Dad will be screaming down the road at 70 mph tomorrow.

Niceface · 02-12-2010, 08:15 AM

Quote:

Originally Posted by jeeplj

I ordered the gear today and will pick it up in morning. I can't believe they get $76 for those now! I swore I paid half that when I changed mine a few years ago. Hopefully Dad will be screaming down the road at 70 mph tomorrow.

You should have asked aroudn on the forums. What tooth did you order? A couple of us keep a few spares.

Tuffjeeper · 02-12-2010, 09:29 AM

I got my 39 tooth gear from Quadratec yesterday for $40! If you can, cancel the order lol.

jeeplj · 02-15-2010, 11:58 PM

Put the new gear in (33 tooth - 31's with 3.73s). No problems for a couple days but today it started again, only this time at a lower speed. Now I have to start thinking electrical I guess. The only other part I have not seen with my own eyes is the gear on the output shaft. I suppose it could be the problem too. I hate wasting time and money on stupid things like this, even more so when it's not my Jeep! Gotta take care of your dad though, right?

Regarding the price, didn't think about Quadratec. I did call 4 Wheel Parts and they were the same price as Jeep. The parts guy at the dealership said that ever since they went "teats up" the price of parts has skyrocketed.