Technical "Limp or safety" mode up on the rack while trying to diagnose a shudder/vibration.

[Will2012Pop]

HI
I have a vibration/shudder that I'm trying to diagnose in my 2012 500 Pop. It only happens when pulling above 3k rpm in 3rd and 4th gear. Push in the clutch or let off the gas and its instantly gone. Seems smooth in 1st, 2nd, and 5th at any RPM and fine at highway speeds. Engine runs smooth to all rpms in neutral. It had a new clutch less than a year ago and ran fine till this shudder started last week. Since then I've replaced the motor mounts and CV joints and shafts, with no change or throwing any codes.

My next thought was to put the car on the rack with someone in it. Run it up to the gears and rpm range where the shudder occurs to see if I could find the problem from underneath. There seems to be a "safety" or "limp" mode that activates and clamps down on the brakes when you press on the accelerator in any of the gears while the wheels are off the ground,

If anyone has thoughts/suggestions on the shudder and/or knows how to disable the "safety/limp" mode please chime in. Any and all help is greatly appreciated. Thanks

 

[portland_bill]

Most of us on here are in the UK, and you get different engines in the US, so we're a bit vague on the specs.
If it has a dual-mass flywheel, was that changed with the clutch? If not, it is a likely cause. Other than that I'd be looking at engine mounts, especially the 'dogbone' mount under the engine. It stops the engine rocking as drive is taken up, or gears are changed.

With it in the air, only the driven wheels are rotating. The ABS and traction control systems monitor wheel speeds and will get upset if the fronts are spinning, and the rears are stationary. Disconnecting them all may allow it to run normally, although it will bleat at you to tell you those systems are inoperative. Otherwise, you might need to get two helpers, to spin the rear wheels at the same rate as the fronts. There's a challenge.

 

[Will2012Pop]

Thanks for the knowledge and quick reply!
I had a guy do the clutch for me. I want to say that he didn't replace the flywheel and I don't remember if he had it resurfaced or decided that it was ok as it was. Ill check with him to see what he did.

It shudders when pulling up a hill in 3rd at 3k rpm but when coming down a hill with the car pushing against the motor its smooth at that same gear rpm and speed. If the flywheel was warped/damaged wouldnt it have the same shudder? Just thinking out loud and trying to figure out a way to blame it on something other than the flywheel so I don't have to tear it all back down again.

Dogbone was my first thought too but already changed and doubled checked it. So I didn't get that lucky.

I had all 4 wheels up but I bet I had the hand/emergency brake on! Maybe it will be that simple to get around the traction control .... or I'm picturing in my head a system of straps spring and pulleys to get the back wheels turning along with the front... what could go wrong? They should have a picture of it all when I make the Darwin awards! lol

 

[portland_bill]

The handbrake switch will feed into the traction system, so that might release it.
I also had a picture of belts, and did hope others saw that too.

Might have a misfire. When the engine is not pulling, it won't care about a misfire.
Ensure the other engine mountings are good. Especially the one on the gearbox, as that has been disturbed when the clutch was changed. Might need slackening, jiggle the lump, retighten.

 

[Will2012Pop]

Update and progress hopefully.
With the car up in the air and the E brake off... I literally and figuratively got the wheels rolling in the right direction!
When the passenger side wheel was engaged and pulling everything was smooth like butta. Engage the drivers side wheel and my old nemesis, shudder shows back up.

So its obviously a drivers side issue. From underneath the engine shaking was pretty severe. The engine shudder/shake wasn't a fore/aft movement. It was shaking left/right between the front wheels which seems odd to me. There's no shake when it's in the reverse gear.

I had already replaced the CV joints and shafts once last week but went a head and swapped it out again just in case that the first replacement shaft had been defective. I wasn't that lucky. No change.

That leaves the stub shaft tri joint housing. I'm assuming it's worn and gotten sloppy in the forward direction but still good on the reverse side. Neither of my 2 replacement axles nor any of the axles I can find online designated for a manual transmission come with a stub shaft. The axles for the automatic transmissions do come with it. Any reason why?

Here's the snag.... I called prob 15 diff parts stores, searched thru at least 68.3% of every part store online and they all came back with "discontinued". Went to the Chrysler/Dodge dealers garage parts dept. Said it was unavailable/out of stock but they may be able to get one for me in about 45 days! They gave me part number 68110791AA.

Does anyone happen to know if the drivers side stub shaft for a manual trans is the same as the one for an automatic? (if so, I'll just get an entire axle assembly for an auto and rob the stub shaft off it). Any other part numbers that would be cross compatible? Any other ideas on where to source this part? Does someone happen to have a stub shaft that they want to part with?

Thanks, I truly appreciate the help!

 

[portland_bill]

If manual/auto were the same, they'd have the same part number. So there must be a difference.
The inner joint is likely to be the same both sides, so if a passenger side shaft is available, you could swap the joint, but that's a lot of work and expense. It'll be a rare car your side of the pond, but could there be any at breakers that will yield a shaft?