Hi @1eapplebaum

I changedchangeuel filter a couple of months ago for a new genuine part. Didn't make any difference.

I always run Shell v power 99 fuel.

 

Hi Lewis,

I've reread this thread, but especially this post. More and more it appears there is nothing wrong with the motor. I say that for several reasons, two of which -

you've captured enough basic engine data that now seems normal, normal enough that it is consistent with expectations of where it should be given age mileage of sensors, etc., assuming O2 sensors are original.
There are no engine fault codes. I have strong faith in these. If I don't see them, I don't worry too much myself.

Now back to other things and info from this post. It's interesting to me that you're seeing this issue around a certain speed and apparent gear position, Above, you're describing 3rd, 4th gear, but seems to be better when going faster and in fifth. Sixth?

Try this - drive to a place with no traffic, no stop/go. Get up to the sweet spot (speed and gear, 3rd, I presume), shift the trans to neutral for a moment, then throttle the engine the same way that you experience the "jolt" and observe the tach, Are you seeing the same jolt (or maybe flat spots) in RPMs? Of course you won't feel it, but can you see lags in RPMs that would cause the jolt if you were in gear?

If not, I think you can move past anything with the engine (but good DL exercises you did). At this point, you might need to refocus, maybe back on the trans. If we go there, the first question for you - do you have stock wheel sizes or aftermarket wheels? If aftermarket, are they staggered wheel diameters (front to back)?

 

I agree with regards to the engine except for what I experience with the exhaust note on coasting deceleration (how it sometimes isn't a smooth sound and there is constant burbling and spitting)

As far as I know the o2 sensors are original. Only sensors I've changed are the MAFs as I read a post with similar symptoms to some of mine so thought I'd give it a go. (No difference)

Definitely better at speeds over 40mph, 4th gear and above.

I'll have to try your experiment out, not sure if if will show anything as the actual gear shifts are fine it's just the throttle off throttle on.

I do have aftermarket 21" SSR wheels with 275 35 21 tyres however this issue was present on the stock 19s and no change noted after swapping to the 21s.

 

Tried the below @BWings and I don't feel it, I can rev the engine in neutral at 20-30mph smooth.

 

Lewis - this would put me in the trans now, or some other place in the drivetrain, especially since you seem to improve once getting into 5th and 6th gears.

I know you mentioned 6HPxx experience, likely the same place I acquired the experience with the 5HP/6HPs, in Jaguars. I had lots of them.

I would start questioning trans solenoids possibly, especially shifting around 3rd and 4th. I would at least do a fluid/filter change. Wouldn't be that expensive since you can do that yourself. Pretty much the same procedures, same fluid temps, etc. as the Jaguars

One thing I'd probably do out of curiosity before changing trans fluid, before you dump the old fluid is first do the setup to adjust fluid level starting out with a cold trans, engine running, go through the gear shifts, but while fluid is still cold, pull the plug and monitor the dripping to see if the fluid level is low (or high if fluid is rushing out cold). If you pull the plug cold, engine running you should see nothing coming out until you reach 40*C fluid temp (I believe from memory). I find that DIYers on these ZFs often try fluid checks and changes and end up really screwing things up. Maybe that happened before your purchase.

The reason I sked about the staggered wheel sizes, this car (this year) needs a "square" wheel/tire set, all four rolling circumferences matching BC the AWD is basically setup full time. If axles are constantly turning at different speeds, the slippage is going to be constant in the front diff clutches. Matching 21s wouldn't impact it.

 

Yes that's right, I had an XJ with the 6HP26 and try as I might I couldnt cure the 'lurch' 2-1 rollout shift and ended up selling the car because of it. Then owned 2 L322 Range Rovers also with this gearbox.

The actual gearshifts of the transmission are absolutely fine. This bump jolt whatever I'm feeling only happens lifting off the throttle to coast or pressing back into the throttle to continue cruising.

I recall seeing in the history that the trans was serviced in 2012 so probably about time it had another service. The oil level in theory should be correct as the specialist who fixed the car (all details in the other thread I linked) lost some gearbox fluid during the repair and had to top it off.

Doesn't mean it is actually correct however!

More things to go away and check

 

Hello @Lewis Barwick ,

Just some thoughts, and a few questions.

If you are driving with the transmission in "D" and are traveling at 30 MPH in fourth gear as you stated in post #1, and you lift off the throttle, the transmission should up-shift to the next higher gear, so fifth, and even into 6th, not hold the gear like it would in sport mode, or manual mode, so the question comes to mind if you are in manual mode, or drive ?

As far as the burbling and spitting, that is normal, especially when down-shifting, or holding a gear at higher RPM and letting off the throttle, you should hear my GT, snap, crackle, pop on down-shifting, now to be fair, I have the AWE Supersports exhaust with the track center section installed right now to go with the Supersports engine and transmission I installed, so the 6HP-28 may have a more aggressive down-shifting and holding pattern, but regardless, Even in D I get the burbling and rumble to a degree in certain gears, in sport mode lifting off the throttle to slow down, and the transmission automatically down-shifting to 3rd and 2nd, it is loud, S,C,P.

In post #7 I asked about the transmission fluid, along with the front differential and the rear differential, then in post #11 you state that you had the vehicle on the lift checking items, but you never reported back on to the transmission, or either differential's fluid level or condition, were these items checked ?

I will be heading out in a bit, and I will take note of how the transmission reacts in drive when cold and at operating temperature, especially from 20-30 MPH.

Johnny

 

Hi @Johnny Hotspur GT ,



I have the car in drive, cruising at 30mph the car selects fourth gear. If I lift off the throttle it will stay in fourth until the vehicles speed has slowed to a point where it shifts to 3rd.

This occurs for example when cruising at 40mph and releasing the throttle and slowing to 30mph (coasting with no use of the brakes to reduce speed) the rpm isn't high it's less than 2000 rpm. Doesn't always happen though as sometimes the exhaust note is a completely smooth burble as opposed to it spitting (almost sounds like small misfires)

I havent checked these fluids yet no. The only ramp I have access to is at my local friendly tyre suppliers, it is the 4 post alignment ramp so I can only really use it to quickly check the car not perform any work. I need to see if I can find a proper rent a ramp service local to me.

 

Hi @Lewis Barwick ,
I just took her out to run some errands, just at the right time, traffic time on 206, I tried all different scenarios and I see exactly what you are referring to as to the jolt, that could get annoying real quick, although the lightest feathering of the throttle seemed to help, to exaggerate it more, I held it in 1st and tapped on and off at about 10MPH, it definitely has a lag/jolt, I also experienced the same feeling if on the gas approaching traffic and quickly lift off the throttle, this happened in both 3rd and 4th, where lifting off when in 3rd it clunked going into 4th, felt worse doing the same lifting in 4th going to 5th, and this was low speed and rpm's, when she was cold and I lifted in 2nd and 3rd, it just moved up to the next gear smoothly, it even went to 5th at 35 ish..

I normally drive in sport or manual, I put a 646HP and 647TQ package in to have fun... 🤭

Johnny

 

Hi @Johnny Hotspur GT

Thanks for taking the time to note your thoughts.

What your talking about when testing in 1st is what I'm feeling whenever lifting on and off the throttle.

I have no issues with the other actual gearshifts just the throttle lag/jolt which does my head in as I can't drive the car smoothly. I rarely ever get on the power mainly just drive to work and cruise at the weekends.

Your testing suggests this could be normal behaviour for these cars. I think I'm drawing a comparison to the other car on my driveway which is a 40 year old Ford with a 3 speed automatic. No lag or jolt in that car!

 

Hello Lewis,

Haven't heard from you in a couple of days, maybe you've had to step away from it...I know how that is.

I keep thinking about you!

After all these posts I'm really past the engine operation (besides, anything that would cause a jolt or lag would produce a powertrain fault code and since you don't see one(s) at all, puts my mind in the trans).

A few of us now hope you can validate the fluid level in the trans.

I've read again, the symptoms you've described in post #s 1 and 42.

Then I started thinking about the torque converter. There is a possibility here, especially since you're describing a lower RPM/lower gear shift where the jolt occurs, then seems to improve at faster speeds (and maybe different RPMs).

I pulled this article for your perusal. Take a look at it, especially the section titled - The Torque Converter has 5 Important parts, and the section titled - Torque Converter Problems and give special focus to items #1 Slipping, and #2 Shuddering. Can you relate your actual condition to any of these possible symptoms described in slipping and shuddering? BTW, take note one of the first items of mention in the article is verifying fluid level.

https://www.aamcoblog.com/Article/Si...-How-to-Fix-it

Hope to hear back from you.....All the Best,

 

Hi

It sounds like the transmission need initializing, there is a procedure from ZF but its hard to find. You first have to check the fluid is correct and then you delete the old adaptions then re-learn, this cause jolting particularly when the transmission gets hot. I'll have a look to see if I can find the procedure.

 

Yes I've read about that procedure @GH Bentley. It would be worth a go.

I'd like to reset the transmission adaptions but as far as I am aware this isn't possible on 2005 cars.

Ive tried VCDS but it just gives errors when attempting to reset.

 

Hi Bwings,

I've been driving other vehicles for a bit but back looking at this now.

I'm going to see if I can secure the use of ramp to first check the transmission fluid level and then service the transmission (last done in 2012 according to the history)

I've read the article you linked and I don't have shuddering or slipping. The only things I feel are a very slight vibration in the car when cruising at 30-40mph 4th gear and also same thing when cruising at 70mph.

On a cold start as I drive onto the main road 30-40mph there is a pulsating feeling like someone's tapping the throttle on and off but this improves when warm.

I did take the car to a specialist for this and they said the car drove normally and they couldn't fault it?

I noticed this morning that in Park with a warm engine if I hold the revs at 900rpm there is vibration in the car until I move away from 900rpm.