Slipping power spikes- new gbox and clutch already; is DMF gone?

[Praveen]

Hi,

After my bearings went on my gearbox at ~145k miles I replaced it with a 40k mile gearbox instead of fixing the old one. Replaced the clutch while I was at it. Not entirely sure if or how my mechanic resurfaced the DMF.

Couple months down the line I was driving intensely with harsh clutch drops etc. and car was handling it fine. Few days down the line I start hearing small knocking sounds whenever I put my foot down or let off the accelerator at low gears low speeds (1-3) @ low rpms. Not sure if gbox mount, engine mount, CV joint, diff?

But my main issue is the slipping power. When I keep my foot to the floor and hit ~2.2k rpm (around the max boost on my turbo) in higher gears (3-5) it is suddenly slipping. The rpms spikes by about 200-300 rpm, and if I keep my foot down the rpm stays there until the (clutch?) catches up. It still accelerates during this process but slower. It does eventually catch again and I can continue to higher speeds. With a lot of motorway driving it is becoming more of a challenge to be able to suddenly accelerate/ make overtakes etc. but is still handling alright. This is not full clutch slip where rpms max out. General clutch engagement is perfect at all speeds and all gears. The issue is just at full throttle and at that specific rpm range.

I am now beginning to get a sort of cyclic droning sound, quiet at low speeds, but loud from 70mph and much louder at 100mph. 

I've heard some Honda Civics which have had similar symptoms, and in one case was caused by a warped pressure plate. I did change this with a new one when I got the clutch and gearbox changed so not sure if it is this or not.

DMF (& clutch) was supposedly changed by last owner 25k miles ago.

Anyone had similar issues to this and if so what was the diagnosis?

I believe the 2 issues I have listed here may be separate issues i.e. one a bearing issue and the other a drivetrain issue?

Any help would be greatly appreciated! 

[Magnet]

Hello Praveen,

’.....replaced the clutch...’ 

Make of parts used? 

Kind regards,

Gareth. 

[Praveen]

Hi Gareth,

I used a Sachs Clutch kit.

Regards,

Praveen

[cliffcoggin]

Certainly sounds like clutch slip. If you routinely drive "intensely with harsh clutch drops" and "keep my foot to the floor" then it isn't really surprising that the transmission is failing.

[Praveen]

I don't drive routinely like that. That was a one off drive down some country roads.  I mostly do motorway miles so very little strain on the clutch.

Sounds like a clutch slip but with less than 2 months on that clutch it just doesn't make sense hence I suspect warped pressure plate or DMF issue.

Keeping foot to the floor in 5th should never be an issue in an ideal situation. 

Anyone else have any idea of what it could be?

[Magnet]

Thanks Praveen,

Sachs should be Ok, although I prefer LUK. 

From your description, I too could be excused for coming to a conclusion that your driving style would come under the heading of ‘enthusiastic’, and likely to put a greater than normal strain on the transmission. 

From what you say, I would have thought not changing the DMF would be regrettable - as would have been not investigating the possibility of an uprated or competition clutch assembly. 

Interesting comments on ‘flooring it’ on some country roads. In these parts, local farmers tend to break down?? in their tractors on some bends when they get wind of such things! so......

Hopefully you will get some more meaningful advice on here, but all I can suggest (which isn’t much) is to talk nicely to your wallet before extracting funds for a new DMF and an uprated clutch. 

Kind regards,

Gareth. 

 

[cliffcoggin]

Let's accept that you don't drive so harshly normally and get back to the history of repairs, which I am not completely clear about. Are you saying that there have been two new clutches recently? One that you did at the time of your gearbox failure and another that the previous owner did 25000 miles previously? Was the secondhand gearbox that you fitted reconditioned or overhauled in any way?

[Praveen]

Yes enthusiastic is more the word I'm looking for. And I do mean more on the straight roads, wouldn't risk it on bends. I only mentioned the harsher clutch drop as that was the only time I drove like that. It could be the reason which caused the issue, but it was not that harsh and definitely is something every car would be able to handle, especially when I had a new gearbox and clutch, hence the dilemma of I'm not sure what it could be. Maybe damage caused somewhere else in the system through shock loading but not sure what component.

Yes I put on the clutch when replacing the gearbox only since the entire assembly would be out anyway. The gearbox was not overhauled, it came out of a donor car and was in mint condition. Needed a quick turnover to drive back up North for work so didn't have the knowledge or time to properly look into uprated clutches and only just had enough time to get a gearbox shipped to me. I was unaware of refinishing DMFs and since the car had a new DMF 25k miles ago it was not something I thought about.

Car drove perfect no issues at all until the intermittent clutch slip issue came. 

Do you reckon it could be a warped pressure plate? Or is DMF the more likely culprit. I had receipts from last owner for DMF but can never be certain.

 

[Magnet]

Hello Praveen,

Apologies, and I can understand your disappointment in things not being what you would now want them to be. 

To cut to the chase:- ‘..warped pressure plate...’ ? Never really come across that, but quite simply, there would be no way of determining that without strip down. 

Faulty DMF after 25K miles? Possible, dependent on its quality (make). 

Of course, you did the right thing in replacing the clutch, and I would not argue about the normal quality of Sachs, and again, the decision not to replace a 25K DMF would also have been sound. 

Pessimistic, but it seems this has to be stripped again, and not to replace the DMF would be unsound. Resurfacing DMFs? Something new to me, but....always learning! 

If this were mine Praveen, I would be treating this carefully while I do some homework on recommended (uprated?) clutch and DMF assemblies, and then move forward from there. 

Kind regards,

Gareth. 

[cliffcoggin]

From what you have told us I really can't point the finger at any particular culprit. Look at the recent history.

The gearbox has done 40000 miles and has not been overhauled. It can not possibly be in mint condition at that mileage.

The DMF is now very secondhand, even if it was renewed 25000 miles ago.

The clutch is new yet it appears to be slipping. It should not be warped or significantly worn under normal driving conditions, but can easily suffer those faults if maltreated by harsh driving for as little as 20000 miles.

For the bearings to fail in the previous gearbox is unheard of in my experience, which suggests it had a very hard life. That in turn also suggests the whole transmission had been equally overloaded. All I can suggest is to remove the gearbox, clutch and DMF and thoroughly inspect and, if necessary, overhaul them.

[Praveen]

I am pretty sure it was a LUK DMF that went in. Will this paired with a Sachs clutch be any issue?

I believe the gearbox may have been leaking oil (potential crack) hence under-lubrication lead to failure of bearings especially with extensive motorway driving over prolonged periods of time.

Back to the slipping clutch, the fault continues but still remains intermittent.

These 2 forums describe the issue identically, with one issue being potentially addressed to the DMF while the other to a warped pressure plate:

https://www.avforums.com/threads/can-a-worn-dmf-cause-a-clutch-to-slip.2211444/

https://singletrackworld.com/forum/topic/clutch-slipping-or-something-else/

[Magnet]

Hello Praveen,

Thanks for coming back on this. 

Personally, I wouldn’t see any issue about using a LUK flywheel and a Saches pressure plate - both reputable brands.

A 40k gearbox should be fine, and coupled to a complete new reputable- brand clutch, all should be well, but unfortunately it isn’t. 

Warped pressure plate? - already commented on, and never too old to learn, but whatever way you look at it Praveen, the problem is likely to need to be investigated by stripping, so any possible cause can only be assumption. If it were mine, I would want to have complete confidence in the dismantler’s ability to investigate and fault find this issue. Certainly one clear step ahead fromsimply stripping an old unit out and fitting a new one in. 

Although I can understand your frustration with this, and you would like to come up with an explanation, I think there is potential in getting too involved in the ‘whys’ before we know the route cause. 

Perhaps you could keep us updated Praveen. Interesting! 

Kind regards,

Gareth. 

 

 

[cliffcoggin]

Praveen.

Like many on the forums you referred to I do not understand how a faulty DMF can lead to clutch slip, but then I don't have enough knowledge of them to give an informed opinion. I have read somewhere that the springs in DMFs can break and cause vibration.

Incidentally both forums suggested remapping as a likely cause of similar problems. Is that relevant to your car?

[Praveen]

Thanks for the feedback.

On the first time the issue occurred my mind went straight to the dampening springs in the DMF. Seemed to be the only thing which would make sense if the spring was jammed or snapped. However, as it was an intermittent issue I am still unsure of this. Is there any potential for foreign objects to be stuck in the spring itself or somewhere in the DMF assembly.

I assumed those springs would dampen rpm in the range of 50-100, not a whole 300-500, hence I was back to square one trying to see if it was something else causing the issue.

I will get it stripped and looked at as soon as possible. 

Thanks for all your help.