2.8 Auto Braking By Itself While Cruising To Halt

[Alex]

As title my 2.8 crd auto 2007 is braking sharp when cruising to halt, well just before coming to full stop. Also jerky when crawling traffic. Car doesn't move off when put in drive without reving on flat. Gearbox shifts through gears perfectly. I did autobox filter and atf4. Worked perfectly for last year. Could it be brake disc or caliper? Although it doesn't pull to either side under braking. No funny noises just bit clunk as if slammed on brakes just before full stop.

[bignev]

Hi Alex, yes it could well be the brake pads very very low, grabbing on the discs, wheels off and caliper off to reveal them properly

[Alex]

Thanks bignev. From what I can see pads look nearly new. I'm taking wheels off this morning to investigate. Keep you guys informed. Thanks for response.

[andyb2000]

Does sound more like braking to me than the gearbox, my bet would be calipers sticking, especially rear, so when it happens, or perhaps do a quick drive, let it slow down a few times then go and CAREFULLY touch the allow wheels, see if any of them have got hot or warm to the touch, might save you taking each wheel off in turn!

[Alex]

Well I'm stumped. I pulled the caliper and brake pads off out of the equation. Started car up on axle stands and tried gears. Shifts nicely from park to reverse to neutral to drive. Once in gear wheels don't move i have to rev in drive or reverse to get any movement from wheels. Intermittently it'll brake sharply when lift off accelerator. Definitely think it's gearbox related now.

I've ordered new disc and pads anyway. Caliper push back smoothly and relatively easy so that's fine.

[andyb2000]

Good test, so yes eliminated that, so yes it does sound like gearbox/torque converter, but not a fault I've heard of before. Going to start reading up!

[bignev]

Oh dear, that sadly is a new one. Have you checked recently the atf fluid level, only a guess.

[Alex]

Just tried my obd2 thing with torque pro app no fault codes found. Can anyone please remind me how to do key dance? In case Torque pro app isn't reading gearbox faults.

[Alex]

Yes regular check but checked again today.Atf fluid looks nice pink and in warm zone on dipstick. Thanks

[Alex]

Thanks Andyb2000. I keep trying to re word my problem in Google search not having my luck.

[Alex]

Oh and I've had battery terminals off for good hour and shorted across them to reset gearbox computer. No change unfortunately.

[andyb2000]

Hi Alex, it sounds more mechanical than electrical to me so I'm going to suspect unless a specific gearbox fault you'll not get far with codes and electrical diagnostics.

Keydance is 3x into ACC position leaving it there at last switch for codes to be displayed, have a pen and paper handy!

 

Unfortunately this is the opposite of most issues with a worn gearbox (slippage), so I think next steps would be an auto-gearbox specialist to take a look or at least describe the problem to them and see if they're aware of it or have found this problem before.

[Alex]

Hi Guys. Right been to an automatic specialist. Met up with two lovely older professionals, who new their stuff and they're baffled. Never seen anything like it. They did series of road tests and plugged it into their computer. They're pretty sure mechanical side of gearbox is sound. As lock up only occurs in 1st and reverse and only when engines running. They think it's electrical fault. I've come back with car. The only faults found are abs related, I'll get print out for exact wording. Was something like abs speed sensor,wheel sensor on passenger side and undervoltage sensed on abs pump.

I'm busy fitting new front discs and pads. Cleaned up abs sensors and reluctor rings. As I've had bad earth problem before. Solved by adding new thick cable from negative to starter. I'm going add new earth straight to tcm and abs module in case......

[Alex]

Other than that its look wiring between tcm and gearbox next to check.

[andyb2000]

Wow, that is indeed a strange one, yes it's amazing what an older-school technician can spot and work out, always worthwhile!

 

So you've narrowed it down to 1st and reverse, so initial shift. When you put the lever into N position will it freewheel without friction (Maybe one to try again with the car up in the air to see what amount of rotation you get).

ABS sensor/wheel speed sensor is a common one and easily replaced. I also had a stored code a while ago for undervoltage on pump, believe that was from a stall/cut-out as we cleared the fault and it's not come back.

 

Hope you can narrow it down and do feed back as it's unusual for sure.

[QinteQ]

41TE info from allpar.

[Alex]

Thanks for that QintQ, I'll give it read.

Thanks Andy. They found intermitten bindup in neutral 1st and reverse and only when cars running. If you're coasting along in neutral just before final halt it grabs as if sharp braking. The old guy did it again but cut engine and car didn't do it. I've disable abs by pulling fuse and did test drive problem still persists.

I've replaced front discs and pads plus had back ones off to re adjust handbrake shoes. I did rear new discs and all pads including new shoe kits last year November.

I've fitted more earthing.

Nothings helped so far actually feels like its getting worse.

Next job is opening wiring loom to look for obvious damage.

Sure I read someone had problems with faulty alternator causing some sort of interference with gearbox. What do you guys think?

[Alex]

Reading some of that QintQ link.These box's rely on hydraulics to control gear selection. Do guys think that might be block filter/s in solenoid pack?

[Alex]

After yesterdays 30 min drive back from automatic specialist I thought check dip stick. Getting upto 70mph for some bits. Atf was in warm zone on stick and oil was barely warm. Gearbox just felt warm. One of back brakes was hotter than rest that's why stripped and re set handbrake shoes.

[SpAwNtoHell]

Hello, i think you look at the issue in the wrong place... i think your transmision is fine, but your transmision works/shifts/reacts based on engine torque, which i think now you have a lack of. I got this issue on a different car before... if you have someone who can read in interpret engine live data you will fknd out probably that one of the engine sensors does not relate properly to the ecu the right parameters. In my case was the maf sensor tho was not giving any error codes, but is reading was wrong and i was low on torque. That is the reason that you need to rev it to start moving. Worth considering my point i think as like you i even went as far at getting gearbox checked 4 different places and i was about to change it with a recon one.

[blackvelvet]

SPAWNtoHELL has got it right here.

If the symptoms occur even in neutral,, as you say it did. the problem is not the transmission drive.

If the problem occurs with the calipers removed, it's not brakes.

The problem is low revs,.... engine related.

[Alex]

Hi guys. Thanks for all responses.

I read each and carefully consider what your saying. This car is not suffering low revs or torque.

On advice from specialist I open loom between gearbox and TCM Etax. Test every wire for continuity, even sensors wires all checked okay. Wires also looked in good condition.

 

So I bought a new solenoid pack and fitted it. Car worked perfect for a day. Reverse and drive self propelled once I lifted of brake. Gear shifting through all gears smooth like silk. Next day after short run back to same problem. Car wouldn't reverse, rev rev rev then it would bunnyhop back. It's like the hydraulics not holding low/reverse clutch in.

 

I've also changed the two speed sensors. Stuck ohm meter on new and old same reading so not those. Plus my Speedo has always worked fine.

Gear selector is showing each gear as it's selected and you can feel it go into gear.

 

My thinking now it's either crap in atf4 blocking new solenoid pack or faulty TCM. Remember the automatic specialist found no fault codes on Tcm.

Would auto electrician test tcm?

 

I'm going to pull solenoid pack off and crank engine see if floods rubbish out.

 

I've seen a lot of talk of tcm relay in fuse box. Mine doesn't seem to have tcm relay in fuse box. it's got lift pump relay in that position in fuse box.

[Alex]

Can't seem to reset gearbox computer,tcm eatx. Its 2.8 crd 2007 voyager 4 speed.Does anyone know how? Ive tried battery off etc.

All stuff I've read says to do "quick learn" my obd2 reader doesn't do gearbox.

[Alex]

Just add. Through all this mine hasn't gone it limp mode, don't know if that's a good or bad thing.

[SpAwNtoHell]

How did you checked torque out of curiosity? 

 

re step what you done when you changed the solenoid pack...

Edited April 25, 2018 by SpAwNtoHell

[Alex]

Hi Spawn. There's no bog down feel to rpm when trying reverse or 1st(low). It's sort of a catch release feel, sort of neutral with sudden with catches and if revs are up it wheel spins. No feel of resistance on engine.

But you've got me retracing steps done while doing solenoid pack.

1. While waiting for pack I unplugged solenoid plug, 2 x speed sensors and TCM big plug. Undid loom wrapping between and traced all wires to these. I did continuity test to see if any wires where brocken non where. Replugged everything and wrapped loom wiring again.

 

2. Battery was reading 12.45V, pulled out car and stuck it on charge overnight.

 

3. Cleaned around old solenoid pack then removed it. Cleaned gasket off. Bit atf4 spilled when pack was free.

 

4. Fitted new Borg Warner solenoid pack and new gasket.

 

5. Refit charged battery. 12.7v

 

6. Started car. Kept foot on brake and slowly cycled through gears to get rid of airlock.

 

7. Test drive 5 miles forward and reverse 100%. Success car works better than ever. Next morning take my Daughter to school 3 miles come to reverse at school back to same problem. In fact feeling worse.

 

Things I've noted. After cars back to problem.

 

1. While obd2 was plugged in today with app on my phone. Showing voltage 13.7v. Now is that normal coming from computer. I mean at battery for charging,normal but isn't car computer suppose to regulate that down to 12v?

2. I've had car running pulled negative off, car still runs so to me alternator fine. 13.9v read while cars on with battery in, no button mod.

3. I've read somewhere faulty diode in alternator could interfere with Tcm.

 

My thinking is maybe battery was fully charged so kept regulator on alternator from adding current- car 100%. After sitting overnight and cold start alternator kicked in and messed with Tcm.

I've pulled battery for over night charge 12.65v read before removing. To test this mad theory tomorrow.