Td5 Autobox downshift clunk!

I know it's not always manners to make suggestions to tradespeople how to do their jobs, but greasing the tailshaft is a five minute job. Have you made the suggestion to him? It's a cheap option compared to a new MAF.

Also check he's getting a ridgy didge MAF. General opinion of aftermarket cheap MAFs is they're not worth the effort. You could also try just unplugging the MAF and taking a quick spin. If they're not connected, the ECU defaults to some standard values that will work well enough to tell you if the MAF is faulty.

IMO that clunk is caused by accumulation of more plays along the transmission line but mainly due to the transfer box and rear diff, it's easyer to get closer to the answer if you have CDL, then drive it with locked central diff and if the clunk is noticeably reduced then that's it even more relevant with the rear prop removed in this case better leave the gearbox alone and concentrate on the transfer box and diff... the front diff is possible to be involved as well but more common the rear

No disrespect sierrafery , maybe a language misunderstanding, but if you drive with cdl locked on the bitumen for too long you will end up with more than a slight clunk to worry about , unless you meant to say disconnect front or rear propshaft first, then you can work out which end is giving problems, fwiw I end up doing d2 diffs on average 3 fronts to every 1 rear , the front tends to cop a lot more abuse.

You are right, my apologies, i forgot to mention to drive it with locked diff only for test, a short time to see if the clunk goes away or not, i didnt mean to drive it so on a long run, sorry

Quote:

---

Originally Posted by Ceebrady

Now I realise that the engine is also different meaning that the sensors fitted to this engine are not the same sensors that were with fitted with the original gearbox, is it likely or even possible that this could be the cause of my issue?

---

I presume from this statement you have gone from a 10P to a 16P engine. Did you also change the engine ECU, Transmission ECU and airbox lid sensor/wiring? (10P and 16P ECUs are different)

Gazk

Thanks for your question. By 10p and 16p engines am I correct in assuming these are this is the difference seen in the EU2 and EU3 motors? Neither of the engines has all had the later model head nor the heat exchanger that runs across the front so I believe that both were the earlier type based on that assumption that both the 10p, The replacement engine was originally in a manual vehicle.

Thanks

Engine number prefix 10P (1999-2001) is the EU2 spec. Prefix 16P (2002-2004) is EU3 spec however not all 16P engines have the EGR cooler. The one I have dismantled without the cooler had a manual transmission and that was how it came from the factory according to a VIN check using microcat.

Thank you gazk
Thank you everyone who is contributing to this solution.

Have a question about the modulation pressure reading that you see when using a nanocom evo. The value that is shown at this place, on my vehicle modulates between zero and three, is this value in bar? What range of values do other people see during normal driving operation?

I checked the black box solutions website but they didn't specify the units for this value.

Also does anyone know if the value shown is the pressure picked up from the sensor, or is it the pressure that the ECU is intending to make via a modulation of an output signal?

Anyone's help on either of these matters would be greatly appreciated.


I am so the car is back from the local Autobox guy and there's no change in performance.

It's a strange thing with that modulation pressure cos there is no input in the ECU for such value, it must be a calculated value based on the voltage output to the valve and also it's addaptive so it can be different from one car to another.... i insist though that you should make a short drive test with central diff locked if you have it or lock it with a spanner if you have the spigot cos it might be some mechanical wear in the driveline not gearbox fault especially that it happens on down****s it can be the symptom of a backlash, quite common... for electronic faults the EAT is quite well covered by the diagnostic protocol and the Bosch GS8.87.0 is reliable so if it was something like this you should have got warnings and fault codes logged IMO.

if you insist on the autobox some info here http://www.aulro.com/afvb/discovery-...uild-link.html

Thanks Sierrafery

I will get under and remove one of the tail shafts, probably do the front first lock it up and taking for a drive.
In that post that you provided the link for The other user talked about the other diagnostic tool providing the modulation pressure to 2 decimal places I would therefore suspect that it is in bar.
The other thing that looked a little bit strange where looking at the autobox via the nano com was that the value for requested torque never change from 99, does everyone else have this same reading?

Thanks