Notchy Gearbox When Changing Down

[ianchubb]

Following a complete transmission failure resulting in a tow in, I've just had a new clutch and DMF fitted to my 2006 RAV4 diesel 4WD.

Since then, changing down on engine overrun from any gear is really notchy in that the clutch seems to be barely disengaging. This happens only on engine overrun, e.g. on slowing into a roundabout or before taking a turning.

A blip on the throttle after depressing the clutch and before the downshift negates the fault however.

Engaging gear from neutral is fine, as is changing up. The clutch bite point is about an inch off the floor.

The independent repairer who did the job is saying it's not a problem with his work or the new parts, so I'm heading for a bit of a disagreement with him as the repair is warranted for three months.

Anybody got any ideas as to the nature of the fault please? so I can lean on the guy with a bit more technical reasoning.

Thanks.

[pgp001]

An inch from the floor doesn't sound right to me, like you say its probably hardly got enough travel to disengage properly.

I am sure someone on here will know what to look for.

Phil

[anchorman]

Who did this repair?

If not Toyota then they have probably filled the box with multigrade oil. In this case you will definitely have gear change problems. Bear in mind that early ones were a bit notchy changing down but the wrong oil is trouble.

[ianchubb]

Thanks for the responses.

Yes, I'm a bit concerned about the early bite point, but then why would it be ok changing up? as it's disengaging fine then.

I'll certainly ask the repairer ( a guy with an established business - he was the closest garage to tow it to who could fit the job in at the time) about the gear oil, but same question really...the problem seems to be with the clutch not the gearbox.

I understand clutches ok but am unclear about DMF's. Does anyone think the (new) DMF is suspect in all of this?

[Parts-King]

No. I suspect it's the oil as AM has already suggested, plus the box is not the slickest of boxes. Try the oil change first, cheapest option before faffing around thinking the worst

Kingo

[anchorman]

Its the nature of synchromesh, they change up better than they change down.

[Tech01]

Agree with everyone on this. First, get some 75W-80 into the box; heavier oil, particularly at this time of year, will make changes harder work. Secondly, get the clutch correctly adjusted: 1" off floor isn't right.

When you flip into Neutral, or blip the throttle (and thus ease the problem), you are effectively "double de-clutching" (Oldies, and some truckers, will know this driving technique), and this makes life really easy for EITHER a clutch that isn't disengaging properly, OR some synchromesh that has worn or been wrongly fitted.

It is often possible to change down on most vehicles, without using the clutch at all, simply by cleaver use of the throttle pedal: not recommended for daily use, though!

Let us know how you get on.

Chris

[ianchubb]

Thanks, all replies much appreciated.

I should have described the gear changedown a little more accurately. In fact, it's notchy coming out of the higher gear before passing neutral into the lower gear. In other words, it's similar to knocking the car out of gear without the clutch.

This is what makes me suspect the clutch rather than any synchro fault with the gearbox. The only thing about the gearbox that has changed since the new clutch and DMF was fitted is the gear oil, so yes this is something to check up on thanks.

And I agree that the bite point is too low. I guess it always will be lower with a new clutch plate with thicker lining, but is there an adjustment on it to bring the pedal up and remove any possibility of clutch drag?

[Tech01]

There is adjustment at the clutch pedal (for pedal height, free movement and for checking the "bite point"), but it should ONLY be set to the standard settings, otherwise there is are risks of clutch slip, drag or overthrow. If, at or very close to standard settings, the clutch action isn't right, then there is another problem somewhere.

With a new clutch plate, the bite point can seem to be rather near the floor, but this is usually because a new friction plate tends to be somewhat "grabby", before it acquires its usual polish.

The pedal height adjustments are in Section CL-2 of the Toyota workshop manual. Your workshop should have access to this. Let me know if you need the page posting, and I'll do it.

Chris

[pgp001]

Its the nature of synchromesh, they change up better than they change down.

Try telling that to my Austin 7 third gear !!

Phil