Hi all

So, my 3ltr td6 (2006) with the GM gearbox is, surprisingly, playing up!

In the morning, I pop it into drive but it takes about 30 seconds or so to engage. Once engaged it doesn't do it again until it's left for a few hours. The longer I leave it, the worse it is.

I've serviced the gearbox using Texaco ATF 389 which is a dexron 3 and replaces the texamatic that was in the gearbox originally. I followed the correct filling procedure (level, temp, fill while running etc etc). I had a good look at the fluid that came out, which was nice and red, without any sparkly bits and only a light paste on the magnet.

I've also popped a new 020 varta battery 110ah on the truck as well., as the previous battery was 80ah and was so small it was rocking in the compartment lol

Although the gear changes are lovely and smooth, it's not changed the original issue of not selecting drive initially. It also holds onto 4th and jumps around the gears a little and I need to ease off the throttle to allow it to change up to 5th, which was also happening prior to the oil and filter change.

What do you folks think is causing it not to engage drive and also, why is it very sensitive to throttle changes (is TC not locking??)

Cheers

Jim

In Manual mode you should be able to select 1st or 2nd gear to set off from stationary (or 1st, 2nd & 3rd in Low Range). Does it make any difference to the engagement delay if you switch to Manual mode and engage 2nd gear, for example?

If the engagement delay is due to a lazy Forward Clutch, one possibility is that the moulded rubber seal on the Forward Clutch piston is taking on a ‘set’ when left over a period of time (e.g. overnight) which causes the seal to leak when first started from cold. The seal then becomes pliable again once warm and conforms to the shape of the drum, stopping the leak.

Click image to enlarge

Click image to enlarge

Thanks for the reply Phil.

Appreciate the information, yeah my initial thoughts were that oil was draing back into the sump and needed time to re-pressurise before it engages drive. So I'm guessing it requires a rebuild at some point and also, is this going to damage anything else?

I popped it into manual 2nd gear and it went off as it should. Put it almost immediately into D and it kept going......a temporary fix, thank you!

Hmmm. Manual 2nd uses the Forward Clutch too, so I think that puts the kibosh on the leaky moulded piston seal theory.

I would be interested to know if Manual 1st gear exhibits the same engagement delay as selecting Drive. The difference between the two is that the Low & Reverse clutch is applied in Manual 1st to bypass the Low sprag. A big difference in engagement time would point the finger at a faulty Low sprag.

Ahh ok that's interesting and judging by that diagram, it's very blimmin complicated lol

Ok, I'll see what happens in 1st. I've tried it before and if memory serves, it was quicker than D but still slipped.

I'll report back tomorrow, thank you.

I can't comment on the drive delay fault but regarding general gear selection and behaviour is that the gearbox will up-shift readily with no load on the gearbox and equally down-shift under very small increases in either load, or very small increases in throttle position. The normal slip speed is around 2,500rpm on my gearbox under modest acceleration, going higher if more pedal is applied.

This makes it very 'fussy' when driving on local roads with any inclines. Engage cruise control at 30mph and expect revs to go up and down with any change in load on the gearbox, not refined and quite annoying. Most of this is due to the relatively high slip speed (my terminology) of the gearbox which in my opinion is intended operation so that when the vehicle is being used for its other purpose i.e. off-road driving the engine maintains max torque engine speed regardless of gear engaged?

Mine will engage 5th gear at below 50mph depending on load and lock up at around 50mph. Once lock up is engaged it will hold it down to around say 45-48mph. Hope that helps. Current: 2003 TD6 HSE. 161,000 miles
Previous 1993 Classic 3.9

Hi Phil

So i successfully pulled into residential traffic this morning by popping it in manual 1st, straight from cold (overnight). Slight slippage but id say the same as 2nd gear yesterday. I didn't have to over-rev it at all, it was just slightly less responsive that it is when warm.

Hope that helps?

steve k wrote:

Hope that helps.

Hi Steve, yes it helps massively, thank you. As you can tell by my name, I've come from Pajero's, where this situation is identical. Everyone I've owned (4) has done this. The reason i thought this was unusual on a RR is that my e60, which has the same 3 litre M57 paired with a ZF6 gearbox is as smooth as butter and changes gear exactly when its supposed to and none of this indecisiveness when moving through gears, especially when under load, on a slight incline, where it holds on to 4th (2300-2500 rpm) until you back off the throttle.

If i turn the music up and don't look at the rev counter, i don't notice it at all lol, the kids on the other hand aren't massive fans of Motley Crue, Skid Row or any other 80's rock bands, so i cant use that tactic consistantly

Glad to give my thoughts! Ive had 3.0 petrol e60 with 6 speed ZF box and completely different as you said.

I wasn't going to also mention that the engine noise is intrusive at lower speeds but now you have I recently found that the two ventilation tubes that feed into the bottom of the big fuse box under the bonnet had been disconnected from the fuse box. The two pipes provide car ventilation via the drivers side footwell. The feed to the box is in line with the brake pedal (black plastic ribbed round hole) and the return from the box is hidden behind the kick panel where the bonnet release lever is. The open pipes were effectively transmitting engine noise directly into the cabin! re-fitting them has not made a drastic difference but everything helps.

I suspect they were disconnected in the past to move the fuse box for some engine work. The easiest way to check if they are connected is to loosen the box mountings and lift it slightly and have a look. The pipes are ribbed approx' 30mm diameter and retained with jubilee clips on stubs fitted to the box. I re-fitted mine with a lot of difficulty this way. With hindsight if you peel back the wheel arch liner its a lot easier. Current: 2003 TD6 HSE. 161,000 miles
Previous 1993 Classic 3.9

Ahhh ok, i never even considered that. Thank you Steve, i will add that to the list of jobs....which is growing larger and more expensive by the day lol but the drive is fantastic, so its worth it! L322 2006