Amazon: Overdrive not engaging

[222s]

Cheers for the clarification

[940_Turbo]

Originally Posted by 222s

Just to clarify (as my understanding of how the internals work is limited) & apologies if this is a stupid question, but presumably the the clutch linings and cone clutches are essentially the same mechanism? It isn't slipping under engine braking which is listed in the green book as also being due to worn or glazed clutch linings, so would that suggest that those are likely to be ok?

There are two clutch linings, but a single cone clutch. There is a lining on the inside and the outside of the cone clutch.

The cone cutch is spring loaded, when the overdrive isn't engaged the cone is in its rearmost position. There are 4 springs which push the inside clutch linings onto the annulus (effectively the output shaft) in the overdrive. This provides straight through drive.

When you engage the overdrive the hydraulics force the cone forwards, against the springs and the outside clutch lining lock solid against the steel brake ring you see sandwiched in the overdrive body. The sun wheel of the planetary gears is now locked, forcing the annulus to rotate about the planetary gears faster than the input speed.

If the pressure is too low then the cone clutch won't lock against the brake ring properly.

[222s]

Yesterday, I changed the oil, cleaned out the strainer, checked and set the solenoid adjustment, but it still won't work at all. <insert appropriate expletive here> The strainer had some stuff in it when removed, but was far from blocked. However, much of what came out of the filter appeared to be some kind of fibre shavings (clutch lining??), if that gives any clue as to what may be wrong. The gearbox oil (engine oil as per the manual, rather than regular gearbox spec) was also quite grey and stank...

Tbh, I'm now going to go down the route of fitting a recon o/d, as there is no way I'm delving any further inside the unit as that will be well beyond my ability. Thank you all for the advice to try to get it going - very much appreciated, & it's good to know that it actually needs the new unit, rather than being something really simple!

I'm not sure yet whether I'll be able to do the swap (it's a case of having somewhere to do this, as I don't have a garage or driveway), but if I can sort that out, is there anything particular to watch out for when separating and refitting the overdrive from the gearbox? The green book makes it sound all very simple, but I'm sure I've read on here about others having had trouble removing the o/d.

Cheers!

[Derek UK]

Paul. How much do you know about the previous oil maintainence history of this GB/OD? Grey could mean aluminium particles but could also be from a moly additive. Slippery additives not good for an OD. Stinky oil could mean that hypoid has been used, that has a bad smell. Again not correct for GB/OD but might work for a while.
Certainly sounds as if it will have to come out though. Dropping the whole box and od the best idea.
Yes, apparently there are "tricks" to getting the OD off. Residual oil pressure can stop it from coming off and being able to turn the output flange helps to get the gears in line. Have the GB in neutral when removing is good I think. If you are going to get the recon done by Overdrive Services Sheffield 0114 248 2632 they'd be worth a call before you try and remove it for advice. Having all the gaskets and seals on hand before it comes back is good. There are a couple of small O rings at the to top rear joint I think which are often missed and can cause leaks.

[222s]

Originally Posted by Derek UK

Paul. How much do you know about the previous oil maintainence history of this GB/OD? Grey could mean aluminium particles but could also be from a moly additive. Slippery additives not good for an OD. Stinky oil could mean that hypoid has been used, that has a bad smell. Again not correct for GB/OD but might work for a while.

AFAIK, it's always had engine oil in it, and that's what I've used when topping up (in 15/50 flavour) - I've never put anything else in there, precisely because of the o/d. It's covered about 120K since '94 and I believe that the o/d hasn't needed any attention during that time (certainly not since '02 when I acquired the car), and would probably have had it's last oil change in '07, when the gearbox was rebuilt.

Originally Posted by Derek UK

Certainly sounds as if it will have to come out though. Dropping the whole box and od the best idea.
Yes, apparently there are "tricks" to getting the OD off. Residual oil pressure can stop it from coming off and being able to turn the output flange helps to get the gears in line. Have the GB in neutral when removing is good I think. If you are going to get the recon done by Overdrive Services Sheffield 0114 248 2632 they'd be worth a call before you try and remove it for advice. Having all the gaskets and seals on hand before it comes back is good. There are a couple of small O rings at the to top rear joint I think which are often missed and can cause leaks.

Thanks

[222s]

The overdrive is now out, thanks to the invaluable help from a friend. The original plan was to remove the whole gearbox, leaving the bellhousing on the back of the block, but the 3/8" hex bolts holding the gearbox to the bellhousing absolutely refused to shift, so tried removing the gearbox with bellhousing attached. That didn't work as there wasn't enough width to pull the bellhousing back far enough, and the engine couldn't tilt back enough to lower it below the tunnel. However, it was possible to tilt it down enough to easily access all the bolts holding on the overdrive.

If all goes to plan, it will be sent off on Tuesday to Overdrive Repair Services in Sheffield. In the meantime, I can now get at the borked reverse light switch (that is jammed on) and have a couple of weeks in which to tidy up some of the paint underneath. Incidentally, the gearbox crossmember dropped off the moment it was undone & didn't have a jack under it - the mount had sheared off & quite a long time ago from the look of it, so I'm hoping the new one will eliminate the odd clonk that makes itself known occasionally....

However, a surprising thing I learned & which may be of use to others was that one of those material oil filter removing tools is ideal for undoing the top of the gear lever tower (so the lever can be removed), as a large adjustable spanner just wouldn't shift it, and I didn't want to risk rounding off the flats.

[Burdekin]

This is my job for tomorrow and also sending it off next week, hoping it goes well. When speaking to the guy at the Overdrive repair place he said quite often D type ODs from Amazons can be quite knackered and recommended splitting the OD myself for a look into the condition. Seems like the recondition price can range from £285 up to nearly £600 if totally knackered.

[222s]

Originally Posted by mitch1971

When speaking to the guy at the Overdrive repair place he said quite often D type ODs from Amazons can be quite knackered and recommended splitting the OD myself for a look into the condition. Seems like the recondition price can range from £285 up to nearly £600 if totally knackered.

Yup, that's the prices they told me. However, I'm not intending to sell the car any time soon, & need it back on the road ASAP so just hoping it isn't damaged beyond repair! Wondering what makes them different from the Ds in other cars though, as they offer exchange ones for those. Perhaps Amazons are the only D equipped cars that mostly still see proper usage, and thus are more likely to have more serious wear?

I'm not dismantling mine, as tbh I wouldn't know what I'm looking at! However, I suspect that something nasty may have happened inside based on a few things that we spotted when getting it out..... Either way, I'm interested to know what's wrong with it.

[Derek UK]

While the OD is out it's a good idea to check/replace all of the female or ring crimps on the mini harness. As well as being properly crimped to the wire they also need to fit a male crimp snugly. They can get a bit loose over time, especially if they've been yanked off a few times. Loose crimps can give the OD drop out problem noted here but from what you say Paul, there is some metal debris in the unit which doesn't bode well.
This info relevant to Mitch's OD refurb too.

[Burdekin]

Hi Paul,

FYI I read the other day that the top two studs where the OD bolts onto the gearbox/OD spacer should have copper washers otherwise they will leak.

My OD should be finished this week. When I rang on Friday it had been stripped and all that is needed is pretty much the standard overhaul which is a relief. Hope nothing serious is wrong with yours as well.