Gearbox. Again.

The gear box had a 3rd/4th synchro spring fail about six months ago.  The symptoms were immediately recognisable, having suffered the same failure in 2004, that resulting gearbox rebuild triggering the rebuild of the whole vehicle.  The symptoms then were the complete jamming of the synchro unit, locking out 3rd and 4th.  This time around, it happened on the way to work, and I had to drive almost the whole 25 miles in second gear and overdrive (gently, given the overdrive previously killing third gear), but the shattered remnants of the spring cleared themselves just before finishing that journey, regaining the two gears.

There was some intermittent ticking from the box, which I assumed to be the spring pieces gradually freeing themselves from the synchro unit and impacting the casing, though it could have been those parts going through the teeth.  Draining of the gearbox oil produced a lot of shards of shattered steel, mangled from going through the gear teeth.  Since then, another short bout of ticking occurred and the synchro rings lost some effectiveness, leading to occasional crunching of gears on 3rd and 4th and a sloppy and notchy feeling gear change.

109-gearbox-damageI bought replacement synchro hub springs for the unit and a new main shaft (due to worn output splines) some time ago, and have finally got round to fitting them.  I’m not doing a big rebuild thread here – I have previously covered gearbox rebuilds in detail.  Suffice to say that more spring shards came out with the oil and another spring had indeed failed, leaving just the one, hence the weak synchronising effect and odd feel.  Disappointingly, I found the big brass bush inside the second gear had pulled its fixing dowel out of the main shaft,the oil grooves inside the gear dragging the dowel around the bush, wrecking it.  So, these have also been replaced.  I have a photo of the damage to that bush and of the one remaining synchro spring.  You’ll see that the spring has worn where it slides against the baulk ring leg (as it’s meant to do), and it has worn pretty thin in the middle.  I suspect this is the cause of the failure of the other two springs and for the failure ten years ago.  It is not uncommon, and seems to occur at about 50,000 mile intervals, give or take (the amount of gear changes you make will be the main factor).  I’m told it’s possible to replace these springs through the top of the box without dismantling the whole unit, but I wasn’t able to do it last time.  The guys at Dunsfold Land Rover seem to know how to do it, so I’ll ask them next time, if I don’t need to address any other gearbox issues.

I plan to refit the box tomorrow.  The Roverdrive is remaining off the vehicle – the input coupling has a little spline wear, and was the cause of the gearbox main shaft’s spline wear.  This was from the nut coming loose on the main shaft because the grub screws didn’t bite hard enough.  I’m also feed up with its rattly selector lever – the rose or Heim joints on the operating rod get loose and rattle.  Not expensive, but a cost I don’t need.  Add to that that I found yet again the front case has snapped a locating shoulder (having already replaced the casing for new when the last one did the same thing – the new version with the large oil slots for the front bearing is just too weak) and the fact that it cooks the transfer box oil, turning it dark caramel coloured in just a couple of thousand miles, I’m getting fed up with the Roverdrive.  I think that the 3.54 diffs will allow me nearly the same mpg because the 109 is overgeared with them and the overdrive together, and going back to a standard transfer box input gear eliminates the energy losses from bearing and gear friction in the overdrive.  Back to simple, robust, standard systems.  If I do ever get 4.11:1 ratio diff gear sets, then the overdrive will be useful again, but not until I get yet another (fourth) front cover, returning to the original spec cover that I wish I had never exchanged for “upgrade”, if I can convince them to supply one to that older spec (just a little less milling).

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Comments

  1. Nick, sorry to hear that you have had more troubles with the gearbox. Also rather worrying to read about the roverdrive issues as I was about to buy one! Can you let me know how many miles you’d done on the roverdrive before you experienced the problems?

    After our last discussion I went ahead and bought the large diameter tyres (33″), the same as my wifes truck, in the hope of improving gearing for commuting while avoiding the need to go to 3.5 diffs. I reckon I’ll still need an O/D though for faster motorway trips. Sounds like I’d be best just getting a fairey unit? My wifes truck has a fairey and in conjunction with her 33″ tyres/4.7 diffs has done 14K miles now with no gearbox or overdrive issues despite those boxes being far from perfect to begin with.

    Was the roverdrive quiet? The only issue we have with the fairey is the whine it makes and apparently they even make this whine when in good condition?

  2. The Roverdrive is quieter than the Fairey, though mine is making more gear noise than it used to after nearly 50,000 miles. Oddly, the gear noise is more with it disengaged than with the original transfer box input gear, suggesting that the tooth profile on the Roverdrive is slightly out. To me, they look a little flat, too like isosceles triangles rather than having a near elliptical profile. The coupling to the gearbox main shaft is more robust than the Fairey (as long as you get those grub screws to bite in the collared nut that replaces the original castellated nut), and that is my main concern about the Fairey behind a Tdi or V8. However, I think the new Roverdrive front casing (same as the original, but with slots milled into the sides of the nose to expose more of the front bearing) is too weak, shearing its locating lugs at the top. The original design had just the one slot, so the location was done by a near-continuous ring, not an arc at the bottom and two lugs at the top. The redesign was done to increase oil flow, but it also reduces the amount of oil sitting in the overdrive. I think it’s a backward step. It is also more prone to cooking its oil than the Fairey, even with the finned sump plate on the transfer box. You could get around this by using synthetic oil, but finding synthetic EP90 is impossible – you’d have to use W75.

    I’ll keep the Roverdrive in storage for future use – once the RRC is back in regular use, the 109 will just be used for trips where speed and economy will be slightly less important. I’d like to fit 4.11 ratio diff gears, but that’s expensive, so I might just go back tot he 4.71 original ratios, but either way, they’d be low enough for the overdrive to be useful again, at which point it’d be work me replacing those selector heim joints and the front cover, if I can get one made to the early spec. I’d also fit an electrically pumped oil cooler and feed into the rear of the casing to make sure the aft most bearing is fully lubricated and to try to keep all the temperatures down. I’m thinking along the lines of some copper brake pipe, coiled for the cooler section, with an electric fuel pump from an ignition fed live, with unions tapped into the lower aft face of the transfer box, below the filler plug/dipstick and in the centre of the aft end of the overdrive.

  3. Thanks Nick.

    Depending on the final routing of my exhaust I may well be adding a transmission oil cooler too. I’ve seen a nice Mocal system on Demon tweeks website with pump, thermostat and cooler, not cheap though. The Series 2 routing of the exhaust pipe places it well away from the gearbox but the later Series 3 routing puts it slap bang next to the box and on long journeys I found my oil cooked many times in the past. I’m hoping to have a manifold fabricated to fit the 200Di and take the exhaust out via the Series 2 route though which will keep the temps down a bit.

    Ian

  4. I didn’t know about that oil cooler kit. I’ll take a look to see if it’d work and if the price is reasonable. There is plenty of room on my 109 to mount a cooler under the tub floor. Above the cross member behind the hand brake drum would be good for the straight RR auto box cooler or similar as there is no chance of damage from stones or a flailing prop shaft. The airflow should be adequate with all the turbulent flow around the chassis.

  5. patrick chilipamushi says:

    Nick,

    I have a 109 rover series II. I cant get first gear. There isn’t just play on the lever to engage.

    please help.

    Regards,

    Patrick

  6. Hi Patrick.

    Can you get second gear, or is that locked out too? If the lever won’t move over fat enough from 3rd and 4th, then you need to adjust the stop bolt on the reverse inhibitor flap (spring loaded flap on the front of he reverse gear selector shaft) so that it is less horizontal. If you can get to reverse but 1st and 2nd shaft doesn’t move forwards or back, then I’d suspect a price of dirt or corrosion jamming part of the detent and interlock system inside the top cover. If it is just first gear and you can get second, then I’d suspect a failure inside the gear box that will require a full rebuild, though it could be something as some as a piece of debris in the bottom of the transfer box brea her tower at the back end of the top cover in line with the back of the middle selector shaft. That seems unlikely, though.

  7. Hi Nick. I am locked out of 3rd and 4th and while I realize it’s probably the same synchro spring issue was wondering if the detent springs in the top could cause the same issue? Thanks in advance. Andrew

  8. Hi Andrew,

    A jammed detent should prove that the select shaft from moving if the ball bearing is jammed in the shaft’s groove, so it is worth checking before removing the box. The biggest part of the job is removing the tunnel and floor panels (especially the driver’s side, as the pedals and hand brake get in the way – I take the hand brake lever off, which is just two nuts, without disconnecting it’s linkage – remember to chock the wheels if you do that). It’s not waster effort, though, as you’d need the panels out to remove the box anyway.

    With the panels removed, you’ll see the top of the box and it’s removal cover. You need a 7/16″ spanner for the small bolts on the detent retainers, selector shaft seat retainers and the front of the gear stick mount, and mine has 15mm head bolts for the back of the stick mount and top cover nuts, though 9/16″ may be typical.

    I have an explanation and photos of how the detents all work in the FAQ section on here. When reassembling, make sure everything is scrupulously clean. Oil will be splashed about and get i to the workings as soon as you test it after rebuilding, so you can reassemble dry if you choose, though I prefer to lightly oil the shafts first.

    Strip the top with the drain plug in place. If a detent ball drops inside, it’ll end up inside the hollow plug, rather than dropping out and bouncing off to be lost. Draining the oil through a sieve will catch any fragments and soon determine if you have a broken leaf spring, though yours may have jammed and not yet shattered.

    If you do clear a shattered spring, you can drive on one or two remain ing springs, but they will fail sooner. Missing springs will also mean the synchro baulk rings are pressed less firmly and evenly against the cones on the gears, so the gear change will feel lighter but be more likely to grind teeth. Remember when refitting the detent springs that the heavier one is for reverse – it is very common for people to assume it goes under the brass plug retainer in the middle and use the two lighter springs symmetrically, but that leads to heavy detent on 1st and 2nd but too weak a detent on reverse.

    Good luck with it.

  9. Just looking this issue up , I have driven over 500 miles in my series 3 over Christmas without issue , however since getting back the gearbox (although easily selecting gears and still not causing any issues) had started making a grinding noise in 1,2,3, as if something was churning around. I drained oil and one of these clips fell out , (in two pieces ) now this is my short term dilemma , im thinking of filling the oil back up (it was very low) and seeing how it goes short term. As I look at it the clip may have fallen off and been grinding between the cogs causing the noise and if the noise stops that would be great , I can then at a later stage replace the clip , as I say the gears change easily , that clip could have fallen off years ago . I am also going to try replacing the clip without removing the gearbox when replacing the clip , I know it has been done in the past.

  10. Hi Neil,

    You have nothing to lose by trying that. The springs will all need replacing, and the sooner the better, but it’s not urgent. The fact that one let go shows they’re already worn, and missing one of them, the baulk rings will not have even pressure when changing gear or enough pressure to be fully effective. This means that while the gear lever effort is reduced, the likelihood of crashing hears is increased unless you make a conscious effort to ease into gear. But the other springs will be well on their way out by now, and once they go, 3rd and 4th synchronisation will be lost and you’ll need to double declutch until repaired.

  11. when reversing over a 4 inch high wall an allmighty crack came from underneath resulting no drive in 2wd high ratio but will drive in 4wd high and low any thoughts please

  12. Hi Phil.

    I’d imagine you have broken something in the rear axle. The gear box and transfer box are using all the same gears, whether 2wd or 4wd, so anything wrong in there would affect both cases. The housing on the front of the transfer box is the 4wd housing, and that merely contains a dog clutch that connects or disconnects the front output shaft to the transfer box main shaft. For the front axle to be driven, the transfer box must be working normally.

    So, the bang is in the back and you are driving in 2wd on the front axle. Be careful and gently for two reasons – first, the front axle is weaker than the rear and not intended for taking the full propulsive load, and second, the rear axle will be grinding metal and compounding the damage.

    Hopefully, it’ll just be a rear half shaft, most likely the right hand side, and probably sheared at one end where the splines begin (usually at the diff end). Less likely, and more expensive to fix, is a broken rear diff, but you could source a good second hand unit to keep costs down. Alternatively, a broken diff could be an opportunity for an upgrade to a locking or ATB diff, if funds permit.

    Fingers crossed it’s just a shaft – that is very common on 88″s.

    Nick

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