Building a stronger series gearbox can it be done ??

[Aussie80inch]

In preparation to eventually putting a 200 tdi ( which I'll pull down and reco as required ) into my 80 inch I want to rebuild a good, strong series gearbox.

Ive read how you can adapt a disco gearbox to fit into a series 2 or 3 but with the s1 80 inch I don't have the luxury of space.

I don't want to cut the chassis ( galvanised ) or shorting the prop shaft any more ( running Salisbury diff )

So my question is, can a series gearbox be built to take the added strain of a tdi motor.

Does anyone do like a rebuild kit etc with the stronger components ?

Here in Australia ( maybe it's the same in the uk ) I've had many friends get there L/R gearboxes professionally rebuilt for them to fail in under 500 miles!!.

When asked why all said that the replacement parts ( synchro etc ) though new where rubbish.

So can it be done, is there suppliers out there that Can supply stronger components or do I just keep a good gearbox or two on hand if and when one fails

At the moment my 80 inch has a early series 3 with 2a bell-housing with overdrive

As always any advice and help is greatly appreciated

[Chicken Drumstick]

I think the main answer is driving style. The Tdi isn't really all that potent and the 80 is pretty light.

If rebuilt boxes are failing in under 500 miles, that's more than just blaming stock components, something else is a foot.

This has a Series box in it (from a 2/2a IIRC) and a 3.9 V8 and only ever gets abused. Think the box has been in there for 15 + years or something like that.

[ejparrott]

Series 3 box with the one piece layshaft is the strongest, but there's nothing you can do to make it any better.

Gearbox failure is not simply because a TDi is bolted to the front of it. I've had it for about 7 years now and have no confirmed damage in gearboxes caused by the TDi

[missingsid]

I was under the impression (maybe incorrect) that the S2 onwards with synchro were weaker than S1 boxes??

Confused!

[Snagger]

There was a widespread myth that SIIA boxes were the strongest, SIII boxes having weak synchros. It is possible that the late (Suffix D and on) SIII units are stronger than the earlier units due to slightly altered synchros, but I highly doubt it. However, the SII's lay shaft is weak because of the splines and abrupt changes in section creating stress points. The SIII unit is better by far, and late units are improved a little further by having ECM gears that help the synchros remain in gear better under torque (both positive and negative loads) and having a much improved reverse idler gear bearing (rollers instead of a cheap bush that wears the shaft).

Professional recon is more con than re - I have had a few and they used a lot of scrap parts and cheap pattern parts, bodging things up to hide the fault but making something with very low longevity. Do it yourself properly with Genuine Parts and it'll be fine, as long as you don't drive badly. But as I said, don't fit 3.54 diffs as well as your overdrive - the Tdi input torque and the high resistance of that combined gearing rise will kill the box at some point (apart from 3.54s driving horribly on a Series with 7.50 tyres). Keep the overdrive on it, though.

[jai_landrover]

V8's driven normally are very easy on gearboxes how often do you change gear in a good v8? How many times do you change gear in a tdi?? Lots!!

A decent freshly built gearbox with quality parts should be fine I would have thought. If they're failing soon then there must be an issue

[Joshua81]

I agree with "Old Hand" - try to use quality parts than It should be fine.

[LaRoNut]

There was a widespread myth that SIIA boxes were the strongest, SIII boxes having weak synchros. It is possible that the late (Suffix D and on) SIII units are stronger than the earlier units due to slightly altered synchros, but I highly doubt it. However, the SII's lay shaft is weak because of the splines and abrupt changes in section creating stress points. The SIII unit is better by far, and late units are improved a little further by having ECM gears that help the synchros remain in gear better under torque (both positive and negative loads) and having a much improved reverse idler gear bearing (rollers instead of a cheap bush that wears the shaft).

Agreed.

If you are that concerned about the strength then I would recommend you source a gearbox from a Santana Series 3 or 4. It has the same dimensions as the Landy box but is substantially stronger with ribbed casing and heavier gears. Bellhousing fits the V8. Its a 4 spd box and you can fit an overdrive. You could also consider the LT77 perhaps.

[Anderzander]

This is interesting stuff.

If there is no scope for improving the box, and putting aside sympathetic driving for a moment, are there other options to reduce the load put upon the box ?

For example would a DMF on the back of a 200TDI into a series box bring any benefits ?

[discomikey]

I, for one, don't understand this age old "series boxes all die in weeks behind a tdi" thing. Just make sure you look after it and have degree of mechanical sympathy.

[Snagger]

The Santana boxes share the same innards as the suffix D SIII box, so is no stronger.

[deep]

I read this thread with interest. Over the years, I had come to the conclusion that the Series IIA box was stronger and I see I was wrong. Or was I? It seems Series III boxes are very prone to popping out of first or reverse, either under load or on the overrun, when the mileage gets up, while Series IIA boxes seem to soldier on. Popping out of gear is worse than being weak, in my eyes...

Either way, in line with what was said above, I really believe transmissions do much better with sensitive drivers and pretty much any Land Rover gearbox can take a certain amount of work. None of them are actually made of putty, are they?

[Snagger]

The suffix A SIII box has the same reverse gear idler shaft and bush, which is the source of the problem, as the SII. The later SIII boxes went over to roller bearings which stopped the shaft tapering wear and the jumping issue.

Other than originality on an older vehicle you that want to keep standard, there is no advantage to a SII box over a SIII.

[deep]

The suffix A SIII box has the same reverse gear idler shaft and bush, which is the source of the problem, as the SII. The later SIII boxes went over to roller bearings which stopped the shaft tapering wear and the jumping issue.

Other than originality on an older vehicle you that want to keep standard, there is no advantage to a SII box over a SIII.

Thanks for that. The other issue I have come across is first gear falling out on the over-run but that might not be common (though I think I've seen it in two boxes, from clouded memory...). All good to know.

My Series IIa has a 3.3 litre six in it and the previous owner wasn't kind to the car but the box is still very sweet. I don't think any of them are that bad are they? Now I am about to start using a LT77, which had a terrible reputation. I wonder how that will pan out!

[Snagger]

Diesels can be hard on transmissions because of the rough nature of the engines. V8s deliver more torque, but as it is delivered smoothly, it doesn't shock or hammer the transmission.

The biggest issues are: are the parts genuine or cheap pattern manufacture, is the oil replenished frequently, and does the driver subject the transmission to shock loadings by clumsy clutch and throttle use? Avoid all three, and you shouldn't have too much of a problem.

However, you can end up demanding too much. I have a Suffix E box, which is a LR Gen Parts exchange unit. Mine is made from a suffix A case (so retains the carp suffix A reverse shaft and gear) with Suffix D shafts and gears. All the bearings, bushes and seals and the main shaft are the same for all SIII suffixes, and the lay shaft has minor detail differences to do with gear mesh for the main shaft gears, not to do with strength.

I broke two teeth off third gear by using it in conjunction with 3.54 diffs. It took six months, but having used the transmission and engine for several years of motorway and laden mountain driving without a glitch, I don't think the failure was coincidence. The teeth that sheared off were either side of an oil cross-drilling, so there was a small inherent weakness that was overloaded. With the box repaired, I suffered a second unrelated failure of the leaf springs on the 3rd/4th hub, which seems to happen at roughly 50,000 mile intervals as the springs wear on their centre detent. That was rectified and all went well for another six months when the lay shaft bearings started howling. Prompt stripping down before any failure revealed part seized bearings and bright metal flakes inside the bearing cover that is seen inside the bell housing. I'm not sure where the shards came from, but I suspect they were from the bearing itself as no other damage or contamination was found. Incidentally, this occurred immediately after an oil change with 75W90 semi synthetic oil, which lacks the anti wear sulphur additive of EP90, suggesting to me that you must stick to the old EP90 whatever anyone tells you about the superior qualities of 75W90.

So, my recommendation is use the standard box, whichever you have, and use 3.54 diffs OR overdrive, but not both, and stick religiously to EP90, at least in the main box.

[LaRoNut]

The Santana boxes share the same innards as the suffix D SIII box, so is no stronger.

I wish you all the luck in the world when you interchange parts from a Santana IIIA and a Series suffix D gear/transfer box.

There are only 3 oil seals that are common between them, nothing else! I have rebuilt and serviced both types. Santana IIIA is much stronger than a Land Rover SIII suffix D.

It was common in ZA to fit all kinds of V8 engines to the Santana, with no problems at the gearbox end. The production Series IIIS that was available here '82 to '91 was also fitted with 4.236 Perkins and 3.54 diffs, no problems. All IIIS Land Rovers had the Santana Box and was the local version of the Stage 1. Over 6000 of these vehicles were produced in ZA.

I would suggest the OP fit a Santana IIIA gearbox, or consider a LT77.

[Snagger]

Is that the LT85 type unit? I'm talking about the Santana split case unit that separates from the transfer box and looks like a ribbed SII or SIII box.

[CR88]

Hi,

I think that everything regarding possible solutions are already mentioned.

I bet in the Santana IIIA gearbox or LT77. They are stronger than any series gearbox.

The reason of my reply is to clear just one point. Gearboxes are structural dimensioned to the torque, not power. More power implies more heat, that can be solved with an oil cooler, like in some R380 gearboxes.

All the TDis (200 and 300) have at least twice the torque of any series engine. This don't mean that driven carefully and having a decent gearbox it will last for some time, but the series gearbox aren't made for such torque or power.

If you want something reliable, for everyday use not for weekend fun, don't install a TDI in series gearbox.

[ejparrott]

Sorry, completely disagree. MY 88 has been my daily driver for about 7 years now, with a TDi driving the series gearbox and transfer box, Fairey OD, 3.54 diffs and 7.50 tyres. She has been extremely reliable, I have no confirmed gearbox kills in all that time. There is one question mark hanging over one gearbox that I must get over to Phil and have a look at, but it's not a confirmed engine kill until I know what's wrong with it.

[Chicken Drumstick]

How people drive and what they use the vehicle for, will make a big difference though.

Personally I have no doubt a Series box can be reliable behind a Tdi. And as a rule we are more likely to read about failures, rather than successes. As few people will post up on the internet about not having a problem.

That said, plenty of people break series boxes with the stock 2.25's. There is no denying the box can be fragile. Therefore anyone who has success running a Tdi on one, should probably be seen as more of an exception or rarity than the norm.

Lets face it, the LT-77/R380 are theoretically rated for 380nm/260'ish ft-lb of torque. Yet a stock Tdi can eat them too.

[CR88]

Sorry, completely disagree. MY 88 has been my daily driver for about 7 years now, with a TDi driving the series gearbox and transfer box, Fairey OD, 3.54 diffs and 7.50 tyres. She has been extremely reliable, I have no confirmed gearbox kills in all that time. There is one question mark hanging over one gearbox that I must get over to Phil and have a look at, but it's not a confirmed engine kill until I know what's wrong with it.

Your transmission configuration is one example of a solution that can be overstressed easily. High gear ratio combined with taller tires isn't the ideal for the transmission.

Nevertheless, your feedback is valid, it's based in your own experience and I know other examples like yours near to me.

But, generally, I like to follow numbers, and these are the facts:

• 2.25-litre petrol - 120 lbf·ft (160 N·m) @ 2,000 rpm
• 2.25-litre diesel - 103 lbf·ft (140 N·m) @ 1,800 rpm
• 200Tdi / 300Tdi - 195 lbf·ft (264 N·m) / 210 lbf·ft (280 N·m) @ 1,800 rpm (Defender)

The torque of the 200/300 Tdi is, more or less, the double of any Series's 4I engine and this is superior to any design/project safety margin that I know. This kind of over-engineering doesn't make sense.

There are other points to be mention as well, like lubrication, syncro design, gearbox case strength, points that when the series gearbox was design were not so developed as now or when the LT77 or R380 were projected.

But I reaffirm, depending on the gearbox condition and in the driving pattern it can last, but I don't trust in this solution.

[mickeyw]

Sorry, completely disagree. MY 88 has been my daily driver for about 7 years now, with a TDi driving the series gearbox and transfer box, Fairey OD, 3.54 diffs and 7.50 tyres. She has been extremely reliable, I have no confirmed gearbox kills in all that time. There is one question mark hanging over one gearbox that I must get over to Phil and have a look at, but it's not a confirmed engine kill until I know what's wrong with it.

I agree with EJP.

While not a DD, I had my 88" V8 for nine years without any transmission problems. It had a 3.5 V8 on a series 3 box, series 3 diesel clutch, 3.54 diffs and 265/75R16 tyres. I did a fair bit of heavy towing, (drum brake fade is baaad news when coming to a roundabout with a loaded trailer), and plenty of off roading. Worst of all I drove it rather hooligan stylee, because it really did go very well.

There was no need to cane it in low gears - it pulled so well right up to top gear, and at scary motorway speeds.

I sold that on in the end, with no transmission problems that I knew of. My wallet still feels the relief. I probably could have bought a few gearboxes for all I spent on petrol

[Soren Frimodt]

I thought I'd give my 2 cents on the matter

I love the Series gearbox and has not had any problems with mine either, in any of my Series trucks, however I'm a sucker for lightweight so none of them have been very heavy. this obviously helps a tremendous amount.

With regards to LT77 and R380, honestly are they really that much better than a Series box? There are loads and loads of people that have killed the lt77 behind 2,5NA's over the years, and many other people have changed the R380 as well. Heck Ashcroft makes a living reconditioning these two! I personally have changed/ helped change more LT77s than Series boxes, by far!

If you wan't a strong box and like to look at numbers, then either the TorqueFlite 3 speed auto out of the old Rangies or the LT95 are both extremely robust gearboxes and go at next to nothing because they simply are so reliable and nobody wants them because they are not 'fancy' enough and don't have an overdrive gear. But if you have a Series your already used to no overdrive, and with much more engine power than stock you'd be able to just run a taller gearing. I had a measure up on my dads 101 engine/gearbox combo a while ago. (Short bellhousing LT95 and 3,5RV8) and it was only 8cm longer than a SIII 2,25p with Series box! And a heck of a lot more potent and stronger. I probably will never fit such a gearbox to my 80" though, as I still love my Series box, super easy shift compared to any other box fitted to LR's and much lighter.

[CR88]

ok ok, hit me no more!!!

the only advantage that the series has is the weight (500 kg less at least, 109 vs discovery), and justifies your feedback.

my concern is more technical and yours more practical.

my experience with my series gearbox isn't the best with the original engine, so far I cannot give a feedback that supports the Tdi in series gearbox

[Snagger]

CR88, as I said, I only had problems when I added 3.54 diffs to the overdrive and Tdi. The double gearing increase was too much resistance. I have heard of many people breaking SII and SIII boxes behind 2.25 petrols and diesels.

You're right that the Tdi has a lot more torque than the SIII four pot, but not vastly more than the six cylinder, and I think they shared many parts of the gear box. But you have to remember that back then, things were built to last and with less accurate design stress modelling because of the lack of computers and greater design margins because of the lack of computer controlled machining equipment, the stress capability of the transmission would have a much greater margin than a modern unit has over its matched engine.