Jump to content
Aussie80inch

Building a stronger series gearbox can it be done ??

Recommended Posts

ok ok, hit me no more!!! :unsure:

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

I really hope you don't take it as an assault on your opinion, you have every right to have your own opinion, and every right to throw mine in the bin if you feel like it! I just always feel like the more opinions you get, the more likely you are to find a pattern in peoples experiences which often leads to easier/better decision making.

The one scenario where I could see myself fitting a LT77/R380 in a Series was if I had one as a DD for my 84km/day commute, would only do it if I had upgraded the steering and brakes though, as I feel like the speeds a Series (especially a SWB) are capable off stock, suits its handling (or lack thereof) very well.

Share this post


Link to post
Share on other sites

I really hope you don't take it as an assault on your opinion, you have every right to have your own opinion, and every right to throw mine in the bin if you feel like it! I just always feel like the more opinions you get, the more likely you are to find a pattern in peoples experiences which often leads to easier/better decision making.

The one scenario where I could see myself fitting a LT77/R380 in a Series was if I had one as a DD for my 84km/day commute, would only do it if I had upgraded the steering and brakes though, as I feel like the speeds a Series (especially a SWB) are capable off stock, suits its handling (or lack thereof) very well.

Soren, isn't a question of assault, it's more a question of stubbornness. For many reasons I prefer solid solutions to a pair of trousers made of patches. I have a 69 88in that if I could I would to go with it everywhere, and for that reason I try to match the best and most solid solutions that match my pocket.

I have the same point as you, opinions should be as different as possible, that make the debates more rich.

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.

Snagger, I have this directive in my life "don't swap the new by the good one", maybe in English you find a saying that suits better my idea.

Regarding the new stuff, and diesel engines, in the past 25 years these engines developed in a way that everybody get surprised.

Since the diesel engines by concept are limited to 4000 - 4500 rpm, the increase of power was done by the improvement of the torque. Thanks to that, gearboxes had a revolution as well. Nowadays it's easy to find 2.0 liter diesel engines around 400 N.m, much more then a Tdi or 2.25 diesel. The great thing is that these new engines are quieter and smoother and deliver the power more gradually.

The trend is smaller engines and beefy gearboxes.

Regarding design margins, I'm in complete agreement. Old school material was design to harsher conditions. But I believe that this last sentence can be discussed in a new topic. "Old vs New, which is more dependable"

Share this post


Link to post
Share on other sites

Have a look at how many clutch and gear box issues afflict the TDCI Defenders and Discovery 3 at relatively low use and get back to me! ;) But I can tell you the old stuff is easier and cheaper to fix, especially in the middle of nowhere.

Share this post


Link to post
Share on other sites

I really hope you don't take it as an assault on your opinion, you have every right to have your own opinion, and every right to throw mine in the bin if you feel like it! I just always feel like the more opinions you get, the more likely you are to find a pattern in peoples experiences which often leads to easier/better decision making.

The one scenario where I could see myself fitting a LT77/R380 in a Series was if I had one as a DD for my 84km/day commute, would only do it if I had upgraded the steering and brakes though, as I feel like the speeds a Series (especially a SWB) are capable off stock, suits its handling (or lack thereof) very well.

regarding your commute and 4 speeds,

as i have previously mentioned, i run the same setup as EJ: 4 speed, overdrive, 3.54 diffs and 235/85 tyres.

i used to travel from Shropshire to hull and back every weekend (~270mile round trip). on tuesday im off down to milton keynes for a job interview. (~210 mile round trip)

the thought of that many motorway miles doesent phaze me one bit. this gearing no doubt puts more stress on the transmission than standard setup, however even with the severe lack of maintenance (i know, i know, but i am a final year engineer so i dont have spare time) the gearbox copes fine. even with my seemingly pointless need to drive everywhere sideways

in fact, im quite looking forward to getting out on the motorway! not done it in a few weeks now

Share this post


Link to post
Share on other sites

By the way, in your post at the top of this page you raise your concerns over raising the gearing by having 7.50 tyres. Tose are the standard tyre for the 109 and an option for the 88, and the transmissions on the 4-cylinder models are identical, regardless of tyre size or wheelbase. It really is nothing that should worry you.

  • Like 1

Share this post


Link to post
Share on other sites

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.

Worth mentioning that the original design for the gearbox dates back to the (pre war) Rover P3, intended to work with either the 1.6 four cylinder, or a 2.1 litre 5MB version of the six cylinder.

Fair enough it was upgraded through its life, but by the time it ceased production in 1985 the basic design was over 40 years old.

I do recall reading a bit more on the subject of strengthening Series boxes before, and seem to recall the main problem with them was that -generally- trying to upgrade the weak points caused probems elsewhere.

The LT77 has reputation for being a carp box, and did have a few design flaws to start (plastic oil pump gears for example) but actually isn't an awful box considering. The main problem with them in Land Rovers was the output shaft /Input gear wear issues when connected to an LT230, something eventually solved by cross drilling the gear to allow some lubrication of the internal splines.

A Tdi can be made to work with a Series box, as can V8's and a variety of other things, but no matter what your experience you can't argue that runnning a 4 pot diesel with twice the intended torque output through it wont have any effect on how long it lasts. Driving style can however make a difference to how long it will keep going.

Share this post


Link to post
Share on other sites

The short LT 77 from a 90/Defender it's ideal to an 88 in.

Share this post


Link to post
Share on other sites

Das, the point is not that there is anything wrong with going for an LT77 or stumpy R380 - they're quieter, smoother, leak-free and certainly stronger. The point is that it simply isn't necessary, and it's a lot of work. If you like the challenge of the conversion and can afford the time and parts, great. I'd prefer one to the Series box and an overdrive, but I can't do it without losing the vehicle's identity (too many other changes). Does that worry me? No.

Share this post


Link to post
Share on other sites

Hi to all that have replied it seems running the series gearbox behind a 200 tdi is a much debated subject I do have a couple of question some mention running 3.54 diffs why is this a better ratio

At the moment my 80s set up is 265 x 75 x 16 tyres with 4.7 ratio diffs and a overdrive on the series box

Salisbury rear and rover front

Share this post


Link to post
Share on other sites

Nick and I have opposite views on the 3.54 diffs, and we've come to the conclusion it's because I have an 88 and he has a 109, thereby a half ton difference in weight - we can't consider my 109 any more as I now have an LT77 coupled to the 200 anyways.

My 88 pulls 30 very nicely in third and OD, and she's never complained yet. The 3.54's do mean that I'm higher geared in low box than if I used a HRTC from Ashcrofts and the 4.7 diffs, but it's never worried me, she seems to cope just fine.

Share this post


Link to post
Share on other sites

My 88 pulls 30 very nicely in third and OD, and she's never complained yet. The 3.54's do mean that I'm higher geared in low box than if I used a HRTC from Ashcrofts and the 4.7 diffs, but it's never worried me, she seems to cope just fine.

with the same setup, i have to mirror these comments.

Share this post


Link to post
Share on other sites

Das, the point is not that there is anything wrong with going for an LT77 or stumpy R380 - they're quieter, smoother, leak-free and certainly stronger. The point is that it simply isn't necessary, and it's a lot of work. If you like the challenge of the conversion and can afford the time and parts, great. I'd prefer one to the Series box and an overdrive, but I can't do it without losing the vehicle's identity (too many other changes). Does that worry me? No.

I don't see it as a requirement to have an LT77 to run a Tdi, my point was more that the basic design dates back to the 1930's, and whilst it was probably over engineered for the application then -and with some development was made tougher to help it last better in the Land Rover- a Tdi is still putting a lot more through it than it was ever designed for.

Yes it works, and if that's what you want to run in your vehicle then I'm not gonna knock you for it, but whatever way you look at it the engine is more than capable of overloading the box, and a reduced service life or increased likelyhood of failure shouldn't be a surprise if it happens.

I'm not the sort to get up on a high horse about what you should or shouldn't be doing with your truck, just offering an opinion based on my knowledge and experience working in the trade over the years.

Share this post


Link to post
Share on other sites

The Series box doesn't just "work" behind a Tdi, but with a short life span. It is entirely adequate as long as you don't drive like an idiot or combine too many gearing increases. Overdrive, 3.54 diffs, HRTC or big tyres are fine with a Tdi, just not in combination. That's based on over 20 years of using mine, running it up and down the Alps fully laden, not just motorways, and knowing plenty of people in clubs running V8s and Tdis. I also know a few people who regularly blow their boxes behind a 2.25 diesel. It is all about the driver, not the box.

  • Like 1

Share this post


Link to post
Share on other sites

I rebuild gearboxes, diffs etc for a living and I trained with Land Rover as an engineer.

I personally went through 7 late 2a gearboxes in 3 years, no i don't drive like a idiot but occasionally use a trailer and load my 88 up to the brim with logs or Scouts .

The series 2a box in real terms has to many places for faults to start. Layshaft, loose fit on input gear into transfer box, rear layshaft bearing is awful ! far to small. A bloke i worked with has worked on Land Rovers since the 60s and he was rebuilding gearboxes that were 2-4 years old all the time. I love the series gearbox its period and great, but the 2a isn't smooth and this causes internal parts to smack against each other like the gears on the layshaft splines, you may not feel it happen but this is my view and i feel its the cause of the issues. A series 3 box suffix D is far smoother and allows gears to mesh faster and more gently. Along with the layshaft being one peice. My best mate has a TDI behind his and its been faultless. but make sure you run 80w/90 not EP90 synthetic gear oil is far better.

Thing is a series gearbox will generally always work unless a shaft breaks or teeth shear off but i bet 75% of people here actually have gearbox faults and not know, but because it was built in the "good old days" it continues to soldier on. The series box is a design from the 30s and originally was designed for 30-50 bhp max. Land Rover made it slightly better but not a lot.

Unlike a series transfer box which is good for 500nm of torque. only rebuilt a few series transferboxes but hundreds of lt230s

V8's are kind on gearboxes as their torque band is even and a TDI's isn't. Hency why the last many years.

Sure people will disagree but i've rebuilt in excess of 200 series gearboxes and 300+ LT77/R380s

And a Suffix F-G-H LT77 is no weaker than an R380. Early lt77s were poor but still better than a series box ,hence why morgan and car manufactures didn't start using them still suffix C when they got bigger gears and bigger bearings. thing is my 200tdi disco did 225k on its original LT77 is that really that bad on miles and the sychro on 2nd went mainshaft was like new. lets see how many modern cars are even on the road at 225k

Needless to say I have a suffix H lt77 defender box with series transfer box in my 88" with a 200tdi VNT and massive intercooler,3.54 diffs, uprated half shafts and 1 ton brakes on the front with a heystee bigger servo. No more worries, tow big trailers and you can quickly pull out of junctions and not have to worry about breaking stuff. I use mine for work and i do a lot of miles a year so my situation is different to most but thats my opinion

  • Like 1

Share this post


Link to post
Share on other sites

Whilst in general you most likely very correct about a V8 being softer on gearboxes mine has a RRC flywheel and S1 gearbox/transferbox and 3.54 diffs. which is great offroad but on road accelerating hard the gear changes are dreadful if I forget to let the revs die down. The flywheel will luanch the vehicle forwards with a bang if I forget. Still only broke the one layshaft in 25+ years of ownership! Probably break it next week now!!

Marc

Probably repeated myself!!

Share this post


Link to post
Share on other sites

What other gearbox would cope with a 200 mile round trip at 80mph COMPLETELY dry of oil? And still only need a couple of bushes, and synchros, totalling less than £50?

they're not the quietest, smoothest, or most easy to drive with, but they take a lot of punishment ant when they do fail, it's usually something that will still get you home!

Plus a blindfolded buffoon could rebuild a series box, so if it does go wrong, it's not too much of an issue anyway ☺

Share this post


Link to post
Share on other sites

What other gearbox would cope with a 200 mile round trip at 80mph COMPLETELY dry of oil? And still only need a couple of bushes, and synchros, totalling less than £50?

they're not the quietest, smoothest, or most easy to drive with, but they take a lot of punishment ant when they do fail, it's usually something that will still get you home!

Plus a blindfolded buffoon could rebuild a series box, so if it does go wrong, it's not too much of an issue anyway ☺

Oh, I don't know; that split ring on the main shaft can be a pig to get right!

Share this post


Link to post
Share on other sites

Oh, I don't know; that split ring on the main shaft can be a pig to get right!

Don't say that ! As a blind buffoon I was feeling quite encouraged !

Share this post


Link to post
Share on other sites

coming back to this, i wouldn't guarantee this mod would actually make the box stronger, but certainly much quieter in most cases.

as most series box rebuilders will tell you, the bearings within the box are largely fairly decent, and big, which is good, with the exception of one bearing. The rear layshaft bearing. in comparison to the rest it has 2 main flaws:

  1. the bearing is rather quite small, especially when compared to the other bearings in the box
  2. the bearing is absolutely rubbish, the roller cage is a rubbish design which loosens up allowing the rollers to move around. This is the "chatter" you can hear when using low down torque in 1st to 3rd gear.

as a result, it gets noisy fast and can't cope with torque. This could be the initial cause to further gearbox failures, however that hasn't definitively been proven. What i propose to do is to source an alternative bearing, of a much higher quality than the standard one, possibly of a larger outer diameter too (if possible)

Combine this with the use of proper high quality bearings around the rest of the gearbox (NSK, GKN etc) then i have reason to believe that you will end up with a series box which is rather quite quiet and should last a lot longer than normal, especially when pitched behind a rough, torquey engine such as a 200 or 300TDi.

when i get the time i plan to build such a box, ensuring the endfloat on the 1st and 2nd gearsets on the mainshaft is perfect, and the use of this uprated bearing idea.

If i have enough desposable income at the time i then plan to destructively test the idea using an engine and a tractor dyno or something, and see what gives first, and at what torque figures it gives!

(would have been a good dissertation actually... dammit)

Share this post


Link to post
Share on other sites

Would that require milling the casting to take the bigger bearing?

What other improvements can be done? Oil cooler? There have been huge improvements in lubricants over the last few decades, I wonder, considering the bronze, what could be done with newer oils?

And could we seal the damn selector shafts?

G.

Share this post


Link to post
Share on other sites

There's no oil pump in the series gearbox to be able to use a cooler

Share this post


Link to post
Share on other sites

There's no oil pump in the series gearbox to be able to use a cooler

No pump, but plenty of gears meshing and moving oil. Can't take much to have a strategically mounted outlet in the casing.

Which is getting slightly away from the point - would improved lubrication help? Either in the chemistry, or location or temperature - I don't think the series box is particularly warm so it mightn't be an issue, but I'm trying to get ideas out there, so see what might work.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy