deja vu

Following the sound proofing effort and oil change/service, I took the 109 on its 265 mile trip to work.  The car was astonishingly quiet, eerily so, in fact, quieter than the 90XS.  The sound proofing really works better than I could have hoped for, leaving only road and wind noise to be significant.  However, the new transmission oil (75W90 semi-synthetic) seems to have been no good.  By the time I got to Luton, all gears except 4th were howling, sounding similar to reverse.  Fourth remained quiet, so it is seemingly a lay shaft issue in the main gear box.  A second oil change with fresh EP90 when I got home has not rectified it, so the box has to come out yet again for inspection and repair, even though it is operating correctly and no bits came out with the oil.  I suspect it is just the lay shaft bearings, but I will be replacing all of the gear box bearings.  So, never use anything other tan EP90 GL4 or 5, folks!

While I am at it, I am dropping the 3.54 diffs and refitting 4.71 original ratio SIII diffs to the modified axles.  Apart from being a nicer, if noisier and slightly thirstier drive, I am fed up with rebuilding this transmission.  It ran for years with the overdrive, Tdi and standard diff ratios without missing a beat, so I hope that this will be the last repair on it for some time.  The speedo has been removed for recalibration back to standard by JDO Instruments as he did a very good job last time.  SO, the 3.54 diffs have been an expensive and very negative experience for me, despite the 10% fuel saving they delivered.  I suspect this latest issue is more to do with the oil than the diffs, but I’m sure they’re a contributing factor – as far as I know, SIIs and SIIIs in large parts of the world are run on 75W90 because EP90 is not available there, and I don’t hear of them having much problem.

Be Sociable, Share!


  1. Fantastic news on the soundproofing, great job! 🙂

    I’m still not sure how we found no difference with the WOR matting while you found it worked well but I can only guess at our truck cab body style being the main cause of the difference with its lack of interior trim. The WOR matting in your case working in conjunction with other interior trim? I also wonder if having the fabric defender seats reduces noise over running the vinal series slabs which we have. I would have thought the more soft furnishings you have the less noisy it will be?

    Sorry to hear about your gearbox woes. It does support my findings when running 3.5’s and having similar gearbox issues shortly afterwards. You and I do comparatively high annual mileages in our LR’s so the problem shows itself much earlier than people that only do very low mileages. The first thing I ask people now when discussing the supposed benefits of a modification is how many miles they’ve done on it. It always makes me smile when somebody claims that they’ve run with such and such a modification for years without issue only to then find they to just 1K a year in mileage – 1/20th of my annual mileage! 🙂

  2. Thanks Ian.

    I know exactly what you mean about internet advice. Generally, I find that the more insistent someone is about their modification, the worse an idea it is. There are some very gifted and talented DIY mechanics and enthusiasts out there, but there are also a lot who really shouldn’t be allowed to open a tool box under any circumstances! The good guys tend to back up their views with detail on how they did something and what the consequences, good and bad, were. I try to do the same, which is why I’m open about the continuing disaster these diffs have been for me. Someone else I know has them on his vehicle with a standard transmission and a V8 and has had no problems apart from an occasion of “spirited driving”, but his vehicle is very different in application and most characteristics to mine, so his experience will be quite different too. Tdis might not have as much torque as a V8, but the delivery is harsher and my 109 is hard to push along with all that drag and weight.

    I think the key to noise issue is to have a complete approach. At the end of the rebuild, I still had bare interiors on the hard top sides. I got a lot of drumming from the side panels behind the sliding windows, and adding the self adhesive material from Noise Killer made a huge difference to the overall noise, even though they were only a small area of the interior. I was disappointed by the apparent lack of effect their matting had on the engine bay, given noise levels before the rebuild seemed similar, but with the cab floor, tunnel and seat base omitted, perhaps I was being unfair. This cheap foam from Dunelm Mill,which would be no different from that sold in any DIY or haberdashery shop, seems to do a wonderful job, but that might be just because I have stopped the noise that was coming around the previous protection rather than through it. Think of your matting kit like the Maginot line – it can’t hold of invasion if the enemy can walk around each end!

    I suspect that fabric seats may have a small benefit over vinyl. I’m sure if I had a soft roof lining rather than the hard LaSalle one and foam and fabric covered side panels instead of ply and vinyl at the back of the sides, I’d get a lot more noise reduction, and using carpet with foam or felt backing in place (or better, in addition to) the current floor matting would make a hell of a difference. It really is a case of every little bit adding up. Any bare metal panel is going to transmit a lot of noise and render the matting kit ineffective.

  3. Cameron Wood says:

    I have recently reverted back to running 75W/90 semi-synthetic gear oil in both gearbox and transfer box and it is an improvement over 90EP in my experience. I did run 90EP for quite a while in two different gearboxes and I did run 75W/90 in my old gearbox and in both cases, the 75W/90 made it quieter, easier to change gear and the oil stayed in good condition, for longer in my old gearbox. I have yet to see what it is like in this gearbox, being an earlier suffix-A over my previous suffix-D.

    However, I do know someone who has used 75W/90 semi-synthetic oil for a very long time (around 10 years) in a Series III gearbox without problem, and that thing does thousands of miles per year, using either a 200Tdi with a Td5 intercooler, high flow air filter and straight through exhaust. I have also heard similar stories to your own though, and whilst it is currently working for me, I am wary of recommending it. If it’s fine in two years’ time after a couple of changes, then yes I will say it’s fine.

    Talking of oils, I think the old 2.25 engines in good order will happily take 15W/40 semi-synthetic and retain adequate oil pressure. I found an increase of 5psi at 30mph with a hot engine compared to 20W/50, but it dropped significantly on 15W/40 mineral. Therefore, I now only recommend using 20W/50 mineral or 15W/40 semi-synthetic from a proprietary manufacturer to other owners (proprietary meaning Castrol, Mobil etc.), but as I said, this is my opinion. The semi-synthetic also was remarkably clean after a second change, and the first cleared a lot of sludge.

    Regarding sound insulation, I have a lot of acoustic foil-backed open-cell foam behind the roof lining, under the floor, seat box, and I did have it in the doors. I also have an Exmoor Trim acoustic carpet set front and rear. I did have some hessian insulation under the bonnet and I can attest that even though it didn’t cause my fire, it certainly fueled it!

    My advice to owners now is ‘do you really need to modify it mechanically’? Whilst I have seen some good, well-thought-out modifications and conversions (a Series III 88″ on the BLRG stand really stands out for me, well I am a club member in an 88″ SW after all!), many have been complete bodge jobs and really badly done. Therefore, I say, unless you need it and can perform the conversion to a high standard, leave well alone and buy something you really need, or trust the job to someone who does know what they’re doing. There’s too many vehicles with badly carried out repairs and conversions, using suspect parts or are in plain poor condition, and in my opinion, shouldn’t really be on the road.

Speak Your Mind


By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.