stansoldman Posted September 5, 2011 Report Share Posted September 5, 2011 Ok Guys, the 7’s gearbox is making weird and wonderful tunes, When I purchased the car, I could hear a noise which disappeared when the clutch was depressed. First thought, thrust bearing. This was replaced but still has the same noise. I have been told it could be the main shaft.... Not up on lt77 gearboxes, so need a bit of advice on what to look for next. Thanks Quote Link to post Share on other sites
BizMan Posted September 7, 2011 Report Share Posted September 7, 2011 (edited) It may be a problem with the layshaft. Layshaft 'play' increases with higher mileage as a result of the poor design of the mounting of the input shaft to the front casing of the 'box (it utilises a tapered roller bearing that cannot be adjusted as it wears). The wearing of the bearing affects how the input shaft meshes with the layshaft and poor alignment causes the input shaft and layshaft teeth to wear. Unless the gearbox oil is changed frequently, the fibre teeth on the oil pump become worn by the swarf which reduces its ability to lubricate the 'box which in turn leads to further wear to the selectors, bearings and synchros. If it makes the noise in all but 4th then this is a clear indicator that it is the layshaft (as this is the only gear that goes 'straight through') in which case you will be able to strip the box and replace the worn tapered bearing. If the noise is in all forward gears then the wear has probably already gone too far and a full recon is almost certainly in order. The only way to know for sure is to strip the 'box and take a look. Edited September 7, 2011 by BizMan Quote Link to post Share on other sites
stansoldman Posted September 7, 2011 Author Report Share Posted September 7, 2011 Thank you for the advice, I would do the job myself , but having three slipped disc's, might prove a little doddgy. I have been quoted £645 for a replacement box with fitting..... how does that sound Quote Link to post Share on other sites
Alec Pringle Posted September 7, 2011 Report Share Posted September 7, 2011 That's not unreasonable, always assuming there's some form of warranty ! Ken Tomlinson, who built all the works competition LT77s and probably knew more about them than anyone else, used to recommend Motul 75W/90 gear oil and nothing else. The cheaper version is OK for road cars, or at modest extra cost the 300 fully synthetic. From my experience with rally V8 'boxes, I'd stick with that. Cheers, Alec Quote Link to post Share on other sites
BizMan Posted September 7, 2011 Report Share Posted September 7, 2011 I would speak to S&S Preparations first about supplying an R380- it is a stronger 'box and it doesn't have the design weakness that caused the problem in the first place. Quote Link to post Share on other sites
Odd Posted September 7, 2011 Report Share Posted September 7, 2011 (edited) My view exactly - why throw money on an (in essense unknown) 'rebuilt' LT77 when there are brand new, never molested/ misused/ rebuilt/ etc, R380 2wd gearboxes to be had OTC? For not much more money... It's a vastly better gearbox (with reverse to the right and down like most modern cars) - and you get a 0.77:1 fifth gear as a bonus... Only caveat is: be sure to have the gear lever extension shortened the correct way! Edited September 7, 2011 by Odd Quote Link to post Share on other sites
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