Encom Posted December 16, 2015 Share Posted December 16, 2015 Now my gearbox / OD are almost, finally ready to put back together after spending months sourcing NOS parts etc. But one questions remain regarding the main shaft.1. What is the actual difference between a normal main shaft and a heavy duty one?2. How much of an issue is the tip of the main shaft, and what normally goes wrong?3. Keep the brass bush in the input shaft or fit a needle roller?4. Any disadvantages to having a needle roller over a bush?5. Mk1 gearbox with D type OD, is this bush and/or needle roller the same as the MK2 box ie: P/N: 144782?Help please! I really, really want to get my Vitesse back on the road. Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted December 16, 2015 Share Posted December 16, 2015 IIRC the standard tip size on the 3 rail gearboxes is 1/2" or approx 13mm. The single rail or "heavy duty" ones are more like 18mm.This issue is that the tips and tip bearings wear out relatively quickly as they are really too small for the job. This is worse on the bigger engined cars for obvious reasons.AFAIK standard fit was always roller bearings in that location though some do prefer PB bushes.I think the Mk1 2L and Mk2 are the same bearings wise. The were some changes to gear helix angles and synchro sizes at some point but not necessarily at the change of Mk.The larger mainshaft tip does definitely represent an improvement that will give longer service life. To use it you will also need to bore out the input shaft to take the larger roller bearing, or use a single rail input shaft (with fine spline) from a later Dolly 1850 or TR7 4 speed.Nick Quote Link to comment Share on other sites More sharing options...
RobPearce Posted December 17, 2015 Share Posted December 17, 2015 As Nick said, the standard mainshaft tip bearing is decidedly marginal for a 2-litre and they fail. When they go, the bits of broken needle roller fly around inside the selector hub and jam it into third or fourth gear so that you have to limp the rest of the way home with only that gear available. Which is tricky for hill starts. It's worse on overdrive boxes where there's only one proper bearing holding the mainshaft relative to the casing. Quote Link to comment Share on other sites More sharing options...
glang Posted December 17, 2015 Share Posted December 17, 2015 Rob as an aside, any idea how much extra noise, if any, a gearbox will make before this catastrophic failure, gulp! Quote Link to comment Share on other sites More sharing options...
GT6 M Posted December 17, 2015 Share Posted December 17, 2015 Not much, but if it goes, then ye will find gaan into 4 th frae 3 rd will crunch, an gaan frae 4 th to 3 rd will crunchas 2 shafts no lined up.if on an OD, then it will destroy the rear of that too, not v nice to see it after wards.Ive used a PB bush wid a scroll for oil to move about on a wornscored shaft re ground, the bush will give a bigger surface area to run on as compared to needles, as there a gap between the needles, there aint ona bush, and bush can be longer too, so moer surface area for a bearing surface.Biggest culprit for wear is lack of oil or,and infrequent oil changes. going up a hill, ona low oil level, esp wid an OD, then all oil will gaa into OD, leaving GB wid nee oil at alM Quote Link to comment Share on other sites More sharing options...
Richard B Posted December 17, 2015 Share Posted December 17, 2015 If you are rebuilding a box, I would say go H/D. Yes you need either an 1850 input (and clutch friction plate) or a rebored 3-rail input shaft. Quote Link to comment Share on other sites More sharing options...
glang Posted December 17, 2015 Share Posted December 17, 2015 hmmmm I think my gb will be coming out next year then. I dont like the idea of boring the input shaft as I imagine its only case hardened so you'd lose the roller bearing surface hardness. How many miles has your fb bush done now M? Quote Link to comment Share on other sites More sharing options...
Jonny-Jimbo Posted December 17, 2015 Share Posted December 17, 2015 Whilst that may be true, you could get it re-hardened. Quote Link to comment Share on other sites More sharing options...
glang Posted December 17, 2015 Share Posted December 17, 2015 Might be risky rehardening as you could adversely affect the rest of the input shaft including its drive gear. Dont know if it can be bored enough to take a closed needle bearing so not needing a rolling surface......... Quote Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 17, 2015 Share Posted December 17, 2015 Mick Papworth has the 18mm input shafts to suit the orig clutch after chasing the 1/2"shaft frequently giving up on the Vit6 I took my last rebuild up to MikeIts still going as far as I know , as I sold sold her for the 2000 saloonI have used a sleeve caged needle assy in a worn stem gear, but lubrication was then minimalit needed the oil holes copying fo the cage sleeve and this would have wrecked the needlescost effective but not reliablePete Quote Link to comment Share on other sites More sharing options...
glang Posted December 17, 2015 Share Posted December 17, 2015 ok thanks. I'll make me mind up when I get it apart..... Quote Link to comment Share on other sites More sharing options...
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