![laycock overdrive adapter plate gt6 laycock overdrive adapter plate gt6](https://s1.manualzz.com/store/data/006427621_1-c7c0a8deb747959a092256b55d2b1706.png)
In effect it meant the action of the overdrive unit in 4th gear was absolutely instantaneous. If the propshaft is going round really fast when you fit a low ratio axle, the pump and the amount of oil it can debit per second is vastly increased.īeing as I used a 4.55:1 axle, this meant at peak power the prop was going round at 10 000rpm (scary I know). The action of the overdrive is very much influenced by the diff ratio. (x) ver), we dispensed with all the stuff like pump rattle and the pump shank was machined straight. The reason for this is, simply the darn thing is prone to pump rattle when cold.įor my competition unit of course (which of course I am very offended about being stolen - Mr Mike We. The later dashpot assembly is much more direct in action.įor those that are interested in really technical details, I happen to know the oil pump is machined with something like a 8 degree chamfer which influences its efficiency quite a bit. The small weak spring up the middle and the dashpot preload spring act together to make a residual pressure system which acts against the 4 really heavy springs on the sliding member and fills the pistons to, if I remember rightly,- about 1-2 bar. The early relief valve is preloaded and has tiny screw up the middle, which I have seen come undone and the whole lot explode internally. The early dashpot works on a different basis. In the competition unit built by Mr Britton at Layock I had for my Vitesse, (which was stolen by a guy in Sutton Coldfield), the operating pressure was raised to 680psi, and the oil ways drilled out.Įven Ernie at ODS didn't know what Mr Britton did, and there is no longer anyone around able to build an overdrive unit to this spec. The main high pressure mode is set by the strong small spring, which is itself tweaked by a few small shims which you can't see on this photo. This was a major improvement compared with all the older type OD units. The larger spring sets the idle/residual pressure so that the pistons remain constantly filled with low pressure oil.
#Laycock overdrive adapter plate gt6 series
Nowadays it's considered to be a "normal banal upgrade"Īs you can see, it's a somewhat simpler assembly and the dashpot is sealed with an O ring, rather than a series of grooves. The GT6 D type has a design fault, which is why they were a prime candidate to replace with my ground breaking J type conversion. I started doing overdrives well before ORS or OVD Spares even started,- servicing the rather weak GT6 D type units.Īt that time there was nobody doing them at all. Most people don't realise I have been building transmissions for these for so long. I have a small pile of overdrives to rebuild this month, mostly J type. This is the only photo of the SOLID ONE I can find. I have never understood any of the logic of any of that. The TR4 has a clutch well over engineered for 100bhp, while the TR5 which uses the same was always a marginal clutch cover, despite all the hype surrounding the Laycock units, (which are the same as used on the 2L Vitesse!) Otherwise why use the large clutch spline size common to the Stag/Jaguar Mk2/E type?
![laycock overdrive adapter plate gt6 laycock overdrive adapter plate gt6](https://www.picclickimg.com/d/l400/pict/302691643978_/Laycock-de-Normanville-A-Type-overdrive-Moss-gearbox.jpg)
In my view they should have had the larger Stag clutch on the TR5/early TR6 too, because they are always dying,. The main improvement in the Stag drive line was the clutch which used a 9.5" DS - (same as Jaguar XJS-6), instead of the smaller 81/2" used on the Dolomite and TR6. Only the TR4 and TR5 had the BIG accumulator which gives that whopping fierce activation you need for high torque. On the A type OD, by the time the Stag came along, they only had the small accumulator anyway, (as did the Jag Mk2s) so most of the stuff about the Stag being "high performance" is nonsense. Who knows why, because most of them fitted it from the factory! The solid dashpot is the part that does most of the improvement in behaviour of the operation of the J type.Īs in most overdrives this stuff is set with shims anyhow. Sprint has 6, like the Spitfire 1500 and Dolomite 1850. The number of starts is stamped on a lug on the end of the overdrive. To find the "starts" its exactly that, look down the hole and rotate the output shaft 1 complete turn and count how many times you see a "start" of a coiled tooth