Three Litre gearboxes

I cannot help but feel that the excellent work being done by PRO Rob Rowe is rather being undermined by the information on the main website about engines and gearboxes saying: "TD 21 onwards, it is not such a happy story. The BMC 4-speed box, OK in Austin-Healeys, is not up to the torque of the Alvis engine and can break. It also has a poor change, weak synchromesh on second and peculiar ratio spacings. First is high, second is hardly any higher, yet there is a monster gap to third, which is very close to top. Since, however, it is used in the Austin-Healey 3000, parts can be had.  "Not so the pleasant to use but woefully fragile ZF 5 speed unit. It has a slick change and excellent ratios, but inside it is watchmaker's stuff and it is prone to whine in the indirects when even slightly worn. Parts are in the hen's teeth category for availability. A remedy is fitting a Getrag box from a modern BMW, this can be very expensive... The most satisfactory gearbox for the later Three Litres is the ubiquitous Borg Warner automatic: robust, easy to fix, parts plentiful and cheap."  It surely behoves the Club to work with owners who would like to fit a modern gearbox to overcome the ZF problems and with Red Triangle to come up with a cost-effective but elegant solution. The S5-17 box in my TE21 offers a streamlined transmission tunnel. Park Ward overcame the problem of the short lever on top of the selection mechanism in TFs with the S 5-20 ZF box by designing a nicely trimmed "oddments tray".  Perhaps if 10 owners would commit to spending, say, £5k each on an upgraded gearbox fitted, that might allow RT 10 x £500 = £5000 to do the necessary development work. The ZF box in my TE21 is certainly noisy on 1st, 2nd and 3rd which detracts from the driving experience. Posted by vaningen 20/12/2013 23:06:14

Just a passing thought; is it possible to fit an original Alvis box from the TA-TC 108/G series?  I am aware that by the late 50's they had reached their "use by" date in terms of quietness, hence the decision to fit the BN4, however they are regarded as virtually bullet proof. Perhaps Chris Prince could offer a comment? Posted by RichardWallach 22/12/2013 21:01:10

I think you are mistaking the TA-TC gearbox for the prewar synchro box Richard.  The TA-TC box certainly isn't bullet-proof, but because of that, there are at least plenty of spare ones around that have been removed from cars because there is something wrong with them.  They aren't unduly complicated to rebuild. Posted by Angus D'Arcy-Drake 23/12/2013 09:13:21

I do not understand some of this discussion. Surely the ratios of all the manual gearboxes are not greatly different.  In my experience, Healey spares would be of limited value. Many years ago now, I dismantled a Healey and TD21 box side by side, externally they were identical apart from the gear lever mechanism, but the internals were different to the point of the gear helicals being the opposite way round!  My TD21 Special has a Ford type 9  5 speed box as fitted to the early Granada, slick change and quiet. these are still available, I think, though maybe not at £70! there is at least three choices of ratios but the may not be strong enough for TE/TF?  The weak point I understand is the layshaft bearings, so I have a standby box fitted with larger ones. Other boxes can be used, but none are straightforward spanner job to fit. Posted by jackclover 23/12/2013 15:34:58

I agree that the new gearbox description does sound rather pessimistic. When I bought my TD21 series 1 in 1974, it had just been fitted with one of the very last brand new gearbox and overdrives available. I had many years of very pleasant motoring and didn't notice that the gearbox had any problems. However, I always started in 2nd gear (except on a very steep hill), a habit learnt on my Father's 20/25 Rolls Royce. I have always driven my TA14 Carbodies drophead in the same way.  My TE21 is a very different animal. I acquired it in 2001 and immediately found that driving in the West Country was a major challenge. North Devon in particular has very steep hilly twisty roads. The synchromesh seemed very weak and the gearbox kept jumping out of gear. It was also very noisy. This, coupled with the fact that the handbrake wasn't capable of holding the car on a steep hill (even with constant adjustment), made me realise that something had to be done. I remember one nightmarish stay in St Ives. The constant hill starts on very steep inclines were extremely stressful.  The solution 12 years ago was to have a 4 speed ZF automatic gearbox fitted by Graham Whitehouse in Birmingham. Sacrilege some may say, but the driving experience is so greatly enhanced that the car has been a real pleasure to drive since then. I can also park on a steep hill without worry and do hill starts. I would be interested to hear how a brand new ZF 5 speed box would perform for my situation. My conclusion was that a worn gearbox really detracts from a pleasant driving experience: great if you don't use the car very often, but no fun if the car is to be used seriously. As my car is high mileage (160,000), I don't feel too guilty!  David. Posted by DavidMJS 26/12/2013 16:40:50

I explored the Whitehouse option about a year ago but as the quote was over £8k + VAT, I decided to go no further. Posted by vaningen 28/12/2013 19:29:23

I think my decision was rather influenced at the time by the fact that there were no options for rebuilding the ZF 5 speed box. All the available solutions cost about the same, so I opted for the ZF 4 speed automatic box. I upgraded from my TD to the TE for the power steering: the option of having an automatic as well suited my increasingly geriatric state! I have to confess to another terrible admission, I have the Jaguar "J" gate gear selector as well. Posted by DavidMJS 29/12/2013 12:28:21

I notice that on Chris Prince's "online parts shop" website there is a 5 speed gearbox conversion listed for the TD21. Posted by drdowhitt 30/12/2013 06:17:05

CHRIS PRINCE REPLIES:  The solution is already here. I looked into the options a few years ago as there was clearly a market for a five speed box. The Austin Healey based box is not the nicest of units even with overdrive, and yes the parts are available, a full rebuild is not cheap and does not improve the ratios. Fitting an overdrive to the four speed may give you a higher top ratio, but if the gearbox has weak synchro or worn internals, it does nothing to address those issues. The ZF box is OK when in good condition, but parts are expensive if available and finding a box to do a conversion was becoming almost impossible. The shortlist for a modern replacement included the Getrag, the Ford type 9 and the Toyota Supra, but soon I settled on the Tremac T5. It is still in production, which means a brand new guaranteed unit with no parts supply problems. Fitted to TVR's and Mustangs it will take the power of a three litre twice over. Physically it fits, and the ratios are very similar to the ZF with 1:1 fourth and 0.8:1 fifth.  The basic kit to install the unit in a manual TD comprises gearbox, adaptor plate (the conversion uses the existing four speed bellhousing), mountings, propshaft, clutch driven plate, gearstick and a few other bits. Some creativity is needed with the hole in the transmission tunnel and carpet,  as the lever is slightly further forward, but otherwise the job is straightforward. The cost of that kit is currently £4012 plus vat. For an auto to manual conversion, additional items such as clutch, flywheel, engine backplate, bellhousing, pedals and transmission tunnel are also needed, all of which I can supply, and similarly for a ZF conversion, bellhousing and other bits are needed. I can confirm that the conversion works very well and makes the car a pleasure to drive, the options are somewhat limited in any case, there are very few cars now produced with a rear wheel drive set up, so inevitably the choice of possible units is restricted.  As one of the few suppliers of parts for the Post war Alvis I am very much in tune with owners requirements and wishes. I am currently working on an installation kit for an electric water pump using a modified lower water elbow. This I hope will be available from stock by Easter, in time for the red hot summer ahead. Posted by chris 30/12/2013 10:51:00

Having spent one evening with the (then) Lagonda spares secretary and a micrometer, measuring a batch a gear wheels manufactured for the Lagonda club, I wonder whether it might be possible to get some of the internal parts for the ZF box(es) manufactured in small numbers by a specialist.  As the 'box is German the bearings will be metric and should therefore be readily available, gears and shafts can be cut, etc.  I know that small batch manufactguring is expensive, but it would keep the cars original, and the ZF box performs well when in good order, or at least mine does, and it has covered about 80,000 miles. The ratios are well spaced, it is smooth and quiet except from the 'click' of the steel detent balls when changing gear.  I have had the good fortune to obtain a spare ZF box (NOT for sale, before anyone asks), which I would be prepared to use to obtain dimensions for internal parts if anyone thinks it would be worthwhile to pursue the suggested route. Posted by greg124 05/02/2014 20:29:17