Beginners guide to Morris Minor gearboxes

1 36 Minor Monthly May 2009 INTRODUCTIONF irstly, let me explain how I entered into the world of gearbox-es . I have owned and run Morris Minors for about 15 years, cur-rently using two white convertibles for wedding hire. As weddinghire is largely seasonal, I was looking to generate income in thewinter months. I had about a dozen gearboxes of unknown ori-gin and originally considered rebuilding them to sell trained as an engineering apprentice I had no specif-ic transmission rebuild experience. The problem with gearboxrebuilds is that there are so many parts! Most people find themscary and one silly mistake can result in an awful amount ofextra work, not only to rebuild the unit, but also in refitting it to thevehicle. I have even considered building a test rig to test boxesbefore sale, but it is very difficult to replicate driving conditions,particularly in the area of the synchromesh. Time-served trans-mission builders will be wondering at this point what all the fuss isabout, but as is usually the case with many trades, they learn byrepeating the process time and time again, until it becomessecond nature.

2 This experience is, of course, not available to theaveragely competent home mechanic. New original parts arehard to come by, new parts are not being remanufactured dueto tooling and setting-up costs; second-hand boxes are nowover 35 years old and of unknown serviceability. Many of our fel-low enthusiasts overseas have rust-free cars, but are wearing outtheir transmissions. I reasoned that it would be easier to postthem a couple of gears, than a complete gearbox! So I decid-ed to strip my gearboxes and sell the parts. What follows is thestory of my journey , hopefully passing on to you what this layperson learnt on the are three basic types of gearbox fitted to a Morris Minor ,excluding the side-valve, which is completely different. The twoearly variants known as smooth case fit the 803 and 948ccengined cars. The 948cc has a remote gear change similarto that of the later 1098cc ribbed case type and in manyrespects is interchangeable with this later gearbox, with somemodification.

3 Beginners guide to Morris Minor gearboxesAndrew Bywater guides you through some of the pitfalls of replacing or repairing the A series in-line ribbed case gearbox can be fitted to the earlier cars,but you may encounter issues with gear ratios, poor accel-eration, clutch clearance, gearbox front cover and clutchrelease arm etc. Conversely, if desperate, a 948cc smoothcase box can be fitted to a 1098cc engine, not really recom-mended, as you are putting more power through a weaker boxas well as dealing with far more problems in the area of theclutch. There are several articles covering these issues in variouspopular modification manuals, which go into this in more detail. They use the same gearbox floor cover; the gear lever isin the same place. The early 803cc Morris Minor smooth case box is similar to that of the Austin A30, but beware, as there is a trap , one, which I once fell into. All three types of Morris Minorgearbox are the same length (26?)

4 Inches approx.). The 803ccMinor box achieves this consistent length by having a longertail casting unique to the Minor 803cc car, meaning that thesame propshaft is used but a different floor cover, as the magic wand gearlever is longer, emerging from a differentplace in the floor. The Austin gearbox is about 4 shorter, usinga different tail casting, so be careful! The 1098cc ribbed case gearbox is the later variant fittedfrom about 1962/63 until the end of production. It is stronger p36-38 25/3/09 11:39 Page 2 May 2009 Minor Monthly37 Workshopthan the smooth case boxes that preceded it. One majoradvantage is in the synchromesh. 803 and 948cc gearboxesemploy a cone-type synchromesh, identified by a gold coloured band on the gearwheel whereas the 1098cc boxemploys a separate baulk ring. The 803 and 948cc new oldstock gears normally come with the gold cone fitted, but it isshown in the parts book as a separate item, although to fit thiscone in practice requires the services of a machine summarise,things are easier forthe Minor owner thanthat of the Austin.

5 Thegearboxes are all thesame length, as arethe propshafts. Austin948 and 1098 gear-boxes can be fitted tothe Minor just by swap-ping the clutchrelease arms andignoring the threadedholes in the bell hous-ing casting as theAustin s hydraulicclutch slave cylinderwould bolt to these,the Minor system is mechani-cal using a release arm with ahole in the end rather than IT A GOOD ONE?As they say, the 64,000-dollar question! Proudly cradling this oily 50 lump in your arms bought off e-bay, is this baby going tosave you the 400 extra that a fully reconditioned, guaranteedunit would have cost? If you re lucky, you re in the poundseats , if not, you re 50 down and spent the weekend lyingunder the car for nothing. That s the gamble you take; here area few pointers to minimise the risk:Insert the gear lever, and select all of the gears while turningthe input shaft. Does it turn easily, and does the output shaft turnas well (opposite way for reverse).

6 Grab the shafts both endsand jiggle them. Is there much play? There will be some, butunless you have several gearboxes it is difficult to judge goodfrom bad bearing play. One consequence of front bearing playis wear in the scroll-type oil seal in the front cover caused byexcessive ex-centric movement in the input shaft. If this is left, oilwill be lost, contaminating the clutch and the resulting lack oflubricant will limit the service-life of the gearbox. A modifiedfront gearbox cover incorporating a lip-type oil seal and carrieris available from parts suppliers as an Owen Burton mod. At the side cover off the gearbox will expose most of the innards for inspection, but be careful not to trap or lose the twoplunger springs that will be released. You will be looking for any-thing obviously awry, broken, chipped or rusty (milky) oil indicating moisture or even water, which willhave done the bearings and shafts no good at all!

7 Having bought many second-hand gearboxes , one popu-lar statement I ve heard is she was a good-un when she cameout of a car I scrapped . The seller genuinely believes that theyare selling you a really great unit, and price it accordingly. Theyforget to mention that this was 10 years ago, that it has beenstored in a damp garage, stood on it s bell housing, draining allof the protective oil down the 1stmotion shaft! As a conse-quence, once fitted the gearbox bearings howl like a bansheeuntil ther e s u l t i n gbearingplay causesprematuregear failureAnotherclassic is she s agenuineBMC gold(or silver)rebuilt unitmate . This p36-38 25/3/09 11:39 Page 338 Minor Monthly May 2009usually means that the box has been reconditioned sometimein the last 50 years, and that it has done 80,000 miles since therebuild! It turns out that this gearbox is worse than the one thatyou have just taken out! I have even known unscrupulous peo-ple set to a dodgy box with a gold or silver aerosol can of paintand some BMC transfers!

8 The best bet for buying a second-hand gearbox to fit as is is to obtain one from a recently scrapped car where it has lainin the frame horizontally full of have sold gearboxes of unknown origin that haveappeared to be OK on the bench, and most have worked. Igenerally sell these on a 90-day money-back guarantee, thebuyer s risk is his fitting time or garage charge, however the sav-ings with this gamble can be considerable, particularly for asummer Sunday afternoon hobby YOUR OWN GEARBOX!There is no reason why a reasonably competent homemechanic armed with a manual, a basic toolkit and plenty ofpatience, working in a methodical manner cannot rebuild theirown gearbox. I shall not go into great detail here as the subjecthas been covered many times before. Practical Classics mag-azine ran a very good 3-part article on the subject in the springand summer of 2008 the back-issues should be still , I shall offer a few pointers and observations based onmy experience of stripping scores of Morris Minor time you rebuild a gearbox there are certain parts thatyou will always need, as follows: Gaskets.

9 You can make your own, but are almost cheaperto buy from the popular specialists. Tail seal. Always worthchanging for what they cost, and it saves a mess on the garagefloor! Bearings can be obtained from Minor suppliers or fromyour local bearing specialist. Beware of bearing supplier priceshowever, as they use astronomical retail prices sometimes dis-counted by 80% to the trade. Find a friend with a tradeaccount. 803 and 948 smoothcase boxes use the same mainbearings front and rear, which is thesame as the front one on the1098cc, ribbed case gearbox. The1098 rear bearing is a different thick-ness . You will also need a pair oflayshaft bearings and a smaller nee-dle roller bearing for the 3rdmotion(mainshaft) spigot. This is a brassbush for the smooth case are a number of transmission specialists who advertisein the classic car press or on the Internet who supplybearing/seal and gasket kits for about 75 + VAT & in my experience virtually all show signs of break-up ofthe case hardened surface.

10 I have only found 1 or 2 to be re-usable in the scores of boxes I have dismantled. Be carefulwhen buying replacements, as quality is variable, and new oldstock is virtually only otherpart that you maywish to considerprior to startingyour overhaul is the1st/2ndgear syn-chroniser hub. Thisis the bit that goes crunch when youengage 1stgearon the move. Thiswill have some wear but may be re-usable in 75% of ! When handling this gear, be careful not to acci-dentally push the 1stgear ring off the central hub. There are 3spring-loaded ball bearings ready to launch into outer space ifthe gear ring is allowed to slide too far. I have been able to re-assemble these using a Bisto jar lid, a jubilee clip and a lot ofblue language as well as a large supply of balls and springs! p36-38 25/3/09 11:39 Page 4 The previously mentioned synchroniser springs can becomeweak/crushed or distorted by the habit of parking the vehicle in1st gear.