I have a '48 3.5 Mk IV with a ‘growling’ first gear. It is noisy on drive and less so on overrun. I need to remove and rebuild it sometime this year if all goes well with other priorities. I am concerned that the faces of the hardened tooth faces have no doubt delaminated and bits are being churned through the rest of the box. (As with these boxes, first gear is almost never needed, of course, but this won’t prevent contamination through the rest of the train.)
I am asking if anyone knows of the reason for this problem (if it is not uncommon, that is), and the bigger question is - what I should consider doing in addition to the usual works of replacing bearings, seals, and gaskets. New detent balls and springs?
I have a spare box which could be a donor if in good condition, but failing that, where can I get replacement internals for these boxes?
Hi Peter. Noisy 1st gear in a Moss box is standard, it would help for forum members to know where you are situated as that will determine the range of available spares/repair options open to you.
First gear in old transmissions often is a straight cut gear to reduce axial load, beneficial under application of high torque. Straight cut gears make lots of noise compared to helical cut. So, first gear noise is normal but increase in noise could be sign of trouble.
Early boxes 1st gear teeth weren’t hardened.
I think the days of finding a better box [ or engine, axle, diff wheels etc etc] left a few decades ago.
As Robin said , it depends where you are located. Here , we have a company that makes new 1st gears with a slightly higher ratio and rebuilds the gearboxes with them in it.
They have done all of mine and I’m very happy with the result.
The higherfirst gearmeans the car is not quite as efficient for pulling out tree stumps. But othewise slightly more use-able.
Thanks everyone. Just to clarify, this is not that gentle whine from a straight-cut gear, but is one that tells you it’s not in a happy condition and should not be used. I could not avoid using this gear on the last outing due to a mysterious dramatic loss of power which barely got me home. Still to be resolved.
I am located near Newcastle, about 150km north of Sydney but am not familiar with, or enquired about, any specialists that fiddle with this type of box. Saying that, there were thousands around covering the 20+ years Jags and other makes ran with them. I may have to resort to the replacement ratio set if I am not successful with the spare box but I would want to do the rebuild myself to keep costs down against my pension.
My other concern will be about the mechanical aspect with any new gears, as to the mismatch of the wear signature where one new gear (or cluster) mates with any remaining old worn gears. Obviously, to avoid this, I always thought all gears had to be replaced with new, or replaced with a mated full set from a donor box.
All comments appreciated.
(P.S. I’m doing some workouts to build up muscles for dragging the beast out of the bowels)
Gears { 1 st] as we are talking about should be replaced in pairs, But John Needham in Melbourne replaces them on both main and lay shaft. But generally the others are pretty good. Although i did once see a box where someone had replaced just one pair of gears, with double helical in a single helical box or vice versa, I’ve tried to erase it from my mind.
That being said i find nothing is cheap these days , and gearboxes are no exception. WE were talking early in the week about someone who had collected old Age use d car ads. Mk IVs for 100 pound, Xks a little more.
I remember a M IV abandoned in Arden St behind the Nth Melbourne footy ground.
Someone I vaguely knew had a Mk 4 as an everyday car. Went to aprty in it , a very good party apparently as he woke up in Sydney and couldn’t remember whee the party was , and so where the car was.
Yes, it would be ok to have a slightly more usable 1st gear. I have basically told my wife and daughter to avoid 1st in the MKV, especially since they are not used to the first-via-second when starting from a stoplight, nor the double-clutching or thinking much about the engine revs…
My gearbox was noisy when I first got my car but it was much improved when I replaced all the bearings. I know that the bearings are relevant to all the ratios (although less so with top gear) but slackness is a really big factor in generating noise. I have also experienced two rear axles, one in my SS and other in an MG SA where removing the slackness changed real grinders into quiet axles. http://www.nostalgiatech.co.uk/new_page_1.htm
Sawdust was another common noise reducer in the old days.
Ok seriously, it could be the front ball bearing, in which case a replacement is possible. Take off the top cover and post a picture of the inside. If it is a single helical, Mark V/VII XK120 parts may be the solution.
Bananas… sawdust… all sorts of stories abounded among the oldtimers when I was young and one wonders how many were true and how many other ‘additives’ were suggested…but I’ll stay with tradition and use oil. One characteristic to note is there is only the normal noise in reverse.
It will be a while before I can get to this part of the car as I am working on a list of items and struggling with recovering from a, hopefully short term, restricting leg problem.
One major task on the list is removal of all springs to have them reset. The springs are ‘new’, probably installed 20 years ago and the car hardly used since. The problem is they are over-cambered, sitting the car about 1.5"/2" higher, which means the rear axle is constantly thumping the chassis on the slightest ripple. There is no space to install bump stops and a prior owner strapped a bit of rubber insertion on with ties. They are ‘new’ because they do not bear any blemishes and after a bit of cleaning, the Lovells Springs stickers with part numbers were found still affixed. The number of leaves and their dimensions match other salvaged ones I have, so they appear to be the correct specification, but just too arched. Fascinating. The local spring man can fix.
It is normal for the rear springs to sit on the rebound stops. Actually in contact with them. If there is no rebound stop the axle will bang on the chassis.
This is not a very good photo but the axle is well and truly in contact with the stop.
Yes, the axle/spring relationship is such that the housing just skims the snubber, but with mine, the spring has been packed under the axle to gain some clearance and the car still needs to be loaded to get a snubber in place. The excessive downward camber with packer at the rear is also causing clearance problems at the tank/spare wheel cross member, and someone has had to angle grind a part of a spring strap for clearance. I won’t know the full situation until I remove them for unloaded measurement.
As a matter of interest, I couldn’t find a source for replacement buffers so made some myself. I used a standard Mackay buffer which was of similar footprint but twice the height. I had to add an extension to the plate to pick up the pair of holes and had to enlarge the initial holes but it looks good. With the pieces removed to halve the height, I epoxied these onto the original plates along with a few self tapping screws for reinforcement. From the two original buffers therefore, I gained two pairs of buffers. Ironically, since I did these several years ago, Simon Whitworth, UK, now stocks them and the cost difference is hardly worth the effort of otherwise turning this into a project.
This must have been the 1970’s??? Or earlier???
