Morgan +8 Forum

Hi All,

I recently acquired a 1971 Plus 8, and one issue with it that I hope to address is that it is very difficult to shift into third gear, regardless of whether the car is running, driving down the road or stationary with the engine off. It goes into first very easily with the car stationary and engine either running or off -- so the clutch is releasing OK. It takes a deliberate tug of the gear lever to get into second or fourth, but it takes a lot of force on the gear lever to get into third.

Any ideas? I tried loosening the detents spring adjuster on the top cover, but that only seemed to make disengaging third easier.

I'm anticipating I may have to rebuild the 'box and reset the tension on the gear selector sleeve detents, but it seems like that would affect both third and fourth gear selection.

Steve

Is this a stock 4 Speed or an upgraded LT77 5 Speed?? Only reason I ask it that I had a 71 with an upgraded 5 Speed.

Cheers,
Mark

Hi Mark,

No it still has the original Moss gearbox. It has about 107,000 miles on it.

Steve

Steve, sorry I should have picked that up from the title of your post. My bad.

I am not a Moss Box expert, perhaps there are others out there that can help.

I recently pulled an old Moss box (1938) out of one of my cars and sent it to Billy Bellinger in the UK. (https://jb-engineering.co.uk/)

I might call him and ask your question. From what I could ascertain over several phone calls he is very knowledgeable and seems to be free with advice. I would say he seems to be challenged by email, so I would strongly suggest you call. The number in on the website.

I have heard of places in the US that service these things but have no direct experience. Given the age of my box, I went back the UK.

Cheers,
Mark

Have you changed the gearbox oil yet? Some owners might run a heavier oil to reduce leakage, which may increase shifting effort. I currently use a Redline 75W90 "non slip" lubricant, which adds some authority to the synchros. This increased effort shifting into 3rd, improving shifting.
Before removing the gearbox for a rebuild, try changing the gearbox lubricant. There are a few different Redline lubricants that work. Others here can tell what they are using to improve shifting.

Mark and Jan,

I just got some Redline MTL-90 to try -- it will be interesting to see if it makes a difference. My question about third gear is partly academic; I'm curious about what would cause one particular gear to take a lot of force to engage regardless of whether the car is moving or not and whether the engine is running or not.

I too have seen many references to Billy Bellinger's expertise, and will likely consult with him. I imagine shipping a Moss box back and forth from US to UK would be pricey, so I would hope to narrow the issue down to specific parts that could be replaced or repaired.

If I do get into a gearbox rebuild, I may temporarily swap in another high ratio box out of my Plus 4 project car.

Steve

There are a number of US Moss experts. The gearbox was also used in Jaguars, so the technology is still available in the US. I would contact Morgan Spars for a gearbox rebuild, or do a quick internet search. I rebuilt one in College, about 50 years ago. Not really complex.

Greetings Fred's book has a very complete write-up on rebuilding the Moss box. I've been looking at it because the original box in my car has a chipped first gear and the spare I've had laying around for some time doesn't seem to be quite right either. Hopefully I can build a good one from the two. I also have a Jag Moss box with overdrive that looks great but they don't fit well in the two seater.

Tim

Fred Sisson's Morgan guide gives pretty good, detailed information about going through the Moss box and specifically addresses spring tension in the synchro hubs. If the box is not particularly noisy or illustrating other problems, it may be that looking at the spring tension in the hubs would be helpful. Unfortunately, as you know this requires disassembly of the box, but depending upon your confidence level could be something you might consider yourself. Have you driven another Moss box equipped car as a comparison, just curious as some do exhibit more stiffness in operation than others.

Hi Steve,

I have not seen this particular problem before. I know that early Jag Moss gearboxes could get stuck in 1st gear (later gearboxes have a fix for this). I've had my Plus 8's Moss box get stuck in 3rd gear occasionally and had a different Moss box get stuck in 4th gear. I've also seen a problem with reverse gear (knocking against other gears during deceleration) that was fixed by using a proper thick gasket for the top cover. Because of encountering these problems, I've had occasion to disassemble at least four Moss gearboxes and have completely rebuilt two of them to the Moss manual's specifications.

Since you have a spare Plus 4 gearbox, you might try this experiment before removing your Plus 8 gearbox from the car: remove the transmission tunnel cover and then remove the top lid of the Plus 8 gearbox and see if it will go into third gear without being attached to the gearbox. If it works OK on the bench, replace it with the one from the Plus 4 gearbox and try shifting into 3rd gear. If it still won't go into 3rd gear, you'll know it's a problem in the gearbox itself. If it works properly when using the Plus 4 gearbox lid, try the Plus 8 top cover on the Plus 4 gearbox to see if you now can't select 3rd gear in that gearbox -- if you can't, that points to a problem with the shift mechanism, either where the lever fits into the rails or perhaps with something bent inside.

If the problem is with the gearbox internals and you decide to use the Plus 4 gearbox, swap its top cover from the one from your Plus 8 so you have a reverse light switch (Plus 4 covers don't have one, at least not the early ones).

If you decide to rebuild the gearbox, you'll find it a pretty straightforward job, particularly if you have a copy of the Morgan Bedside Reader. You'll also want the Jaguar repair manual, which includes some important specs not mentioned in Fred Sisson's collected how-to articles in the Bedside Reader. I can send you a pdf of that.

Stephen mentions the detent balls and springs and that seems a reasonable assumption, although can't quite connect the dots. Typically, less spring force on the synchro balls makes it easier to shift into a gear but reduces synchronizing action, so it's easier to crunch the gears when shifting. Greater spring force makes the shift action feel very notchy but makes the synchros more effective. I suppose debris could find its way into the synchro hub, keeping one or more balls pushed outward with no ability to be forced inboard against the springs. That would make the hub impossible to move -- however, that should theoretically also make it impossible to put the lever into 4th gear as well, since 3 and 4 share the same hub.

Therefore I tend to think it may be a problem with the shift fork or perhaps in the raised "tower" where the shift lever passes through the top of the gearbox cover. Perhaps the lever itself is blocked internally.

Duncan

All good information Duncan.
Some years ago, I was involved in a Morgan restoration and the gearbox and engine were done by another fellow who was a pretty good mechanic. I believe he may have increased the spring tension on the synchro hubs by replacing the springs or in some other way. I found that shifting gears in this Moss box took quite a bit of effort and remember it to this day. This sort of comes to mind in this situation.

The first time I rebuilt a Moss box I put two thin washers (5/16", perhaps, same diameter as the balls, or slightly less) under the springs and ended up with a notchy shift feel. For some reason that gearbox had to come out again before too long and I removed one washer from each hole. It's easy to test the tension by using a drill press and a calibrated bathroom scale. I was within spec both times but the high lbs. figure seemed excessive.

Duncan