4 Speed Gearbox - Early vs Late difference?

[AHM]

Hi All,

I'm now starting work on the mechanical bits (which I find mored enjoyable than bodywork).

I have an early '69 S4 with a 4 speed gearbox. It does have the tag but not with me at the moment. As far as I can gather there is an early and late version of the box with the change in 1969.

My first question is how do I tell if I have the early or late box?

I believe the differences are in the Synchro hubs and baulk rings - Are all the other parts interchangeable?

Does anyone know what the detailed technical differences are? (I'm an interested engineer!)

I have searched the archive, I felt sure there would be someting on this subject but couldn't find it.

Thanks,

Simon

[paddy]

Any useful info in here:

elan-f15/rail-gearbox-t17826.html

?

Paddy

[garyeanderson]

Its been some time since I had all of the parts spread out on the counter but I found these baulk rings this morning and they tell you a lot about what you have. If no one has been messing with the box in the past then this should be mostly true. Baulk rings and baulk ring hubs are matched, early with early and late with late. You can swap matched pairs (hubs and rings) and they will work in late or early. Mostly the late boxes have a snap ring and the early have a draw nut. There are differences in the draw nut ones too so that is why I highly recomend the Dave Bean and other Ford manuals.

The baulk ring on the left is an early and the one on the right is from a snap ring (late) box. These hints will help until you get a Bean catalog

[AHM]

My gerabox has a nut on the mainshaft so i conclude it is the earlier type.

Paddy - Thanks... I should have searched for 3 rail gearbox - there are a few more threads.

Gary - Thanks again!

Of the four baulk rings I have there are 2 with a larger cone diameter and a pair with a smaller cone diameter presumably 1st/2nd and 3rd/4th (or the other way round)

Confusingly for the 2 with the larger cone dia. I have what looks at first glance like one of each in your picture - One identical to the one on the left with ford and S-R 07 cast into the face - And one with no markings looks like the one on the right with fewer teeth but no web in the blocker bar cutout and a shallower shoulder as the lefthand one.

The pair with the smaller cone diameter appear as described for the second one above - fewer teeth, no web, shallolwer shoulder. One has ford x-x 08 ? (a bit worn) the other is blank.

The previous owner wasn't shy about spending money so I'm guessing he used whatever was available at the time.... which doesn't look like it included 2nd gear!

I'll get the Dave Bean Catalogue as a source of future reference.

Simon

[Daholmes19]

Hi Simon

One trick to get the syncros to work to their maximum is to make sure the taper on the corresponding gear (onto which they grab) is not too shiny and polished, the action of the syncros is greatly reduced if the gear taper is too smooth.

There is a quick fix if needed, lap the gears with fine valve lapping compound until the finish is a dull grey across the service. Assuming you are fitting new brass syncro rings you can use the old ones to do the job, just coat the inside with the lapping paste and keep spinning them on the gear. Just make sure you completely clean all of the lapping compound off the gear before you reassemble the gearbox.

You can check the before and after with your new syncro rings, the lapping of the surface really helps the "bite" which is what slows or speeds the gear up or down before the syncro hub engages via the dog teeth.

Cheers
Dave

[AHM]

Thanks Dave. I'll give that a try.

I'm looking for that kind of solution. From what I have read the gear change should be a pleasure which has made mine all the more dissapointing so I'm keen to get it right.

I will probably need 2 or 3 new baulk rings and a 2nd gear which is making me consider new syncro hubs and hence my question. I'm trying to understand if the new type will give any improvement in gear change or if they are just stronger. The previous owner rebuilt the gearbox (10k miles ago) so apart from the second gear I would normally reuse everything but a terrible second and an indifferent 3rd gear change just give me a sinking feeling!

This also leads me to question how much wear is acceptable in the syncro hubs and blocker bars they don't look too bad, but I don't know what bad looks like.

I'd still be interested to knod the technical differences between the 2 types if anyone has a moment to reply.

Are there any other tips fore a perfect gearbox? I already have Redline MTL on my shopping list.

Simon

[Elan45]

The biggest point of wear I always see in these gearboxes is on the shift forks, especially the third forth fork on the 4th gear side. But bear in mind also that any wear on the fork will translate into a late engagement or an incomplete engagement and this is often seen when the box pops out of 4th or even grinds going into engagement. I think that some grinding going into intermediate gears can be the fault of worn forks at other interfaces.

Roger

[Daholmes19]

Hi Simon

I learn't most of this the hard way, my box was rebuilt along with the engine last winter, new bearings and syncros only though, if anything the shifting was worse than before, especially second gear from third. Made me feel even worse as the engine was rebuilt to QED 420 spec and pulls over 145bhp

Most of the parts are available but you have to hunt them down as soem are getting quite rare, I got a brand new OEM second gear, 3/4 syncro hub and layshaft along with some other parts from bearingkits. Parts are excellent as was the service;

http://www.bearingkits.co.uk/

I am also replacing both shifter forks, from Pat Thomas who is excellent, the gearbox should be out again in the next few days so it will be interesting to see the wear on the old parts.

Cheers
Dave
Woodstock, On
Canada

[Elan45]

Dave,

You may want to pay particular attention to the interlock plungers in the front end of the box. I'll bet your previous rebuilder left something out. There is a cross hole through the center shift rail and a small, like 3/16 or 5mm plunger lives in there. There are larger diameter plungers on either side, that are toggled in position by notches in the sides of the shift rails. All three plungers need to be there and operating smoothly.

Roger