4 speed gearbox overhaul

[martinbrowning]

Hi there!
I currently have the 4 speed box from my S130 on the bench for overhaul.Two questions please:

a. it is quite difficult to engage 3rd or 4th-is that indicative of a worn synchro assembly?(1st/2nd and reverse engage really nicely).

b. I intend to replace the three bearings in the mainshaft/extension shaft train. Is there anything else that I should do whilst the box is on the bench?

Kind regards and happy Easter!

Martin B

[alexblack13]

Hi Martin,

Yes! Could well be.
Also...

Replace OR at least carefully check the needle roller bearings on the lay-shaft along with the thrust washers. Check for worn balk rings and selector forks. Renew all oil seals.

Sounds like you are on top of it.... It will give many years of service when rebuilt correctly..

Good luck with it..

Do you have a 'dummy' lay-shaft / pin? Used to keep everything in place when removing and replacing the lay-shaft? Its a pig to do it without one!.. I can loan you one if you need it...

Alex B....

[elangtv2000]

Hi Martin,
Supporting what Alex has already told you, adding an additional two cents (yes, I'm in the US). I've rebuilt 4 and torn down 6 of these 'boxes, and am putting on a gearbox session for our local British car club on May 1 - come on out to California and join us
In addition to worn synchros, worn layshaft, layshaft bearings, worn slider rings, and particularly, a worn shift fork can cause difficult shifting. The 3/4 shift fork wears prematurely in many of these 'boxes, I think in part because many drivers rest their hand on the lever while driving, and also because in Elans, the shift boot can pull back slightly on the lever when engaged in 3rd gear. I've seen a couple of 'boxes out of Cortinas that also had severely worn 3/4 shift forks, and suspect the lazy hand as the primary cause.
A worn layshaft and/or bearings will usually be accompanied with at least some excessive noise, but excessive play can make sometimes make shifting difficult. Worn synchros will usually be obvious by the clashing, more so than it just being difficult to push the lever.
Diagnostics aside, my view is to replace every bearing and synchro, the layshaft (not always needed), needle bearings, and thrust washers - both the small stainless ones that retain the needle bearings in the laygear, and the bronze dimpled washers in the case that the ends of the laygear bear against. Don't forget to assemble with oil. The parts are not that expensive, and it's much better to know you're not likely to have to go through this exercise again for a long time. I keep spares from several 'boxes to use in others, such as sliders, forward gears, and reverse gears (those get badly bunged up in use). A dummy shaft will save lots of time and effort, and can be made by cutting down an unserviceable layshaft, or by making one of aluminum or even wood - it just needs to be the length of the laygear, and slide easily in and out.
As Alex said, a properly built and uses gearbox will give many years of service, and they shift like few others - a real treat.
Cheers,
Greg Tatarian
1971 Elan S4 DHC

[66S2]

Greg:

When/where is your gearbox tech session? Looks like you are a GGLC member but I don't see your session on their calendar. Thanks.

[elangtv2000]

Hi,
The session is actually for the NOBBC, but GGLC members are welcome to come. I didn't post it on the GGLC calendar because I'm going to host another for that club later in the year. I'll also be hosting another Lotus drive, hopefully again with John Kenner - did you make the October 10 event?
May 1 will be a fairly brief tech session (2 hours), plus a BBQ social gathering at my house. If you'd like more info, PM me or email [email protected].
Cheers,
Greg

[martinbrowning]

Alex,Greg,

Many thanks for your helpful guidance on the gearbox rebuild-you have confirmed my instinct which tells me to do a complete overhaul/rebuild whilst it is on the bench.

Mind you,the current curent job started as a simple "check for hesitancy" and has continued into a "whilst I'm at it...." Engine and gearbox on the bench and body away in England for respray. (I was lucky enough to have a new silver windscreen trim).

Alex-would appreciate the loan of the dummy shaft.PM on it's way.

Regards

Martin B

[alexblack13]

Ok got it and replied.. Shaft on way soon..Homemade but works fine!

AB.........