Lotus 5 speed: Trouble engaging 4th

[mbell]

Hi,

My car has the Lotus 5 speed box in it with unknown history, apart from a recent oil change to Redline MTL. The box doesn't want to engage 4th gear, all other gears seem fine (haven't drive it fast enough to use 5th yet but seems to engage correctly).

When trying to select 4th you can feel it operate the sychro but it doesn't fully engage the gears (grinds when driving). The stick springs back to "half" way into forth. Testing by rocking the car (engine off) you can get it to engage 4th by holding the gear stick fully down in position for 4th but is jumps halfway out when pressure is release and the gear partially dis-engages.

I tightened the stick mount to the box (~1/4 turn) with no improvement. The stick looks ok and the rubber spring/bush things seems in decent condition with out any extra spacers added. The metal tabs are all bent down on the stick fixing but I don't think they effect the operation of the selector?

Can any one offer any insight in what to check?

I haven't removed the stick to examine yet as your meant to put it in forth to do that and I can't get the box into forth!

Any suggestion or similar experience I be grateful to hear. I was hoping to get the car on the road in the next few days so really down't want to have pull the box as it'll probably put me back months.

Thanks,

Mark

[rgh0]

Hi Mark
Check the lever and or the rubber gaiter is not jamming on the console or chassis as you move it into 4th gear.

Try removing all the console and gaiter and drive it without them in place and see if the problem goes away or whether you can see it jamming anywhere

cheers
Rohan

[john.p.clegg]

Mark
If you have to remove the stick or gearbox,putting it in 3rd will do. Just don't leave it in Neutral....

John

[mbell]

Thanks. Already removed the console and gators to make sure there was no interference, which there isn't.

Sounds like the next step is to remove the stick and see if anything a miss can be seen.

I am guessing I shouldn't take the box out of 3rd with the stick removed?

[john.p.clegg]

Without getting too technical,if you were to put it into neutral,the side to side slidey thing could come adrift from the uppety peg and is a bugger to re-fit.

John

[Mick6186]

Mark,
I had trouble with my 5 speed box and have recently removed it and taken it to pieces (3 times!!).
The 1st to 4th gears have a fairly straightforward selector system which is reasonably foolproof so the problem may be within the gearbox.
The reverse and 5th gear selector system is a convoluted affair which is a nightmare to put together until you have made a few mistakes and learnt from them.
If you do need to take the box apart the manual is good, although there is one part that can cause a major problem if you interpret the text as I did. Beware of the 'press in the bearing by progressively tightening the front cover bolts' or a similar phrase.
I dismantled and rebuilt the box with no special tools, but it's not easy!!
Mick

[mbell]

Thanks John, Mike & Rohan.

I haven't yet figured out how the 5 speed box works but might have to spend some time doing that. I still don't understand what happens if you remove the gear stick in neutral apart from something drops out of place and I spent hours cursing while trying to get it back in place. I'll be doing my best to avoid that!

Given everything else about the box works as as Mike points out the 4th gear selectors system isn't complex or issue prone I am guessing/hoping there nothing significant wrong with the box. The car's been laid up for 20 to 25 years I believe, so I am thinking that something in the box might not be moving quite as freely as it should and causing the issue. The questions is what and can I get it free'd with out removing the box?!?!

I really would like to avoid pulling the engine and box as I am on the verge* of having the car o the road. Pulling the box would probably put me back months as I just don't have the large chunks of time to spend working on the car that are required for that kind of job. As well as little to no gearbox experience and I'd also get side tracked with lots of while am there type jobs.

Thanks,

Mark

(* Also experiencing loss of ignition system/spark when hot that I need to investigate before its ready for the road.)

[rgh0]

Hi Mark

Get it on the road and drive it. If the 4th gear selection problem continues you can always fix it later.

cheers
Rohan

[mbell]

Hi Rohan,

That idea had crossed my mind and I am becoming more convinced that its the sensible approach to this rather than just head in the sand approach. The cars only been up and down the street to cover a mile or two so no real chance for the box to get warmed up.

The only question is whether to "risk" pulling the stick or not. Looking at the selector parts diagram the fact that it slots into 2nd ok suggests there should be enough travel on the selector mechanism to get 4th (?). So its unlikely to be an issue in the selector mechanism exposed by removing the stick. So not much point in pulling the stick at this point.

Thanks,

Mark

[john.p.clegg]

Mark
Quite right,and the fact that you can select reverse and fifth says that you have enough travel in the other plane...as Rohan suggested,go for a drive and see if it frees off.

John

[ericbushby]

Mark,
Loss of ignition when hot on mine was caused by a dodgy rotor arm. It recovered perfectly when cool.
Eric in Burnley
(currently hiding from the afternoon heat on the Pacific coast of Costa Rica)

[mbell]

Thanks Eric, I remember the thread and have pulled my rotor arm as a result. It's a new red one and looks to be in good condition, not ruled it out but not too suspicious of it.

I think the rev counter dropped straight to zero when it happened. So I am thinking it a power supply problem to electronic ignition, especially as I have it and the fuel pump connected directly to the starter solenoid. So going to start there...

Enjoy Costa Rica. Went there for our honeymoon would like to go back at some point. Teaching the wife to drive a manual car on foreign roads was a good starting test of a marriage....

[mbell]

After 150 miles it's still not going in to fourth. So bitten the bullet and pulling the engine and box. Guessing it's probably excessive play in the input/1st motion shaft.

Got it stripped down this morning ready to remove the engine (planning to pull engine and box separately). So far discovered the upper bell housing cover is missing/chopped up. Doubt it has anything to do with the issue but something to correct.

[Chris]

Hi Mark. The early Lotus five speed box had a very narrow and weak bearing on the input shaft. This bearing is not up to the job of controlling the end float of the input shaft. To select fourth gear, which is a direct drive , the gear lever has to be pulled rearwards hence the synchro hub moves forward, to engage with the fourth gear. If there is wear in this input shaft bearing the synchro hub can push the shaft forward making fourth gear difficult to engage. This of course may not be the answer to your problem, but it is a strong possibility. If this is the case, a stronger bearing can be fitted but this requires some machining. I hope your problem is simpler to fix, but the bearing problem is something to be aware of.

Good luck
Chris

[mbell]

Thanks Chris, that's exactly what I was thinking.

Pulled the engine and box this morning. Not exactly a fun job.

With the box on the floor it's going into fourth fine! There's is some forward/backward movement on the input shaft going between 3rd and 4th. There a little bit of side to side movement but not massive amounts.

Guess next job is to get dial gauge out to measure the play and take the cover off to have a look.

Cheers,

Mark