6 replies to this topic

[bloodythingwontstart]

Evening All,

 

Recently refreshed a gearbox for my 89' 998cc, as the original wouldn't hold second and was starting to crunch into third. New bearings, baulkrings, layshaft, second gear, detent balls/springs etc etc. A budget build but repalcing all worn components. My first gearbox build, following various guides and some great threads on here. Re-used the original verto clutch which looked servicable with a new thrust bearing. Primary and idler end floats checked and new thrusts/C clip installed to get all into tolerance. Whipped the engine out and swapped the gearboxes over. 

 

Chuffed to manage a run round the block with all gears selectable. However, 1st/2nd can be quite hard to select with the engine running and stationary and reverse goes in with a crunch unless the car is stationary with the clutch engaged for a good 20 seconds or so. All gears select lovely with the engine off. On the road 1st/2ndselect better but notchy. 3rd/4th seem fine. Suspected the clutch was dragging slightly.

 

Since renewed all the mechanical clutch actuating components as the ball end was worn and bled up the hydraulics. Checked I was getting full travel of the clutch plunger (6.5mm as per the Haynes manual for a verto) No change. Tried backing off the clutch stop bolts to allow more plunger travel, still no change.

 

Tried jacking up the car with the front wheels in the air and selecting gears with engine running. Small amount of movement from the wheels as the gear is engaged and then no further movement of the wheels suggesting the clutch can't be dragging badly?

 

Stripped the clutch out with the engine warm and checked the primary gear spins freely on the crank, which it is. Measured 5 thou end float. 

 

Any ideas before I bite the bullet and buy a new clutch?

Normally I would just replace it but the sound of getting the clutch/flywheel balanced sounds expensive when the gearbox rebuild exceeded the budget 

 

To summarise:

Gearbox rebuilt

Original clutch (verto)

Slave bled - getting full travel of the plunger to the stop on the wok.

New plunger, clutch arm, clevis pins

Primary gear doesn't appear to be pinching the crank.

All advice welcome, many thanks!

[alpder]

That wheels-in-air test is an interesting idea: you could try repeating that and see how far up you can lift the pedal (in gear) before the wheels start to twitch - if a reasonable distance then that would show that the issue is unlikely to be lack of clutch throw.

 

And reverse crunching except when stationary, would be expected.

[Spider]

It does sound like the clutch isn't fully disengaging. Sorry, I'm not familiar enough with the Verto Clutches to suggest anything there. Noted that you've checked the end float on the primary gear, but has it got genuine bushes fitted or the after-market ones ?

Also, is the primary gear being pinched by the flywheel ? When that occurs, all end float of the primary gear is taken up and it becomes pinched between the flywheel and the thrust flange of the crank.

Regarding it being stiff to select 1st / 2nd gear, drive it for a bit / do a few more shifts and it'll likely loosen up.

[bloodythingwontstart]

That wheels-in-air test is an interesting idea: you could try repeating that and see how far up you can lift the pedal (in gear) before the wheels start to twitch - if a reasonable distance then that would show that the issue is unlikely to be lack of clutch throw.

 

And reverse crunching except when stationary, would be expected.

 

Bite point is about halfway up the pedal and I could lift the pedal a good inch or so before any wheel movement, which I assumed to be fine.

 

It does sound like the clutch isn't fully disengaging. Sorry, I'm not familiar enough with the Verto Clutches to suggest anything there. Noted that you've checked the end float on the primary gear, but has it got genuine bushes fitted or the after-market ones ?

Also, is the primary gear being pinched by the flywheel ? When that occurs, all end float of the primary gear is taken up and it becomes pinched between the flywheel and the thrust flange of the crank.

Regarding it being stiff to select 1st / 2nd gear, drive it for a bit / do a few more shifts and it'll likely loosen up.

Original bushes I believe, I just inspected the primary gear and refitted. I couldn't see any particular evidence of this, is there any method to check?

I will pull the primary gear off at the weekend and have another good look at it.

 

Thanks for the advice guys,  the worst thing is the car has been off the road for a good few months and as the old gearbox was so bad I can't recall if it was like it before or not!

[bloodythingwontstart]

Pulled off the Primary gear this weekend and had a good look. 

Couldn't see any particular evidence of primary gear binding. The crank is marked around the front bush area but no worse than before the rebuild. Cleaned and reassembled and measured the end float at 4/5 thou. Primary gear rotates freely and smoothly.

Lapped the clutch to the crank and reinstalled the clutch but ran out of time to get it out for a test. 

Snapped some pictures if anyone has any thoughts on the condition of the primary gear bushes.

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 20250316_093938.jpg   27.53K   0 downloads

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As always thanks for the advice!

 

[orac69]

Potential clutch drag issue aside,  a wise old mechanic friend who worked on minis for 40 years gave me a tip once for sorting a "notchy" first gear.  He reckoned you should find a big cark park and drive easy in reverse for 1/2 - 3/4 mile.  I dont recall what it does exactly internally, but I have done exactly that on my own notchy spi and to be honest it made a noticeable difference.

[ThermalEvent]

I have exactly the same issue with my Mini and its the aftermarket primary gear bushes in my case. 1st/2nd clunky but 3rd/4th fine engine running. Engine off, all gears OK.

When it's up to temp it's better but still not as good as I had hoped. 2000 miles later and its finally becoming acceptable I assume due to increased clearance between bushes and crank. I dreaded driving in traffic due to this and forcing it into gear.

You mentioned end float but what's the clearance between bushes and crank?

I believe aftermarket primary gear bushes are not actually built to the same OEM specced ones but others on this forum know much more about it than me. I'm sure AC Dodd mentioned you need to have slightly more clearance for the substandard aftermarket ones.

It sounds like you haven't replaced them but thought it was worth mentioning.