Gearbox crunches changing in to 2nd?

[UremaW]

 

Hi there. I've had my Supersport R for a year now - I built it last summer and completed the running in process in late spring this year. Ever since I've been able to use full revs, Ive found the gearbox crunches when changing from 1st to 2nd if the revs are over 4,500rpm.

I assumed that the clutch needed adjusted or bled, so tried this a few times to no avail. I changed the gearbox oil too just in case (PitA).

Eventually, with the 12 month warranty due to expire, I booked it in with Caterham (using Revolutions in Perth) to have them look at it. Unfortunately due to a series of unfortunate circumstances between the dealer and the factory, they ended up having the car for 2 1/2 months getting the gearbox out, sent down to Road and Race for repair, then back to Revolutions for fitting.

Complete nightmare missing out on the whole summer (and 2 booked track days and a proposed road trip with mates), but I was just glad to get the car back. When I picked it up, I was advised to keep the revs low on the drive home to let the box bed in.

I did a couple of hundred miles like this and all seemed fine, but when I first tried revving it above 4,500rpm again (with engine/fluids up to temp), crunch. Not good.

I've dropped it back to Revolutions again to have the box removed and sent down south, but have asked for a proper gearbox swap now.

I took a short (poor quality) video clip to demonstrate the issue. Holding the revs steady at about 4,500-4,750rpm in first, then changing slowly into second. It happens every single time.

http://youtu.be/UBfqQsK0pdQ

Has anyone else experienced this? Its the 5-speed Type-9 box. Brand new in July 2013.

 

cheers

Scott

[Mankee]

I find crunching gearboxes incredibly frustrating, so I feel your pain. You say that a faulty syncro was found and repaired but do you know exactly what part? I fitted new aftermarket baulk rings to my Type 9 when I rebuilt it and they were CRAP. Which meant gearbox out again to fix it.

I got BGH to do it properly second time round. They use reclaimed genuine Ford rings (if the customer doesn't want to go for brand new Ford rings), as there is no comparable quality aftermarket replacement. As part of the rebuild, they deburred the dogs on the gear and replaced the 1st/2nd syncro hub on the main shaft as well as the outer. My box had taken a battering before I bought it.

At the moment, I still get a crunch into 2nd. However, because my car is track only, I only change from 1st to 2nd when pulling out of the pit lane, and that is where I get the crunch. Even changing down at high revs from 3rd to 2nd, there is no problem.

Chris has never had a problem reusing baulk rings, but because I perform the offending crunch very rarely, the "new" ring doesn't get a chance to bed into the cone of the used gear. He suggested that, for a road car that stops at junctions and goes up through the box normally, the bedding process will sort itself out after a few hundred miles and the crunching disappears. It sounds like you've already driven it around for a bit though. He did outline a method to speed up the bedding in, but I've not had a chance to try it yet. I have no reason to doubt his method either.

What box oil are you using and how much?

[Nigel Riches]

Type  9 'boxes are quite fussy about oil type, fully synthetic 75/90 Castrol Syntrax worked well in my BGH' box. 

I have recently filled my gearbox with Redline Lightweight Shock Proof Fully Synthetic oil, not tested on the road yet, but it will find any weakness in gaskets or seals, how do I know this? 

Fill quantity seems to be around 1.5l.

Regards, Nigel. 

[Jerry Auton]

If it was mine I would ring Phil at R&R and have a chat. I appreciate that you may be reluctant as it's is a warranty issue, however, a discreet conversation may help resolve the situation a little more swiftly.

[7 wonders of the world]

Speak to Steve @ SPC  he builds some of the best boxes around

Linky as the bloody link button on this new sodding site won't link in

 

www.spcomponents.co.uk

 

The baulk rings always get the blame, however in many cases it's not the ring at fault, often excess endfloat of the gear so the ring is in no position to do it's job, resulting in the driver using excessive force to overcome this issue which breaks the rings - replacing them wont cure the problem.

Heavy OE clusters with wide OE ratios don't help either when driven in a spririted manner.

Opimum capacity is 1.2 L the level plugs are misleading as there were many different heights depending on the application some allowing as much as 1.9 L - Redline MTL has a good reputation for giving good protection and a clean shift, I tried several oils in mine and found MTL by far the best - you will need 2 bottles since it's supplied in US quarts!

 

 

[revilla]

Linky: www.spcomponents.co.uk#sthash.OfDV1cWJ.dpuf
 

[7 wonders of the world]

Thanks revilla

[7 wonders of the world]

Thanks revilla

[Slipper man]

I know it is a new car, so you may not want to do this, but...

If the 5 speed box is like the ones I used to have before going to 6-speed cars, the top gear ratio is too high and the first gear far too low (it was designed to ensure Sierra's could do hill starts when towing caravans etc). BGH used to do a modification for not much money where they raised first gear and dropped fifth. It totally transforms the car and should eradicate the crunch you have in first/second changes, because the rev change would be much lower. 

Does the car crunch if you double declutch on changing up, by the way?