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Speedo - Trigger Wheel


Taped_Finger

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Wondering if someone is able to help me with the issue I am having with the speedo on my 310R.

When the speedo reaches about 70mph it starts to stutter then as I increase the speed the speedo just gives up and drops to zero, once I lower my speed to below 70mph the speedo springs back to life.

When I build the car in 2020 I installed the speed sensor with the earth modification wire to the rear ARB mounting bolt.

Not sure if it's the actual speedo causing the problem or the sensor, I've had a look at the sensor tonight and all looks fine and I'm getting the light beam switch on and off when I rotate the wheel.

Any ideas what it could be?

Thanks

David

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Having another look at the speedo sensor, it actually looks like the prop shaft may not be seated correctly.

As the sensor is only covering half the teeth face

IMG_1366.jpg.733303a271909742968947bb78de39be.jpg

It's just come back from a Caterham dealer after a service, great!

IMG_1364.jpg.73bf79f02487c51255f738c237e98c9d.jpg

This asks the question why has the prop slipped out the diff?

 

 

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The trigger wheel is known to move on the tripod joint.  Caterham replace the driveshaft if this happens under warranty, after all its a part suppliers problem (GKN).  If your car is under warranty contact Caterham, if not then consider cleaning the rust, applying some strong Loctite and pushing it back into position. 

As how I know

491650DA-B1AB-458A-883F-BA3316DA96F8.jpeg.335a32938da9e2d573e0934a39fed3fa.jpeg

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Yep, this is a picture of my 420R.  It happened at the first proper dry track day, where I assume the driveshaft got hot from the disc.  It's a 2020 registered car, but the kit was supplied October 2019.  Apparently GKN now apply some form of green substance to secure the trigger wheel to the tripod joint, I wonder what that could be :-). 

Took as week to confirm the course of action (replacement driveshaft), but I am still waiting for parts.  That said I am not in a rush, I pushed the trigger wheel back into position to get a working speedo.      

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It seems to have started sometime in 2017 (ironically when the new sensor was released).  I know of one fellow builder with a 2020 delivered kit that had the issue.  So sometime between 2020 and 2021 the fix has been applied by GKN. 

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Once I get my engine back in, I'll turn my attention to updating the Speedo Guide to include the above problem.

If GKN are CC's official supplier of driveshafts (CC Parts are reticent on this point), has anybody asked them if they can supply spare reluctor rings?

JV

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The warranty contact is on annual leave for the next week for so, so I will not hear back from Caterham in a while.

As I was wanting to take advantage of the nice weather, is there a quickish way to push the trigger wheel back in place or is it a case of stripping the rear hub components off?

I don't have torque wrench that goes up to 270Nm for the hub nut, so if possible would like to avoid removing that nut.

My car has only done 1800 miles and I've not done a track day

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Mine moved back with a simple plastic trim leaver.  I removed the wheel and cleaned the rust from the area, then cleaned it again it's rubbing alcohol to promote good adhesion from the Loctite.  Applied strong Loctite and pushed it back.  I didn't remove the driveshaft from the hub, but I did remove the ARB bracket for better access (if you have one fitted).  New driveshaft arrived today, which is about a month since reporting the problem, the delay was mainly due to part lead times.  

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#11 John, last year when my Titan fell apart and I was thinking of fitting an SPC, at first I thought the SPC LSD only fitted the Ford diff so I considered changing the lot - diff, prop and driveshafts. 

After seeing the quite unusually costly shafts that CC  offer I tried to find a source at GKN but had no luck at all. 

That would be a good resource to have if anyone had a contact. 

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Hi Jonathan

Its a Ford box with the caerbont programmable speedo, you gave me some help with it when I bought the car, but unfortunately I had to shelve my plans for retrofitting something due to a house move and putting the car in storage (and a pesky virus!)

My car has driveshafts without reluctor rings, and I made several enquiries to CC to see if I could get one and retro fit, to no avail. I've bought a sensor, and one of my winter projects is a bracket to pick up the hub bolts at the front wheel. Apologies for the derailment OP!

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