 | Home > Technical > hi lo revs switch |
 
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
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that's what mine does  |
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21st Jun 2015 2:28pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308  
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night before last I removed the front prop and yesterday I could barely drive the damn thing in terms of getting a gear that didn't look like I was learning to drive - put that partly down to the rear drive flanges needing replacement due to wear.
put the hi/lo switch back in and tried as I have before by trying to extend the length of the linkage from the hi-lo lever to the transfer box. gear changes this morning not a problem. not knowing how exactly the transfer box works could it be that extending the linkage now put some constant pressure on the mechanical part that selects hi/lo which would make a difference. **Steve** Miserableoldgit - didn't you post something sometime back about struggling to get a smooth gear change no matter how hard you tried and it turned out to be hi/lo or diff lock that wasn't properly engaged? how sensitive is the mechanical input to the transfer box for hi/lo - is it possible something is preventing it from being pushed fully home? WOW! found it.......a bit more practice and you can call me MAL. 
I recently needed to get one of my trailers on to a bit of very wet ground and I thought I'd get it as far as I could with the Defender and use one of the tractors to finish the job should the trailer get bogged. As it was I got the trailer backed to where it needed to be using the Land Rover in low box, difflock engaged. Having got back on firm ground I disengaged difflock and selected hi range and parked up nearby for the night. The following day I needed to use the Defender but once moving noticed that the gear change was awful ...I couldn't get a smooth change without a substantial clunk no matter how hard I tried, the whole transmission seemed slack and rather like some of the old clunkers I'd had in the past. The difflock light was not lit, the range lever was where it should be, the rolled freely and transmission did not feel to be winding up so I immediately imagined I had the start of an issue which peed me off as the vehicle was new just recently. Pulling out of a junction at the bottom of the lane here I suddenly lost all drive ....but I had an inkling what had happened and sure enough I found the Hi Lo / Difflock lever in neutral, I got it back in to high range on the fly and instantly the transmission was back to normal with no undue noises, clunks, bangs or slack. So despite feeling like the lever was fully engaged in reality it was only partially in ....and this from someone who has been around Defenders and other 4x4's for a few years. So this is exactly how it feels..... short of extending the linkage rod is there anything else that can be adjusted to ensure hi range is FULLY engaged? Please? |
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24th Jun 2015 6:18am |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610 
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The linkage rods are there for that very purpose. Adjust if necessary and move on........literally!
High or Low range will do! If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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24th Jun 2015 7:22am |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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will give it another go tonight. someone suggested they were simply adjusting the position of the lever (more a cosmetic thing than actually changing anything mechanically if that makes sense). would this be the only adjustment? other than the rod there's nothing on the box that would prevent the hi range from being fully enganged? thanks Mal. |
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24th Jun 2015 7:28am |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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Even if it does just alter the lever position it will give you more leverage surely? Please mark it before you adjust anything. That way you can 'roll back' to where you started and prevent another proverbial 'marathon slipping into the abyss can o' worms!' You're not going to draw me in any further that's my lot! Hope you have a fantastic holiday and sincerely hope there's no internet connectivity whatsoever where you're going. We need a holiday too!
 If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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24th Jun 2015 7:59am |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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24th Jun 2015 8:12am |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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thank you BW.
so what is used to line up the indents - just the lever presumably. how when it's lined up does it remain lined up? I presume if these aren't correctly lined up it can jump out of hi range and into neutral (I've had that happen when accerating out of a right turn junction). assuming the linkages are well lubricated is there anything else that needs adjusting to ensure the indents line up correctly. I'd originally assumed this was done by adjusting the lever linkage length? thank you. |
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24th Jun 2015 11:39am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17473 
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The detent mechanism works (as detents do!) by having two notches on the shaft which carries the selector fork, the shaft slides past a spring loaded ball located in a machined housing in the gearbox casing. Consequently the shaft has two positions in which the ball engages one or other of the notches, and these hold the selector fork in the correct place to engage either the low or high dog clutches.
The difflock is a slightly more complex arrangement since the selector fork floats on the shaft between two bias springs, since there is a high probability of it baulking on engagement due to misalignment of the dog clutch, or baulking on release due to transmission wind up. The bias springs ensure that as soon as the baulk condition is released by virtue of the relative movement of the front and rear drivelines, the selector fork will either engage or disengage correctly. It is in this case the selector shaft, not the fork, which is positioned by the detent. There will be test on this later! |
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24th Jun 2015 12:26pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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thank you very much BW. spring loaded ball....a little bit like you'd have on a socket wrench to hold a socket in place?
presumably if this wasn't working very well the shaft wouldn't stick in the right position and hence it would be clattering but unlikely to drop out of high ration? is it common for these things to fail....could the transfer box be something else from the 'spares' bin I've blessed with? I also assume there's no realy way of telling if these balls are working correctly and from what I can interpret the gear lever just pulls / pushes the shaft into place and then held there by the spring balls. Presumably once engaged there should be an increased amount of effort to dis-engage rather than simply moving the shaft? |
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24th Jun 2015 12:47pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17473
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Exactly the same principle, an excellent analogy.
If for whatever reason the detent mechanism had stuck or failed, the shaft would be free floating and may well jump out of gear. The likelihood of this happening would depend on many factors, including the geometry of the of high and low gear dog clutches. I doubt that anything would "clatter", it would either be in gear or out of gear.
No, but not unheard of. Detent springs can break, and moving parts get gunged up. If the transfer box has been properly services or is new, a failure is unlikely (provided it was properly assembled in the first place, of course).
Since the whole of your vehicle seems to have been built from components rejected by earthlings and assembled on Friday the 13th, anything is possible!
The only way really to tell is by feel, and it may require the linkage to be disconnected and the shaft moved directly. Alternatively you could strip down the transfer box....... |
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24th Jun 2015 12:59pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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Stripping down the transfer box forthwith is your best option!
If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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24th Jun 2015 1:21pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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thank you...will leave the strip down as a last resort..... rightly or wrongly will try 'feeling' for it first and adjusting linkage length. |
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24th Jun 2015 1:22pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6308
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do you think so Mal.
neighbours are going to love this tonight.......... I'll let you know how I get on but think it may end in 
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24th Jun 2015 1:24pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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No! Just trying to keep you busy! When people tire of this thread you could always start another? You could name it 'Caterham's Almost Positively Last Problem! (perhaps, maybe, alright I fibbed the last time.)'
If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! Last edited by K9F on 24th Jun 2015 1:30pm. Edited 3 times in total |
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24th Jun 2015 1:25pm |
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