Overdrive problems

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  • #43040
    #43041

    Hi There,

    I have some odd overdrive (j type) problems with my 2500 S. It works fine in 3rd, but was becoming slow to disengage in 4th. Now 4th has stopped working all together. I tested the electrical circut with a 12 volt test light. The solenoid receives power in third (ie the tester light illuminates) but not in 4th? The fact that it works in 3rd dismissed any problems with the inhibitor swich and solenoid, so does that mean the problem is a mechanical one in the gear box? If so….that sounds like a bit of a pain to fix! Ive checked the oil level too….Id be glad to hear from any one with some expertise on the matter….

    The good news is, its been stinking hot, and the recently installed air con (at great expense to the management) is working well!

    Cheerio,

    Matt

    #43042
    straylight
    Participant

    I’m no expert on the J type overdrive matt, but the triumph dolomite guys pointed everyone to a technical site in the USA which has some excellent information and diagnostics for it.

    http://www.buckeyetriumphs.org/technical/technical.htm

    follow the links to the J type. It discusses everything from routine maintenance, overhaul, fault finding and is written in a clear way with lots of pics and diagrams. The guy who wrote the guide is a dead set legend.

    The site has a wealth of other triumph info as well.

    But, I’m thinking the inhibitor switch is releasing in third but not in 4th. Idle guess though.

    good luck

    stu

    #43043
    britishcarfreak
    Keymaster

    Has to be the inhibitor switch on 4th gear. Wire could have fallen off the switch or broken.

    Given that engine RPM contributes to the effective engage/disengage speed a slower revving car i.e. in 4th gear vs 3rd gear would appear to be a bit slower. Getting worse over time is odd though. The inhibitor switch wiring could have been very much worn through and carrying a very weak signal – and perhaps now is broken completely.

    It is possible to get access to the switches and check the wiring is in place. I seem to remember with the engine off and the IGN in the ON position you used to be able to hear an electrical click when moving through the gears i.e. N to 3 or N to 4 (with the OD switch IN). Try that and listen to see. If you know how to set up a voltage check with a multimeter or even a lamp then you could test for power at the 4th gear inhibitor switch etc.

    I’d bet money – and lots – on this being an electrical issue not a physical / mechanical OD issue.

    #43044

    Hi Fellas,

    Thanks for taking the time to reply. Ive found and sorted the problem. The wires that go from the gear lever overdrive switch, were badly frayed in the shaft of the gear stick. Funnily enough, there was enough electric signal in 3rd, but the shift to 4th was enough to stretch it some how, and wouldnt work…..Ive patched it up, will probably have to replace them properly one day. An auto electrician I use said they had repaired a few overdrives over the years, and it was always the switch wires…..though he thought it must be some thing else this time.

    Anyway, it was a simple fix in the end…..did i mention my air con? perfect weather for a cool classic!! I know ive been gloating about it, I hope it dosent blow up…….

    Cheerio,

    Matt

    #43045
    JamesHarris
    Participant

    I’ve only just read your OD problem and was about to suggest taking a look at the wiring that runs through the gearstick as the same thing happened to me but then got to the last post on the subject to find you had done exactly that. 9 times out of 10 it is usually the simplest thing that buggers the workings of anything up rather than the complicated. Great when it works though isn’t it?
    I also found that if the OD is getting a bit tardy at coming in but does if you give it a bit of welly it means the oil level in the OD unit is getting low. The increased pressure of the extra speed gets the OD to kick in eventually and these old boxes unless overhauled with new gaskets every decade or so do drop oil. Another problem I have come across is the mesh filter found by taking the rectangular plate off of the bottom can get clogged up. One other thing, don’t by pass the inhibitor switch to get OD in the other gears. It buggers the box eventually especially if it is accidentally engaged in reverse. You pick up all sorts of info after 23 years of these lovely cars. One last point I have just remembered about the OD units, if ever replacing the solenoid on the side of the box do not be tempted to grip it with molegrips (don’t know if that’s what they’re called down under) as the solenoid unit is easily damaged by doing so.

    #43046
    britishcarfreak
    Keymaster

    Molegrips = Multigrips in Australia.

    Changing the oil in the box is a good idea too. So many of these would not have had an oil change for 10 years or more surely. These boxes do wear and they certainly end up with a bit of metal filings in the oil. I seem to remember a magnetic plug that catches a fair bit of it though.

    #43047

    What oil for the box would you recommend? I know the manual says (off the top of my head) hypoid 90, or something, but lubrication has evolved somewhat and perhaps there is something else I should use instead?

    Matt

    #43048
    Stuart
    Participant

    Auto trans fluid works well in the gearbox. I have had it in mine for a few years now with no problems (yet)

    #43049
    JamesHarris
    Participant

    Goes without saying about the oil as the damned stuff would be all down my front while doing the gaskets. Have you ever noticed what happens to your skin in the bath whilst washing off hypoid? I know, I know, you’re not supposed to get any of the carcinogenic stuff on you but it happens unless you’re wearing a bio suit looking like special branch on a crime scene.
    Thanks for the molegrip translation.
    All the best to you fellas.
    James

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