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Thread: Strange feeling after reversing...?

  1. #1
    Join Date
    Dec 2008
    Location
    Adelaide
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    42
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    607

    Default Strange feeling after reversing...?

    Sometimes after reversing while turning e.g. out of a driveway, I get this held back feeling as I slowly pull away....? It feels like I have either flat tyres or I'm driving over a bump or something?

    Once the feeling goes away (a few meters) everything is as normal...

    Has anybody else felt this feeling?

  2. #2
    Join Date
    Oct 2009
    Location
    Perth, WA
    Posts
    4,540

    Default

    Reversing full lock?

  3. #3

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    Try turning the rear diff off next time you reverse by leaving the hand brake one click up. Not saying you should do this all the time, but just see if it makes a difference.

  4. #4
    Join Date
    Dec 2008
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    Adelaide
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    Quote Originally Posted by kmh001 View Post
    Try turning the rear diff off next time you reverse by leaving the hand brake one click up. Not saying you should do this all the time, but just see if it makes a difference.
    I have a MPS3 switch installed so I can try that next time

    Rogwick I think it would be almost full lock.... what are your thoughts?

  5. #5
    Join Date
    Oct 2009
    Location
    Perth, WA
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    Default

    I can't remember where but Doug made some comments related to full lock and motor strain and how some members stall when reversing.
    I know sometimes when I reverse and I near full lock I sort of pump the throttle so I don't stall or make sure I have enough revs. The car seems to struggle a tad when on full lock.

    Think I found the thread, have a read here and see if this helps clutch-upgrade-mazda-6-mps in particular...

    RD415, Hi. Re the stall on tight reversing, mine does that too. It's not the clutch - it's transmission wind-up that locks everything up, due partly to the loads imparted by the limited slip rear differential, and the full time AWD. My Toyota Landcruiser also has the same setup, limited slip diff and full-time AWD and does the same thing. We have a car-park at our local shops that has a speed hump at the rear of each bay, so you have to back out tight, turn and transect the hump all at once. A lot of load-up. I have stalled the MPS6 there on occasion.

    Avoiding full lock turns under load is the easiest way to avoid this. If that is not possible, then you can do it in small bites perhaps. It can be overcome by application of more power, but that doesn't reduce the lockup, just enables you to apply sufficient power to overcome the only way the car is going to move and this is by scrubbing the tyres. Cars with fatter tyres will experience it more. You will note that it will not do it, or will do it less under otherwise identical circumstances, on a slippery/gravel surface, as these surfaces enable the tyres to slip easily and relieve the transmission wind-up. You will find that occasionally, the diff will click or groan as the plates slip, depending on the severity of the turn. It sounds painful but doesn't hurt the diff unless you make a habit of it.

    In short, no matter how big or how new, or how wonderful your clutch is, it will still do it.

    This is an issue often dealt with by 4WD drivers, most particularly where there is no centre diff to compensate. However, talking of making a habit of it, the mining industry used to blow up out lots of FJ45/55/65 gearbox transfer cases (no centre diff) that couldn't handle prolonged low-range 4WD use on tight turns when working underground, even on loose (but still hard and unforgiving) rock surfaces. These cars were often locked permanently in 4WD low range as part of the mine safety directives, so the boxes and transfer cases never got a chance and would last mere months in some cases.
    Last edited by rogwick; 30-11-2010 at 08:54 PM.

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  6. #6

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    Sounds like the trans wind-up to me. Quite often as you straighten up and pull away after a full lock reverse turn, there will be an initial click or two as the loads come off and the plates in the LSD reset themselves, then all is OK. Try repeating it on a loose gravel surface. As the gravel accommodates the drive-train tensions by allowing the wheels to slip, you should find that you should not experience this problem. That will pretty much define it as trans wind-up. Mine will only do it very occasionally on a hard lock reverse turn up a slight grade, over a speed bump on a sealed surface, all at the same time, as exists at my local shopping centre, as I explained in my (quoted by ROG) paragraph above. Basically nothing of concern, just be aware of it and minimize hard lock. The power steer pump doesn't like sustained full lock anyway.
    CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18

  7. #7
    Join Date
    Dec 2008
    Location
    Adelaide
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    42
    Posts
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    Thanks a lot for your knowledge, what you are describing is exactly what it feels like

    I will try to keep it off hard lock in reverse!

    Had me worried to start with!!!

  8. #8

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    MZSPD6 - just for the record, my Toyota Landcruiser does it too. It is a model with full time 4WD and a centre diff and a rear LSD. Reversing and turning hard up a steep drive at my last house it would actually wind up so the loads became very high, considering the wide cleated tyres. Its only avenue of relief was to dig up the brick paving! (Incidentally, where I have a tight turn into my carport, my MPS6 does that too). I'd have to get the Toyota out onto the road, then gradually straighten up and let the loads relieve themselves with a few clicks from the back end, then all was fine. At first I was sure I was going to strip teeth somewhere, but I got used to it. It happens less so with skinny tyres. The underground 4WDs on mine-sites are locked into 4WD low range as a safety precaution, and they are known to blow transfer cases routinely. We did them in less than 10,000km regularly. This was due to tight turns and reversing in rocky hard bouldery surfaces with NO centre diff (hence no diff action between front and rear shafts), meaning that there were few avenues of stress relief. It all finished up as heavy sideloads in the transfer cases which would come apart at the junction of casing walls and shaft drillings. With my old Series 2 Landrover (no centre diff), it was almost impossible to make a sustained hard lock turn in low range on a hard surface, so high were the transmission loads. Hope this helps.
    CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18

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