Guest 1982280zxttop Posted February 18, 2005 Share Posted February 18, 2005 i have a 280zx non-turbo, and every time i downshift, the transmission acts kinda funny, and my car jerks like, when someone lets off the clutch real fast, and i know its not me, because thats ill i every drive is a manual, i thinks its the tranny mount, but the mount looks ok.can someone plz help me! Quote Link to comment Share on other sites More sharing options...
datsunlover Posted February 18, 2005 Share Posted February 18, 2005 How are you downshifting? Just droping a gear, and releasing the clutch? (For starters, that is not the best way to gear down.. not trying to insult you, but do you know how to match revs/heal toe downshift?) Anyway, i'll bet it's probly 'slack' in the driveline causing the jerking. Loose u-joints and worn bearings in the tranny/rear diff can cause this 'slack' and it takes some finess to drive and shift smooth. Quote Link to comment Share on other sites More sharing options...
crazy280 Posted February 18, 2005 Share Posted February 18, 2005 You should pull out that tranny mount and take a good look at it. I had the same problem with my 75 280z and thought the mount looked okay until I pulled it and found that it was broken. Also check the differential mounts and all the crossmember bushings. Good luck. Quote Link to comment Share on other sites More sharing options...
Guest 1982280zxttop Posted February 18, 2005 Share Posted February 18, 2005 yeah, but heel/toe is more of a racing technique, right? i mean i understand what you are trying to day, but i shouldnt have to downshift like that right? i havent got the chance to check my other bushings/bearings/mounts besides my tranny one, but ill do it tomorra. any ways getting back to what i was saying. it only jerks when im going moderately fast, but when i go real slow, like 5-10 MPH it doesnt do that, does that help? plz post Quote Link to comment Share on other sites More sharing options...
Jolane Posted February 18, 2005 Share Posted February 18, 2005 When my differential mount broke on my 83, it jerked a lot when letting off the gas, and when shifting, accelerating. Check that rear diff mount while you are under there. Joshua Quote Link to comment Share on other sites More sharing options...
datsunlover Posted February 18, 2005 Share Posted February 18, 2005 I don't think the zx's are as bad for rear diff mounts.. the nose of the diff is bolted through to the x-member, and the rear mount it blted up to the floor area.. I would think if it was broken you'd hear some awfull racket back there... maybe the subframe mounts though... I supose you could call rev matching a 'racing technique' but I do it all the time, even in my beater 4x4 truck. Less chance of loosing control (ussualy when downshifting on ice/snow) and it's easier on your clutch, assuming you get it right. Think of it like this; When you push the clutch in, the driveshaft is still spining, but it's being 'driven' by the rear wheels as you are still moving forward. Then you drop to a lower gear, and let out the clutch. If there is slop in the u-joints, that has to get taken up before the car will start slowing down. It hapens quick yes, but I've had a few vehicles that have done this. My truck is one of them and it jumps and jerks all over the place if I'm not carefull and smooth with the shifting. Come to think of it, it could be a bad u-joint in one of your half shafts too.. Quote Link to comment Share on other sites More sharing options...
evildky Posted February 18, 2005 Share Posted February 18, 2005 sounds like your downshifting to first! most cars don't like that, I never downshift to first unless I am completely stopped or autocrossing Quote Link to comment Share on other sites More sharing options...
Jolane Posted February 18, 2005 Share Posted February 18, 2005 Hey Datsunlover, I had the rear diff mount break on my 83, and the rubber separated from the steel. I was not sure what the problem was at first, as it only made a thump when I shifted or used my engine for braking. I did not think it would make a big difference either, but when you consider the geometry of the rear subframe, it makes sense. The rear subframe is basically mounted with three points (a proper kinematic mount btw), the two subframe mounts on the cross member towards the sides of the car and the rear differential mount. The rear differential mount controls the fore/aft pitch of the diff and subframe, while the cross member mounts control the roll of the diff. All three contribute to the yaw of the diff. I will say that with my rear diff mount broken, it would slam into the floor and create a very load thump! If this is the problem though is yet to be seen, I think. Joshua Quote Link to comment Share on other sites More sharing options...
Guest 1982280zxttop Posted February 19, 2005 Share Posted February 19, 2005 i looked under it today, an the tranny mount was good, so ill check the others tomorra, and, to the guy about the heel toe thing, isnt that for like, downshifting into a turn or something? because i do that too when i autocross my 85 celica supra, but it was to my understanding that that was used for like drifting or donshifting efficiently into a corner, im talking about it jerking when im just driving down the street man. Quote Link to comment Share on other sites More sharing options...
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