jeromio Posted July 12, 2006 Share Posted July 12, 2006 Background: rear susp. totally rebuilt, disc brakes, custom front diff mount, 280ZXT CV axles, 4.11 R200 (85 200SXT). Changed diff lube about 2k miles ago. This is a recent problem, first noticed it last week while driving in the rain. Acceleration even while moving causes the car to lurch to the side a bit. But decceleration makes it really step out in the rear - this is in a straight line, not cornering. If I push in the clutch, no lurch. If I hit the brakes, no lurch. If I ease off the throttle, no noticeable lurch. But if I am on the gas, and then let off quickly, the car does a little skip to the side in the rear. So, I thought at first that it was just b/c the roads were wet and I hadn't driven in the rain in awhile. But the next day the roads were dry and it still does this. I jacked up the car and the suspension is tight - nothing is amiss or askew. I have 0 degrees of toe and everything is good with the suspension. I can spin both rear wheels by hand. So then I turned on the motor and put it in gear. Only the right rear wheel spins. If I gun the throttle, the driver's side will spin a bit, but only a bit and then coasts to a stop. If I block the pass. side from turning, the driver's side will spin. Un-blocked, the right rear (pass. side) is the only wheel that will turn in every gear. While in gear, the pass. side is spinning, I can turn the driver's side wheel, but it's as if it has no connection to the drivetrain. This seems to be consistent with the issue I have. If I have one wheel drive, then engine deccel would act like braking on just one wheel and that could certainly cause the car to wig out. Unfortunately I am daily driving this car to work every day now. Pulling the diff is not an evening job. But assuming I can get it out this weekend, what should I look for? I am presuming it won't be obvious. I have another gearset (3.54), but it's been sitting out (really rusty). Plus, I doubt I have all the right shims, etc. Anybody have any experience with shops - what's the typical turn-around and cost? As to what would've caused this, I dunno. No drag racing, occasional stomping on the gas and burning tires. But I have 4K miles on the LS1. My wife has been driving the car lately - I suppose she could be maniacking it....? It seems to be a random onset problem, not an "oh ****, I just did something that broke something" kind of thing. Quote Link to comment Share on other sites More sharing options...
kcelectronics Posted July 12, 2006 Share Posted July 12, 2006 If your diff is/was a LSD then yes it is faulty, if not its OK Quote Link to comment Share on other sites More sharing options...
evildky Posted July 12, 2006 Share Posted July 12, 2006 sounds like a regular open diff, although the wheel that doesn't spin might could use the brakes adjusted out a touch, also when you did this was the car supported by the diff or by the suspension, letting the suspension hang casues extra resistance in the driveline Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 12, 2006 Share Posted July 12, 2006 EDIT-- need to read before I post. When you got your car aligned was the thrust angle OK? Quote Link to comment Share on other sites More sharing options...
jeromio Posted July 12, 2006 Author Share Posted July 12, 2006 Non LSD. Thrust angle (same as toe, no?) is zero. I measured it myself and then got it confirmed by an alignment shop. EDIT to add that the brakes are fine - they're discs, no adjustment. I can fill in more background. I used to have a misaligned rear susp. due apparently to a poorly bored spindle pin hole (which I've learned is a relatively common problem). The car, with this toe out situation, was actually okay in the dry, but impossible to drive when the roads were wet - the rear was all over the place. It also wore rear tires very quickly, even with the sad little L28. So, I went to great lengths to correct this problem by fabricating a rear toe adjuster and modifying one rear control arm. But the rear susp. is now dead 0*. Both tires are parallel and the diagonal measurements are identical. I'm totally at a loss to find any other explanation for this new problem. When I let off the gas, it really feels like it's trying to turn right. And I'm talking rear steer kind of turning. It's a very brief little jerk, butit's very disconcerting. In other words, it's not like I have to crank the wheel when I deccelerate, this only happens for a second as I let off the pedal. I doubt that others on the road can notice anything, but I can definitely feel it. It's pronounced when going at highway speeds. Much harded to discern below 40mph. I'm hunting around for R200 diffs right now. Hate to spend money and time and not bump up in performance (as in, LSD or R230). I just don't have enough money or time to do a car project just now.... Quote Link to comment Share on other sites More sharing options...
mark Posted July 12, 2006 Share Posted July 12, 2006 You have something loose in the rear suspension. I know you have checked it but go back and check it again. Look at inner and outer control arm bushings and the suspension mounting points including the mustache bar mounting points. Something is loose, worn or broken. Good luck Quote Link to comment Share on other sites More sharing options...
331CI 280z Posted July 12, 2006 Share Posted July 12, 2006 The diff sounds fine. I have a '85 R200 out of a 200sxt in my car. I installed a Precision Gear Diff. You have an open diff, so one wheel spinning faster than the other is fine. It doesn't sound like the diff is the problem. Maybe wheel bearings or an axleshaft. Check your mustache bar bushings as well. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 12, 2006 Share Posted July 12, 2006 Non LSD. Thrust angle (same as toe' date=' no?) is zero. I measured it myself and then got it confirmed by an alignment shop. EDIT to add that the brakes are fine - they're discs, no adjustment. I can fill in more background. I used to have a misaligned rear susp. due apparently to a poorly bored spindle pin hole (which I've learned is a relatively common problem). The car, with this toe out situation, was actually okay in the dry, but impossible to drive when the roads were wet - the rear was all over the place. It also wore rear tires very quickly, even with the sad little L28. So, I went to great lengths to correct this problem by fabricating a rear toe adjuster and modifying one rear control arm. But the rear susp. is now dead 0*. Both tires are parallel and the diagonal measurements are identical. [/quote'] Thrust angle is not the same as toe angle. The wheels could be parallel pointing 5 degrees off to the right or left. This would cause your car to crab down the road, but sometimes it's tough to feel from the driver's seat. I don't know how accurate your diagonal measurements were, but in theory that should tell you if the thrust angle is wrong. But if the thrust angle was off, I think that would definitely cause the sensation you're getting. Aside from alignment could be a stuck caliper. Regardless, good luck with it! Quote Link to comment Share on other sites More sharing options...
jt1 Posted July 12, 2006 Share Posted July 12, 2006 It's possible it's in the diff- maybe a carrier bearing going out, but I think it would be making a noise you could hear. My guess is there's some motion in the vertical pieces or horizontal piece that supports the rear of the LCA's. The forces of accel/deccel are causing the thrust angle and/or rear toe to change as the load on the LCA's changes. Maybe loose bolts, worn bushings, or maybe the wheel bearings. John Quote Link to comment Share on other sites More sharing options...
jeromio Posted July 12, 2006 Author Share Posted July 12, 2006 It's not a caliper - both wheels turn with the same effort and there's no noise from a brake. My diagonal measurements were equal and the numbers from the alignment shop were all dead on. EDIT to add that the wheel bearings were replaced ~10K miles ago. Can't really hear any noises. Also, just to further clarify, when the car is in gear, jacked up, it's not like the wheels spin at different speeds. The driver's tire doesn't spin at all. If I floor it (which is a bit scary with the back of the car jacked up - worried it'll jump off the jack-stands and plow thru my garage wall), the driver's wheel will spin a little bit - pass. side is flying. Oh, and the ends of the A arms are jacked up a bit so the system can turn freely. I actually have the bindy zxt CV setup with the zxt flanges, so it makes the pass. side wheel catch a bit at full droop. I'll jack it up and look again, but I checked everything: front and rear diff mounts, spindle pin nuts, inner mounts and bushings, top isolators, everything was tight. Nothing looks broken. Can't move the wheels laterally at all. Also, and I don't mean to sound argumentative, but what would explain the specifics of this issue? If I slam on the brakes, I don't get this wierdness. This only happens briefly when I let off the gas. I don't necessarily have a good explanation behind my idea of what's happening - perhaps the driver's side pinion is binding slightly? That would make the system favor the pass. side. It does seem strange that it would introduce this much crooked behavior. I wish I had a lift.... Quote Link to comment Share on other sites More sharing options...
mark Posted July 12, 2006 Share Posted July 12, 2006 I looked at your web site (slow day here) and I would put my money on a loose bolt. Look at the control arm hangers(for lack of a better term) that support the rear control arms. Check all those nuts and bolts, anything that supports or locates the control arms. I hope you find it. I usually end up waiting for stuff to fall off. Easier to find but much more expensive to fix. Don't be like me. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 12, 2006 Share Posted July 12, 2006 If you really think it's the spiders, just turn one wheel by hand. You'll be able to feel any notchiness or resistance in the gears if there is any. Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 12, 2006 Share Posted July 12, 2006 If you put it in gear... jack up the rear and turn one wheel... the other WILL TURN THE OPPOSITE DIRECTION.... even with someone holding it providing resistance... check this.... even LSD diffs will perform in this manner... you just have to apply 50ftlbs of torque to break the clutches free.... Quote Link to comment Share on other sites More sharing options...
jeromio Posted July 13, 2006 Author Share Posted July 13, 2006 It gets worse. For the past few months I've noticed a sharp popping noise when I back out of the driveway too fast. Didn't really think anything of it. Now I hear that same noise when I downshift. It doesn't do it on a mild, coastie downshift, but it definitely sounds broken on a good, slow-the-car-down downshift. Junkyard drivetrain plus big V8 - I suppose it was inevitable. I realize that the 2 things (deccel lurch and popping noise) may not be related, but I guess I need to look for a new diff either way. I had all these long term "when I get the big fat raise/bonus" type of ideas of doing an R230 plus Z32 shafts/CVs plus 280 stubs plus 5 lug conversion plus new disc setup, plus new wheels and tires to go with and then the flares to accomodate them dreams. Now I gotta track down a decent R200 to get me by. Quote Link to comment Share on other sites More sharing options...
Shift Posted July 13, 2006 Share Posted July 13, 2006 'Popping moise" could be the diff mounts being worn. the torque bias could because of the halfshaft/diff bearings being more worn on one side, that and having an open diff could cause those symptoms. Quote Link to comment Share on other sites More sharing options...
jeromio Posted July 13, 2006 Author Share Posted July 13, 2006 'Popping moise" could be the diff mounts being worn.See the summary of background on my car in the first line of the first post. I have a deGroot diffmount - no noise coming from there.the torque bias could because of the halfshaft/diff bearings being more worn on one side, that and having an open diff could cause those symptoms.That makes sense and lines up with the behavior I'm experiencing. The car goes left on hard accel, goes right on hard deccel. I wish I could locate a drivetrain/differential specialist in this area. Can anyone recommend a good book on the subject of rebuilding R&Ps? The more I think about it, I would much rather rebuild one of the diffs I have rather than take my chances on another used part. Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 13, 2006 Share Posted July 13, 2006 They are really easy to take apart yourself.... I will be glad to help with your questions.. either here or PM me... I prefer the design and dissassembly of the R180s.. but a well worn R200 should be pretty easy as well.... for the R200 just be sure to mark the spacers when you remove the caps... then hold it over a wood floor when you drop the carrier out the back... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 13, 2006 Share Posted July 13, 2006 That makes sense and lines up with the behavior I'm experiencing. The car goes left on hard accel, goes right on hard deccel. That still sounds like thrust angle to me. When you accelerate it drives the rear of the car to the right, turning it to the left. When you decelerate there isn't as much weight on the rear, so the rear tends to move independently to the right. I think you've got the rear end pointed off to the right. That's my SWAG. Could be wrong, but that's what it seems like to me. I have a really hard time believing that the carrier bearings on one side is causing this issue. There is the possibility that something moved after you set the alignment, or that it was set and then the car or the bushings settled and F'ed it up afterwards. then hold it over a wood floor when you drop the carrier out the back... Or just use a prybar to lever it out. There isn't so much carrier bearing preload that you need to drop it on the floor, hardly any preload at all really. Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 13, 2006 Share Posted July 13, 2006 Well... my Nismo unit took a lot of effort to remove(easier to reinstall)... I would just be sure you do this over a wood surface... The parts are heavy and the balance of the unit changes drasticly when the carrier comes free... easy to drop it... Quote Link to comment Share on other sites More sharing options...
Shift Posted July 13, 2006 Share Posted July 13, 2006 jmortensen is probably right though. He seems to be right with these kinds of things. Its easier to check things than to replace things. If thrust angle is off then you just have to re-align, if not then its probably the bearings. Quote Link to comment Share on other sites More sharing options...
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