Hardwyre Posted February 17, 2012 Report Share Posted February 17, 2012 Got two drive line issues here that I'm not really sure where to start. 1976 280Z L28 w/ 5-speed First one: When I'm at a stop and letting up off the clutch to start going, many times there is this moment where it seems like the engine is fighting a sudden increase in resistance, bogs down, and whole car sort of feels like it's tripped/stumbled. It only lasts for a brief moment and suddenly we're moving along just fine. If I feather the clutch and rev the engine a bit more, it doesn't seem to happen, but if I let the clutch out what seems like a just fine amount, it trips. It only seems to do it in first gear at a stop. All of the other gears while moving are fine. Second one: Lets say I'm rolling slowly in first gear, if the RPMs high enough, or I'm moving too slowly, the car starts to "bounce" off the drive shaft or something. It seems like there is an area of slop in the drive line that lets the differential and the transmission chase each other a bit. When I had the Z dyno tuned, it caused the car to buck or bounce until Travis gave it more gas. It doesn't seem to be caused by any variation in the engine as the RPMs are often steady. Ideas? Quote Link to comment
datzenmike Posted February 17, 2012 Report Share Posted February 17, 2012 Stock EFI? Maybe TPS? http://forums.hybrid...eguide-76-280z/ http://www.miata.net/garage/afm_fix.html Quote Link to comment
josh_t Posted February 17, 2012 Report Share Posted February 17, 2012 Got two drive line issues here that I'm not really sure where to start. 1976 280Z L28 w/ 5-speed First one: When I'm at a stop and letting up off the clutch to start going, many times there is this moment where it seems like the engine is fighting a sudden increase in resistance, bogs down, and whole car sort of feels like it's tripped/stumbled. It only lasts for a brief moment and suddenly we're moving along just fine. If I feather the clutch and rev the engine a bit more, it doesn't seem to happen, but if I let the clutch out what seems like a just fine amount, it trips. It only seems to do it in first gear at a stop. All of the other gears while moving are fine. Second one: Lets say I'm rolling slowly in first gear, if the RPMs high enough, or I'm moving too slowly, the car starts to "bounce" off the drive shaft or something. It seems like there is an area of slop in the drive line that lets the differential and the transmission chase each other a bit. When I had the Z dyno tuned, it caused the car to buck or bounce until Travis gave it more gas. It doesn't seem to be caused by any variation in the engine as the RPMs are often steady. Ideas? the first problem doesnt sound like an issue. i kinda think that feeling is cool. you get just the right amount of "bog" on the engine and it vibrates a lot. if its the same thing, then i almost shoot for that when i drive a stick at low speeds. its just from not having enough gas at a low rpm and a tiny bit too far out of the clutch. it seems to be a really fine line between getting whiplash and getting a normal, smooth start. and that happens on that line. my dad used to drive his stick shift cars like that 24/7 and nothing bad ever happened. i've never heard of the second issue. Quote Link to comment
RedBanner Posted February 17, 2012 Report Share Posted February 17, 2012 What do the upper diff bushings look like? If therr all warn out it could tourque up under power and be a bit loose when not, and twisting at stops maybe? Could be the same thing, im wrong alot tho. Quote Link to comment
DAT510 Posted February 17, 2012 Report Share Posted February 17, 2012 My G20 did this all the time! if going slow enough like through a parking lot, it would fluctuate with RPMs sorta like i'm pumping the gas, but it would fluctuate maybe 100rpm Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 Stock EFI? Maybe TPS? http://forums.hybrid...eguide-76-280z/ I love the fact you quoted my own TPS adjustment guide. :) But no, it's not a stop TPS. I'm running Megasquirt with a variable resistor TPS from an Altima. Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 the first problem doesnt sound like an issue. i kinda think that feeling is cool. you get just the right amount of "bog" on the engine and it vibrates a lot. if its the same thing, then i almost shoot for that when i drive a stick at low speeds. its just from not having enough gas at a low rpm and a tiny bit too far out of the clutch. it seems to be a really fine line between getting whiplash and getting a normal, smooth start. and that happens on that line. my dad used to drive his stick shift cars like that 24/7 and nothing bad ever happened. i've never heard of the second issue. Thing is, it's not a bog, it's like something is binding up, causing the car to lurch. I know the bog and vibration you're talking about, like when I start in 2nd gear. That I'm okay with. What do the upper diff bushings look like? If therr all warn out it could tourque up under power and be a bit loose when not, and twisting at stops maybe? Could be the same thing, im wrong alot tho. I haven't crawled under the car since it's been wet and I've been lazy. I wanted to get some ideas of where to look first. I'm pretty sure all the bearings and bushings are either stock, or old replacements. I have a whole Energy Suspension kit I need to install some day, just haven't wanted to start that project yet. My G20 did this all the time! if going slow enough like through a parking lot, it would fluctuate with RPMs sorta like i'm pumping the gas, but it would fluctuate maybe 100rpm I'll try and get some video of what it does soon here so people have a better idea of what I'm experiencing. Quote Link to comment
RedBanner Posted February 17, 2012 Report Share Posted February 17, 2012 If it where a hongderp id say bad injector, had a bucking problem with one, didnt feal "hopy" tho Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 If it where a hongderp id say bad injector, had a bucking problem with one, didnt feal "hopy" tho The second problem literally feels as if the drive line is bouncing off of the crankshaft, soaring through a little bit of play, and hitting the other end of the slack then bouncing back. I'm really not describing this well. Quote Link to comment
josh_t Posted February 17, 2012 Report Share Posted February 17, 2012 The second problem literally feels as if the drive line is bouncing off of the crankshaft, soaring through a little bit of play, and hitting the other end of the slack then bouncing back. I'm really not describing this well. well thats totally unlike anything i've ever heard lol. but the rear end shifting/torquing under load could be possible. i know its IRS so its not as common as a live axle shfting but same principal. Quote Link to comment
RedBanner Posted February 17, 2012 Report Share Posted February 17, 2012 If you take a block and jack up the front of the dif just till it starts to move the car, if it move at all before tge car does it deff move when accellerating Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 well thats totally unlike anything i've ever heard lol. but the rear end shifting/torquing under load could be possible. i know its IRS so its not as common as a live axle shfting but same principal. It's high time I crawl under there and start poking things with sticks. I need to install those new bushings anyways. :) I was wondering if the lurch problem (#1) might be due to an aggressive clutch disc, since I have no idea what is inside the clutch since I've never changed it since buying the car. Problem #2 I was thinking might be play or slop in the drive line, but I've never heard of a transmission having much play, or a rear end for that matter. I have heard of universals going bad. Quote Link to comment
Sealik Posted February 17, 2012 Report Share Posted February 17, 2012 (edited) Check the resistance in the...variable resistor TPS from an Altima....idle/part throttle/WOT???? Would give you the lurching and a few other possible symptoms And or.....Get it running 'shitty' and then check the plugs ASAP...isolate to one cylinder/injector Also....mark the position of the TPS...and then move it a smidge ...see if there is an improvement Edited February 17, 2012 by Sealik Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 Check the resistance in the...variable resistor TPS from an Altima....idle/part throttle/WOT???? Would give you the lurching and a few other possible symptoms And or.....Get it running 'shitty' and then check the plugs ASAP...isolate to one cylinder/injector I get pretty clean sweeps on the datalogs from the TPS. I'll take it for a spin tomorrow and run a log to see if I can catch anything during the lurching... I might have a flat spot in my fuel map where the engine loads up... I haven't noticed a lean spike on the A:F gauge though. Good idea with checking the plugs, I haven't done that in a while. Quote Link to comment
Hardwyre Posted February 17, 2012 Author Report Share Posted February 17, 2012 If you take a block and jack up the front of the dif just till it starts to move the car, if it move at all before tge car does it deff move when accellerating So if I can raise the differential a little and NOT have the car/tires move at all, I might have some slop/play in my rear gears? Quote Link to comment
josh_t Posted February 17, 2012 Report Share Posted February 17, 2012 It's high time I crawl under there and start poking things with sticks. I need to install those new bushings anyways. :) I was wondering if the lurch problem (#1) might be due to an aggressive clutch disc, since I have no idea what is inside the clutch since I've never changed it since buying the car. Problem #2 I was thinking might be play or slop in the drive line, but I've never heard of a transmission having much play, or a rear end for that matter. I have heard of universals going bad. i have had more personal experience with the opposite. my b210 clunks in the rear end with really hard shifts. but there is no play in the u-joints. there is noticeable play in the rear end though. my dads mustang would make a little clunk when you let off of the gas quickly and so does our jeep. they all have or had a worn diff. i'm not worried about my b20 tho since i pulled the pumpkin and the gears looked good and there wasn't any major or strange looking wear, no shavings, and the contact pattern on the ring gear teeth was all normal and looked aligned properly. Quote Link to comment
josh_t Posted February 17, 2012 Report Share Posted February 17, 2012 So if I can raise the differential a little and NOT have the car/tires move at all, I might have some slop/play in my rear gears? you could also crawl under there and have the car in neutral and no parking brake, make sure you have wheel chocks or something though. and grab the driveshaft and twist it and see if you can isolate the play, if there is any. there is supposed to be a tiny amount but not excessive. the gears do have backlash. if anythings badly worn you will probably be able to tell without a doubt just by twisting the shaft. 1 Quote Link to comment
RedBanner Posted February 17, 2012 Report Share Posted February 17, 2012 I had a ranger on or rack with a bounce and squeek, I started it and put in gear on the rack and me and 4 other guys all swore it was the trans. Found the rear joint had crushed the bearing into powder. Quote Link to comment
I'm BLUE Posted February 17, 2012 Report Share Posted February 17, 2012 Ujoints fail .... and can be un detectable by slop test ... rust shut .... and ..... just be a problem Hardwyre ... if you haven't done your u-joints in driveline ir halfshafts ..... in a while .... expect to be doing them soon .... s30 cars are very prone .... :lol: Quote Link to comment
I'm BLUE Posted February 17, 2012 Report Share Posted February 17, 2012 If you take a block and jack up the front of the dif just till it starts to move the car, if it move at all before tge car does it deff move when accellerating So if I can raise the differential a little and NOT have the car/tires move at all, I might have some slop/play in my rear gears? Be extremely careful doing this ..... bottom mounted rubber diff mount means that if you put car weight on pinion nose ... you risk tearing the mount more or period if your limiter strap is bad since the rubber is on the bottom holding the diff down ..... but is neccessary to check ! Instead ... put car on jackstands .... jack up on front diff as banner suggested .... look for easy of movement .... just like a worn tranny mount or engine mount .... Hardwyre .... r200's do have some extra slop .... they will run with slop ....if you're not lead footed like me :D Driveline u-joints go out a lot! !!! Especially cheap replacements .... go to six States driveline off of Columbia boulevard and i-205 .... they are great to work with. Build a front pinion strap ... hook it over front .... profit $$$$ .... get a new front diff mount from msa around $60 if needed. ... put Poly bushings on mustache bar .... if needed look up rtz's front diff build on hybridz. Tighten rear outer bolts to hubs on halfshafts .... Rear diff gear wear, splines wear, u-joint wear, stub shaft fatigue, etc ... are all going to contribute to clunky rear end stuff on higher mileage and abused vehicles. Just drive it and enjoy it ;) 1 Quote Link to comment
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