What is this violent jerking in driveline?

[IwantMKIII]

Now i've been driving around awhile now in the new car. All parts are from my previous ride except LSD keep in mind.

Its a violent stop and go rock. I can replicate it whenever I slow down (OFF the gas) in any gear below lets say 1500 RPM, the car jerks forward suddenly grabs pulls back the releases and jerks forward and repeat.

don't get me wrong, i've noticed this a bit in my previous car but not to this extent by any means. It also does it while cruising, if im barely on the gas it will do it though not consistantly like if i slow down in gear low RPM.

I was told a few things from other supra owners but im simply not sure.

*there are no strange vibrations/noises at high speeds if that helps, unless im barely on the throttle then it can happen at any speed.

I suspect LSD since its the only thing NOT from my previous ride...but i just don't really know why?


For reference:

Joint TO trans

line of sight from one joint to another, bearing to trans

line of sight bearing to LSD

Bearing joints

TO LSD

 

[IJ.]

Sight along the Uni joints and tell us what you see.

 

[IwantMKIII]

^ill admit, im very ignorant when its comes to driveline components, could you define the Uni joints please? And if there is anything specific I should look for, let me know. Ill try to get some pics up if my camera will take some decent pics under there at night

 

[ForcedTorque]

If you somewhat had it in the old car, and now it's worse in the new car, Why would you suspect the only thing you didn't bring from the other car?

 

[IJ.]

^ill admit, im very ignorant when its comes to driveline components, could you define the Uni joints please? And if there is anything specific I should look for, let me know. Ill try to get some pics up if my camera will take some decent pics under there at night

Look along the driveshaft and see if the Universal joint caps are all facing the same direction, what you're looking for is if the shaft looks twisted end to end.

 

[IwantMKIII]

If you somewhat had it in the old car, and now it's worse in the new car, Why would you suspect the only thing you didn't bring from the other car?

Could be a common problem, something that wasn't so severe on my car vs. this one.

 

[IwantMKIII]

Will do IJ

 

[IwantMKIII]

Well IJ, i didn't notice anything obvious, no twisting, nothing seemed out of line compared to something else. I took some pics, not sure they help much, maybe you can see something I can't (added in first post).

 

[IJ.]

It's hard to tell but pic 3 looks slightly twisted?

Also grab the Uni's and see if there's any rotation/up-down movement?

Best if the car is on stands and in neutral e-brake off to do this test.

 

[IwantMKIII]

Hmm, well that could take me a bit longer. My sis and brother are coming in tonight from Detroit so Ill check this out tomorrow if I don't get it done tonight

 

[Quin]

Does it feel like you don't know how to drive a stick? Like how the car bucks riiiiight before you stall out. That's kind of what it sounds like you're describing. Happened to a friend, his transmission was messed up and he had to get it rebuilt.

 

[IwantMKIII]

Does it feel like you don't know how to drive a stick? Like how the car bucks riiiiight before you stall out. That's kind of what it sounds like you're describing. Happened to a friend, his transmission was messed up and he had to get it rebuilt.

yes, yes it does.

Transmission has been rebuilt already. Relatively recently anyway, i would say within past 20k miles. No shifting troubles at all.

Any idea what would cause it within the trans?

edit: keep in mind it happens any gear

 

[7Mboost]

Tranny mount isn't destroyed or anything right?

 

[IwantMKIII]

Tranny mount isn't destroyed or anything right?

nope, very flexible and elastic, gaboonsviper35 would agree with me on this one as he was around for most of the engine/tranny transplant

 

[Quin]

In his case, he was missing a few teeth off of his first gear. Input spline all dorked up maybe? Shot in the dark man, couldn't tell ya in your case, as his only happened in one gear. Do what that old guy said.

 

[gaboonviper85]

Well... Ij can you find the pic I posted of what a fubar driveshaft looks like cause again I'm on my iPhone...

Adam...I saw this driveshaft before you installed it...your driveshaft is fine!

But this is what...I...think. The diff has major backlash (aka play)...the pinion gear and ring gear are worn out of spec....what this will do is.......while you accelerate at a decent rate and have a nice pull it doesn't jerk...BUT once you let off the gas it jerks and throws you forward...am I right?? This is a common problem in all old cars that have been beat to hell....basically your driveshaft acts like a torsion bar cause there is slop in the diff..

Adam.....put the trans in neutral and put the parking brake on....twist the driveshat in one direction then twist it in the other and how much twist could you get before it stopes?

 

[IwantMKIII]

^any time i lay off the gas under a decent acceleration it throws me forward, what do you think im NA or something

ill check the rotational play and such tomorrow. I saw you just called BTW, not a good time, ill hit you up tomorrow..

edit:
Quin best described the feeling

Does it feel like you don't know how to drive a stick? Like how the car bucks riiiiight before you stall out

 

[gaboonviper85]

nope, very flexible and elastic, gaboonsviper35 would agree with me on this one as he was around for most of the engine/tranny transplant

......85


Yes that transmount is ok....so is the ds

 

[IwantMKIII]

......85


Yes that transmount is ok....so is the ds

lmao, i don't know why i keep thinking its 35, btw im finding more and more im having wheel hop still on this chassis even with the new suspension looks like ill need some traction bars or something

 

[gaboonviper85]

^any time i lay off the gas under a decent acceleration it throws me forward, what do you think im NA or something

ill check the rotational play and such tomorrow. I saw you just called BTW, not a good time, ill hit you up tomorrow..

edit:
Quin best described the feeling

yes a sloppy diff will jerk you back and forth while coasting or if you start going down hill untill the motor holds you back and takes the play out of the diff...you could be going 40 mph and it can do it while you are maintaining rpms...its back lash...your driveshaft is acting like a big fucking spring..it could be transmission doing it but I doubt it cause when we drained the oil it looked great....bet if you drain the diff it will look like kindergarten arts and crafts glitter with some nice chunks of steel.