throwing the car sideways

[SuperBuickGuy]

I thought I'd solved the problem, but not. On my road there are a series of whoops (aka rollers), and if I'm going fast enough the car will unload the rear wheels and throw the car to the right (tail first).... today I seriously wondered if I'd get it straightened out in time.... I did, but I really need to fix this issue....

thoughts?


(everything under the car is new except the differential and the trailing arm bushings)

 

[mrvette]

All I can say is to describe my setup, 360 lbs plastic VBP rear spring, Bilstein sport shocks, 275/50/17 Nitto tires in rear, but they are NLA, so in the futures it's going to have to be same as front 255/50/17

front is 460 lbs VBP springs, with same shocks....I have a cross brace on the front upper a arms, and a rack steering setup....

I still can not hit the gas hard to accelerate out/around a turn, I have to be really careful.....

:suicide::sos:

 

[MYBAD79]

sloppy trailing arm bushings can make the rear unpredictable, how badly worn are yours?

do you have a rear sway bar ?

driving slower is not an option

 

[SuperBuickGuy]

I put a sway bar on it, thought it was causing the problem.... but no, without the bar, same problem....

it's got to be the bushing, but why it isn't loose when pried on with my 2' bar is beyond my comprehension.

 

[Garys 68]

How much play in the diff side axle yokes?

 

[racervette69]

I would check the rear alignment again, if you havent already. Has to be a change in alignment.

 

[mrvette]

I put a sway bar on it, thought it was causing the problem.... but no, without the bar, same problem....

it's got to be the bushing, but why it isn't loose when pried on with my 2' bar is beyond my comprehension.

:shocking: What KIND of sway bar?? one of the stock ~1/2" bars or one of the thick ones from like VBP?? I had one on there about 3/4 thick from VBP and it was a super PIA, took it off, much better with nothing, I have a stock bar in back now, and a ~3/4 stock soft bar in front, I did have a monster in front, but it's gone too.....:beer:

 

[SuperBuickGuy]

How much play in the diff side axle yokes?

none, but that makes me wonder about how slop in the rear differential might be present and affecting the situation.... I've had concerns about the rear diff, and play inside would change the camber of the wheel - which would pull me to that side (especially if that side was more than the other side)

what do you think?

Alignment:
I've aligned it, more than once

It's the thicker sway bar, but the problem exists with or without the sway bar on it.

 

[Garys 68]

Are you saying the sife yokes dont move in and out at all? Even new side yokes have a little movement.
The ends of them ride on the diff cross pin and wear. They're prevented from coming out by a clip. When the end of the yokes wear, they move in and out more than they should. This makes the rear end feel like you're on ice when they shift.

 

[SuperBuickGuy]

sorry, was reading yoke thinking u-joint...
yes, they move in and out - but if they more more on one side than another - that'd do what I'm suggesting?

I think the clutches are worn in the diff, which would make the left side go further out than the right side at full extension.... which could through me left (at least, this is my current thinking....) thoughts?

 

[Belgian1979vette]

Gary is right. My clips originally in my car where gone when I drove it. Made it unpredictable.

 

[MYBAD79]

I just replaced my side yokes but I also added upper strut rods and changed the spring at the same time, probably a bad comparison to what you have... but anyways, with the old worn yokes the car did not handle good at all. If you add worn trailing arm bushings to the mix then there's a lot of stuff moving back there ush:

 

[Garys 68]

The part of the side axle yokes that typically wears is the end that rides on the cross pin. When there is excessive in/out play, you will have problems. On mine, long sweeping "S" turns made it feel like you hit a patch of ice when they shifted. Very common problem. I think I bought mine from VB&P.
Unfortunately, you need to drop the crossmember and remove the diff in order to get off the back cover.

 

[MYBAD79]

yes, it's a pain having to drop the entire crossmember.

 

[SuperBuickGuy]

I just replaced my side yokes but I also added upper strut rods and changed the spring at the same time, probably a bad comparison to what you have... but anyways, with the old worn yokes the car did not handle good at all. If you add worn trailing arm bushings to the mix then there's a lot of stuff moving back there ush:

I going to add upper strut rods when I do the rear suspension - did you leave the clips out and cut off the ends of the yoke?

 

[MYBAD79]

I just replaced my side yokes but I also added upper strut rods and changed the spring at the same time, probably a bad comparison to what you have... but anyways, with the old worn yokes the car did not handle good at all. If you add worn trailing arm bushings to the mix then there's a lot of stuff moving back there ush:

I going to add upper strut rods when I do the rear suspension - did you leave the clips out and cut off the ends of the yoke?

i lowered the lower rods so the half shafts are not moving in/out anymore, I installed the clips in case I want to play with the setup later.... after 500 miles however I think I'm happy with the current setup.

check out my rear susp thread, lots of photos in there
http://www.vettemod.com/forum/showthread.php?t=7894

 

[SuperBuickGuy]

I just replaced my side yokes but I also added upper strut rods and changed the spring at the same time, probably a bad comparison to what you have... but anyways, with the old worn yokes the car did not handle good at all. If you add worn trailing arm bushings to the mix then there's a lot of stuff moving back there ush:

I going to add upper strut rods when I do the rear suspension - did you leave the clips out and cut off the ends of the yoke?

i lowered the lower rods so the half shafts are not moving in/out anymore, I installed the clips in case I want to play with the setup later.... after 500 miles however I think I'm happy with the current setup.

check out my rear susp thread, lots of photos in there
http://www.vettemod.com/forum/showthread.php?t=7894

It sounds like what you did answered a couple questions that were rattling around in my mind - 1) do you need to remove the clips when you're not changing the amount the driveshaft can move in and out, and 2) why not just take the clips off and be done with it (rather than cut them off.... it's not like I'm building a 4x4 that needs tremendous amounts of travel.

 

[mrvette]

I just replaced my side yokes but I also added upper strut rods and changed the spring at the same time, probably a bad comparison to what you have... but anyways, with the old worn yokes the car did not handle good at all. If you add worn trailing arm bushings to the mix then there's a lot of stuff moving back there ush:

I going to add upper strut rods when I do the rear suspension - did you leave the clips out and cut off the ends of the yoke?

i lowered the lower rods so the half shafts are not moving in/out anymore, I installed the clips in case I want to play with the setup later.... after 500 miles however I think I'm happy with the current setup.

check out my rear susp thread, lots of photos in there
http://www.vettemod.com/forum/showthread.php?t=7894

It sounds like what you did answered a couple questions that were rattling around in my mind - 1) do you need to remove the clips when you're not changing the amount the driveshaft can move in and out, and 2) why not just take the clips off and be done with it (rather than cut them off.... it's not like I'm building a 4x4 that needs tremendous amounts of travel.

Because the camber of the inner wheel changes so much the outer edge of the tire is all that's holding on the road.....

the force is on the tread, UNDER the lower strut, and so pulls the upper 'strut' (in this case the 1/2 shaft) out on the top, allowing the wheel to tip out on top, and so the tire tread is dead.....

:clobbered:

I had never considered the mechanical shape of the car, I ASSumed it was fine.....more concerned with updates and mods.....


:crylol:

 

[MYBAD79]

It sounds like what you did answered a couple questions that were rattling around in my mind - 1) do you need to remove the clips when you're not changing the amount the driveshaft can move in and out, and 2) why not just take the clips off and be done with it (rather than cut them off.... it's not like I'm building a 4x4 that needs tremendous amounts of travel.

if you lower the lower strut rods and have upper rods then yes, you can get away with sliding yokes. With my setup i could have done just that, sliding yokes, stock shafts instead of the sliding shafts.... mine is overkill.

 

[SuperBuickGuy]

It sounds like what you did answered a couple questions that were rattling around in my mind - 1) do you need to remove the clips when you're not changing the amount the driveshaft can move in and out, and 2) why not just take the clips off and be done with it (rather than cut them off.... it's not like I'm building a 4x4 that needs tremendous amounts of travel.

if you lower the lower strut rods and have upper rods then yes, you can get away with sliding yokes. With my setup i could have done just that, sliding yokes, stock shafts instead of the sliding shafts.... mine is overkill.

You have no idea how helpful that advice is - thank you

I was talking to a friend who owns a Corvette shop in Kirkland, WA - and he immediately pointed out that if I didn't have any clips the issue would be exactly as described.... he wants to sell me a 2.73 rear diff for $300 - I'm seriously considering it. I think it, plus the wide ratio super t-10 (chinese built, of course) in my 'vette would actually be the cats pajamas for what I'm doing. It has 3.08s in it now, and drives really well with them, so going down in ratio would be slightly doggish off the line - but on the autocross course, wide open interstates here, or even on the 2.5 mile course at Pacific Raceways - would be just right.... might even get decent mileage if I could keep my foot out of it.
and if I hate the number, I can always rebuild what's in there now and use it... or get that SBC 427 together.... there must be something about that general cubic inch - I've built 2 recently, and have one in the pipeline, and now considering yet another....