chatter vibration above 65mph, what is it?

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LaGrasta
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chatter vibration above 65mph, what is it?

Post by LaGrasta »

Hey guys, can't figure this one out. I jump on the freeway and get up to speed and chatter begins so bad my rearview mirrors vibrate so bad I can't use them. Here's what I checked:
  • wheels balanced
    shocks have no weeping or "float"
    repacked front bearings and tightened "snug"
    upper/lower ball joints are new
    good alignment
    everything is greased/lubed
    rear end is topped off
    U-Joints have no play
I bought a rear tranny seal today because while underneath checking the U-Joints I noticed it's leaking again. There is a bit of movement so maybe it's just this…?
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box
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Re: chatter vibration above 65mph, what is it?

Post by MountainManJoe »

What kind of movement?
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Re: chatter vibration above 65mph, what is it?

Post by LaGrasta »

Well, I got home tonight and swapped in a new tail shaft seal. Hopped back on the freeway and still vibrates like crazy over 65.

The movement was vertical, but slight. Honestly, after changing the seal, I didn't recheck to see if it still moved in that way.

I'm starting to wonder if it's the rear end or axles. But there is no leaks back there, no noise, and nothing else to make me think it's bad. UGH!, so frustrating.
I really appreciate any help or suggestion, I'm stumped.
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box
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LaGrasta
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Re: chatter vibration above 65mph, what is it?

Post by LaGrasta »

Is there a way to check rear bearings without removing the axles, wheels etc.?
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

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Re: chatter vibration above 65mph, what is it?

Post by astroturf »

Motor mounts, transmission mount???
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Re: chatter vibration above 65mph, what is it?

Post by LaGrasta »

both appear good. I took a jack and "lifted" it and no separation that I could see. Tranny mount is actually newer.
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

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Re: chatter vibration above 65mph, what is it?

Post by LiftedAWDAstro »

Pull the drive shaft again and move the u-joints through their range of motion. They should be free and smooth.
Current rides:
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2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

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Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy
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Re: chatter vibration above 65mph, what is it?

Post by 1Gary »

The second trans seal replacement might have to do with wear on the driveshaft yoke.A close inspection of that and if found,sometimes you can just emery cloth it and it will be fine and other times you just have to replace the yoke.I just dealt with that on my Sonoma.
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Re: chatter vibration above 65mph, what is it?

Post by LaGrasta »

Another friend just told me with his S10, he had a tranny rear tailshaft bearing go bad, same chatter resulted as I described. I looked at Autozone.com, but didn't even see this part he described.
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box
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Re: chatter vibration above 65mph, what is it?

Post by 1Gary »

Yeah that does kind of make sense given the rear seal issues too.If it was me,I would work a deal with a trans shop where I R & R the tranny and walked it threw their door to do their thing. :-k
1979 Malibu drag race only car
1999 Sonoma 4.3 5 speed-Rufus
1989 Astro-Ole Yellar cancelled-still selling off parts
1985 Astro-shop van R.I.P. my friend
1994 Astro LT RWD W4.3 rod knock RIP
1982 Winnebago single rear wheel-Chevy 350 Scraped 1/28/13-broken dreams......


Rochester,NY

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Re: chatter vibration above 65mph, what is it?

Post by astroturf »

U joints first...

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Re: chatter vibration above 65mph, what is it?

Post by LiftedAWDAstro »

I had a violent shaking in the SPB after the first 4" lift and it ended up being the tail shaft bushing was bad. No bearing in there. Pull the cone off and you can pound the bushing out and press a new one in as well as a new seal. It only happened between 55 and 65 mph.
Current rides:
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

Mileage spreadsheet

Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy

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Re: chatter vibration above 65mph, what is it?

Post by NotDadsW41 »

When you took the drive-shaft out, did you get it back in the same place? I seem to recall that if you don't get them back in the yoke in the same place they will vibrate. Take it out, rotate 180* and reinstall.
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Re: chatter vibration above 65mph, what is it?

Post by LiftedAWDAstro »

I have heard that too but I think it's a myth. The drive shafts are balanced on a machine and not in the vehicle. The machined parts in the tranny as well as axles and t-cases are all balanced by the way they are made. Plus the vibration was present before the drive shaft was pulled.
Current rides:
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

Mileage spreadsheet

Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy
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Re: chatter vibration above 65mph, what is it?

Post by LaGrasta »

Yes, from my expereince a drive shat can be reinserted anywhere within the spline, does not affect rotation balance.

I spoke with a professional mechanic friend of mine and he seems certain it's my rear wheel bearings. This coming weekend, we'll pull the axles and take a look. I'll report back…
1998 Astro, 246,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box
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