Yj with a aw4 tranny (vibrating in od) - JeepForum.com
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Unread 11-01-2013, 11:10 AM   #1
lbsickboy
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1986 YJ Wrangler 
 
Join Date: Aug 2011
Location: Den Haag, zuid holland
Posts: 190
Yj with a aw4 tranny (vibrating in od)

Hi all
recently i have swapped a jeep xj 4.0 motor en AW4 tranny over into my 87 yj,
it has a 4 incH lift kit with the 1.5inch shekels so a total 0f 5.5 inch lift.
The drive shaft front is made longer and the back is shorter
i have a sye kit with the cv drive shaft from the xj at the back,
the thing is when im driving on the highway in over drive the jeep vibrates doing about 50 mph not really bad but its very annoying, when i got to give gas it goes away when i speed increases.

also should mention the yj had A tf999 auto with a 4.2l,
so im thinking it might be the gear ratio, if im right it has the 3,55 gears.

any gear heads out there that can help out please

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http://www.jeepforum.com/forum/f12/4-0l-xj-97-motor-into-yj-87-a-1567705/
WANGLER 87 4.0 HO AW4
4,5 " ROUGH COUNTRY LIFT KIT, 1.5" BOOMERANG SHACKLES, 33'' BANDEN, ROUGH COUNTRY DUAL STEERING STABILIZER
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Unread 11-01-2013, 12:30 PM   #2
SeanB95YJ
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1995 YJ Wrangler 
 
Join Date: Nov 2009
Location: Schenectady, New York
Posts: 1,184
my first guess would be the rear driveshaft needs balancing (or REbalancing). sounds like you're just hitting it's "sweet spot" of RPMs for resonant vibes.
my second guess would be need of fine-tuning of the rear pinion angle
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[FONT="Comic Sans MS"][COLOR="Blue"]Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
[/COLOR] [COLOR="Red"]swap/build thread: [url]http://www.jeepforum.com/forum/f22/after-almost-4-years-finally-my-own-build-swap-thread-1542284/[/url][/COLOR][/FONT]
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Unread 11-01-2013, 01:42 PM   #3
lbsickboy
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1986 YJ Wrangler 
 
Join Date: Aug 2011
Location: Den Haag, zuid holland
Posts: 190
Quote:
Originally Posted by SeanB95YJ View Post
my first guess would be the rear driveshaft needs balancing (or REbalancing). sounds like you're just hitting it's "sweet spot" of RPMs for resonant vibes.
my second guess would be need of fine-tuning of the rear pinion angle
yes i was thinking about the drive shaft to it was balanced for me a mate of mine did it for me ill ask him to check it over.

the rear ring pinion was ok when i had the tf999 tranny in it.
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http://www.jeepforum.com/forum/f12/4-0l-xj-97-motor-into-yj-87-a-1567705/
WANGLER 87 4.0 HO AW4
4,5 " ROUGH COUNTRY LIFT KIT, 1.5" BOOMERANG SHACKLES, 33'' BANDEN, ROUGH COUNTRY DUAL STEERING STABILIZER
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Unread 11-01-2013, 02:10 PM   #4
lbsickboy
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1986 YJ Wrangler 
 
Join Date: Aug 2011
Location: Den Haag, zuid holland
Posts: 190
Just got of the phone with my mate that balanced the drive shafts,he said the back drive shaft is balanced to a piont where its 2 tenths of a millimeter thats 0.00787401575 inches.
so that's nothing for that length of my back drive shaft, its 40.5 cm lang.
so where else could i be getting the vibes from?
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http://www.jeepforum.com/forum/f12/4-0l-xj-97-motor-into-yj-87-a-1567705/
WANGLER 87 4.0 HO AW4
4,5 " ROUGH COUNTRY LIFT KIT, 1.5" BOOMERANG SHACKLES, 33'' BANDEN, ROUGH COUNTRY DUAL STEERING STABILIZER
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Unread 11-01-2013, 02:50 PM   #5
SeanB95YJ
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1995 YJ Wrangler 
 
Join Date: Nov 2009
Location: Schenectady, New York
Posts: 1,184
I wasn't talking about the ring & pinion gears... I was referring to the pinion ANGLE in relation to the transfer case output... the AW4 is a bit longer than the TF999 which changes the drive shaft/pinion angle slightly... and on top of that, you now have overdrive which changes the RPM relation between the engine and output so resonant vibrations that may have been absorbed or cancelled out before are now noticeable. you said when you give it gas it goes away.
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[FONT="Comic Sans MS"][COLOR="Blue"]Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
[/COLOR] [COLOR="Red"]swap/build thread: [url]http://www.jeepforum.com/forum/f22/after-almost-4-years-finally-my-own-build-swap-thread-1542284/[/url][/COLOR][/FONT]
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Unread 11-01-2013, 02:53 PM   #6
SeanB95YJ
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1995 YJ Wrangler 
 
Join Date: Nov 2009
Location: Schenectady, New York
Posts: 1,184
an old trick that couldn't hurt to try.... remove the driveshaft and drill a small hole in the rear tube and fill about 1/3 to 1/2 way with automatic transmission fluid, then weld the hole back up... the fluid inside acts as an additional balancer and will also help absorb resonant vibes.
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[FONT="Comic Sans MS"][COLOR="Blue"]Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
[/COLOR] [COLOR="Red"]swap/build thread: [url]http://www.jeepforum.com/forum/f22/after-almost-4-years-finally-my-own-build-swap-thread-1542284/[/url][/COLOR][/FONT]
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Unread 11-01-2013, 04:27 PM   #7
lbsickboy
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1986 YJ Wrangler 
 
Join Date: Aug 2011
Location: Den Haag, zuid holland
Posts: 190
OK im of to my mates tomorrow and see what we can do,thanks for the tip
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http://www.jeepforum.com/forum/f12/4-0l-xj-97-motor-into-yj-87-a-1567705/
WANGLER 87 4.0 HO AW4
4,5 " ROUGH COUNTRY LIFT KIT, 1.5" BOOMERANG SHACKLES, 33'' BANDEN, ROUGH COUNTRY DUAL STEERING STABILIZER
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