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death wobble still


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I have an 89 Comanche Sport truck that had a D35. I recently swapped in a D44 performing a SOA conversion. By cutting the spring perches and using XJ shackles i've got the rear lift about 4"...

 

I'm currently experiencing death wobble. And going though Idea as to the fix.

 

Transfercase drop or yj Yoke?

Or both??? anyone know typical at rest measurement for the slip yoke out of the cone?

Need to see if driveline is too short w/ 4" lift. I know the D44 Snout is 1" longer than D35 but yoke currently looks to be pulled an extra 1/2" assuming the shiny part was inside.

 

In the front i'm swapping in LCA that are adjustable, and the HD trac bar. but does anyone have an opinion if the knuckle to knuckle steering is better than the stock y? also have a 3/4" pitman arm drop should or should not use??

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with a 4" lift (driveshaft is now short an inch) and a Dana 44 (snout is 1" longer than a Dana 35) added to the mix, your rear shaft should be about the right length. don't forget to install new U-joints. old joints don't like changes in their operating angle and that can cause vibrations.

 

death wobble is a horrifyingly violent shaking of the front end that makes you slam the brakes and pray to god that you don't hit something. Is that what you're experiencing?

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You didn't say anything about the front axle.

 

My guess is that you did the SOA on the rears.....did you lift the front also?

 

If not then you have a castor issue causing your problem.

(Front wheels tilted too far forward)

 

The fix, lift the front or put more shims in the LCAs to get your 7* neg castor.

(knuckles tilted back 7*)

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If you did lift the front that may be the cause of it. Front lift pulles the inverted Y steering up, causing toe in. 4.5" front lift gave me 2" tow in, causing DW at speeds as low as 25mph, violently enough to fry my alternator bearings (as well as pop the front panel off the radio, , pop the sun visors out of the clips, throw the change out of the center console cubbies, pencils out of the cubby below the glove box, and fillings out of my teeth.)

 

Reset the toe at 0 and all was well.

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everything is tight new u-bolts, new shocks all arround. Just got new u-joints for the driveline, found out that only 1 bolt remained on the transfercase mount. frame appears to be rust free and solid. a bit of rust on driverside floor board that i need to address soon.

 

I did put what should be a 4" lift on the front but it only went up 2.5. Waiting for manufacture to warranty the springs that have less than 300 miles on them. plan to replace lca with adjustable ones. I have a pitman arm drop that's about .66" drop should i put that on? would changing from the Y design to the Knuckle to Knuckle be beneficial? Or would just changing control arms and getting an alignment possibly solve it?

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still need an answer for the length of exposed metal on the slip yoke on a stock setup. i'm going to post a pic from tom woods for measuring I'd like this measurement from a stock setup using d35 and 231 w/ swb. 231E_before_good.JPG

 

 

I'm thinking my driveline may actually be too long after the d44 conversion doing soa at same time. I calculate that had i done soa on the 35 my driveline would have needed to be 1/4" longer. but the d44 is 1" longer so excluding angles i'm .75 too long correct???

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All depends on pinion angle. I run a SOA 8.25", which is 1" longer than the stock D35 was, with re-arched springs (1" higher than stock), lift shackles (another ~.75" lift), and a YJ yoke for another 0.5" length.

 

Total lift over stock is ~7".

 

Between the slip yoke and nose of the pumpkin I have an extra 1.5" length. Perfect length drive shaft is ANOTHER 1" longer yet. I highly doubt 4" lift only requires a 0.25" longer drive shaft if ~7" can use 2.5".

 

I think you will be fine.

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still need an answer for the length of exposed metal on the slip yoke on a stock setup. i'm going to post a pic from tom woods for measuring I'd like this measurement from a stock setup using d35 and 231 w/ swb. 231E_before_good.JPG

 

 

I'm thinking my driveline may actually be too long after the d44 conversion doing soa at same time. I calculate that had i done soa on the 35 my driveline would have needed to be 1/4" longer. but the d44 is 1" longer so excluding angles i'm .75 too long correct???

 

SOA will drop your yoke 4 or more inches from stock and be 1 inch in...if you do the geometry, I believe it will be a wash.

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Got my stuff in to fix the front end issues hopefully.

 

 

Lets see... They put all this and more on in an hour on the TV show trucks, so i figure taking away all the time they spend talking about themselves... I'll have it done in 2 weeks. and yes that is a bottle of crown. I like good stuff while working on the car. Good by death shake in the truck...

 

64441_1552129397805_1072232659_1488768_7691783_n.jpg

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  • 2 weeks later...

HELP!!!!! Death wobble didn't go away need ideas!!!!

 

 

New control arms, Trac Bar, 4" lift (spring and spacer), new stabilizer, sway bar disconnects. I've done everything i can think of. Got an alignment. but...

 

 

at 55-65 i start to shake, not as violently as before the control arms and alignment, but still of concern. I'm going to check my wheel balance tomorrow. Any idea???

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The biggest cause of death wobble is the track bar being loose at one end or the other. the second is that the track bar and tie rods are no longer aligned due to lifting the truck, but this normally just results in bump steer.

 

J B Cuz

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The biggest cause of death wobble is the track bar being loose at one end or the other. the second is that the track bar and tie rods are no longer aligned due to lifting the truck, but this normally just results in bump steer. J B Cuz

 

Yes, JB, but he already replaced his track bar (see picture above), so he eliminated that cause. The only thing left to do is balancing, as far as I can see. :cheers:

 

-Tom

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I am not seeing new UCAs in that pic. Are you still running stockers?

 

I also see a CRusty's track bar. Take that POS and throw it as far as you can.

 

I fought DW on my WJ for over a month after I put a new CRusty's lift on it. It turned out to be the bushings were too soft in the TB. I put a Rock Krawler TB in it and it cured the DW.

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