Front Driveline Vibration

[4.0literstofreedom]

I have been living with a vibration on my TJ that starts around 60 mph and gets obnoxious above 68 mph. Today I pulled my front driveshaft and was pleasantly surprised to find the vibration went away!
The problem started after I had some axle work done at a local shop. I had the Dana 35 replaced with a Ford 8.8, along with a SYE and Adams driveshaft out back. I had the Dana 30 regeared to 4.10 to match the gears that came in the 8.8 and a sleeve and gusset kit from Synergy Mfg was installed.
I initially thought my rear pinion angle was the issue, so I got some adjustable UCA and got the pinion angle to within about a degree of driveshaft, but the vibration didn’t change.
Right now I am suspicious the new gears in the front axle were not set up properly. There is about 1/8 turn of slack (backlash?) in the ring and pinion, and about 1/16” slack when I pull back on the yoke. I’m not an axle setup guru so I don’t know if this is unreasonable.
Is there anything else that I should look into?
Thanks,
Sloan

 

[Jerry Bransford]

That amount of backlash is normal, that amount of in-out slop on the front pinion shaft is not. Either the pinion nut loosened up on you or either the inner or outer bearing has gone bad.

 

[bobthetj03]

It's acceptable to have some rotational play in the yoke, but you should have zero play in/out or side to side. What does your front pinion angle look like compared to ds angle?

 

[4.0literstofreedom]

That amount of backlash is normal, that amount of in-out slop on the front pinion shaft is not. Either the pinion nut loosened up on you or either the inner or outer bearing has gone bad.

Will tightening the pinion nut a little bit throw off any of the other gear adjustments? I’m wondering if I should try that in my driveway, or just take it back to the shop that did the work. I’m hoping the bearings are ok, I don’t have any leaks or noises after several thousand miles of driving with it like this.

 

[bobthetj03]

I'd take it back to the shop and tell them to make it right.

 

[4.0literstofreedom]

It's acceptable to have some rotational play in the yoke, but you should have zero play in/out or side to side. What does your front pinion angle look like compared to ds angle?

The front driveshaft angle is several degrees steeper than the pinion, still running stock UCA’s with 170k miles on 3” lift and 33” tires. I ran the same DS angle for several thousand miles before the regear and didn’t have a problem, but I am spinning about 500 rpm higher now at high speeds.

 

[bobthetj03]

I understand your plight. I re-geared from 3.73's to 4.56's and instantly had drive line vibes with the only change was the re-gear. After throwing a lot of time and money at the problem I found that my TJ is just really sensitive to change. I haven't completely eliminated my vibes, but I have now where it is acceptable for me. Get adjustable arms and get the pinion angle closer to the DS angle. Lowering the t-case, or adding a MML will help with this as well. Matter of fact, as an experiment, lower the t-case skid 1/2' at a time and test drive. See if you feel any improvement at each lowering.

 

[LieutenantJohnson]

Will tightening the pinion nut a little bit throw off any of the other gear adjustments? I’m wondering if I should try that in my driveway, or just take it back to the shop that did the work. I’m hoping the bearings are ok, I don’t have any leaks or noises after several thousand miles of driving with it like this.

Edit:

Though I too would take it back to the shop that did the work... I would also just try tightening the pinion nut down, as it may have backed off slightly. HP30s do NOT use crush sleeve, but LP30s do use a crush sleeve. So do not go hulk on it. See if it is loose.

 

[bobthetj03]

Though I too would take it back to the shop that did the work... I would also just try tightening the pinion nut down, as it may have backed off slightly. It is NOT a crush sleeve, so you won't hurt anything. Should be pretty simple, especially if the front shaft is still out

My Dana 30 had a crush sleeve.

 

[LieutenantJohnson]

My Dana 30 had a crush sleeve.

Yes I just edited my post. Thanks for the correction.

I am so used to HP30s (last TJ swapped it in) and rubi 44s that do NOT use crush sleeves. I would still check to see if nut is loose

 

[Goatman]

I doubt adjusting the trans drop will cure a FRONT driveline issue. Actually it would be increasing the front driveline angle worsening the vibe issue.

 

[4.0literstofreedom]

I ran with a 1” trans drop for awhile and it didn’t seem to make any difference. When I got my adjustable rear UCA’s and dialed in the rear pinion angle I ran with and without them and it didn’t make a difference, so I left them out for the extra clearance.
I’m about to check and see if the pinion nut is really loose, if not I’m taking back to the shop and see what they say.

 

[EzPeezy]

Whether it's loose or not you need to talk to the shop to make sure it's right. It's not hard for them to check the torque on the pinion nut. Call and tell them the problem and if they're a good shop they'll tell you to come in for a check-up.

 

[4.0literstofreedom]

Just got back from taking the Jeep to the shop that did the gears. They said everything looked fine with the front ring and pinion and the driveshaft is likely the problem. They didnt open the diff cover and the guy told me Dana 30’s in TJ’s don’t have crush sleeves. He said everything is adjusted by shims, and if it was out of adjustment the seals would be blown. I told him that low pinion Dana 30’s do have crush sleeves and he didn’t believe me. I have had my doubts about this shop, so i’ll likely take it somewhere else for another opinion.

 

[tworley]

[QUOTE="4.0literstofreedom, post: 494631, They didnt open the diff cover and the guy told me Dana 30’s in TJ’s don’t have crush sleeves. He said everything is adjusted by shims, and if it was out of adjustment the seals would be blown.... so i’ll likely take it somewhere else for another opinion.
[/QUOTE]


Good call. That mechanic is clueless

 

[4.0literstofreedom]

While the explanation given by the new guy working the front desk at the shop was totally bogus, I think the take home point was the guys in the back didn't think the torque on the pinion nut was out of spec. They thought the front driveshaft (still original after 170k) was more suspect and recommended replacing with a new one from Adams. I'm going to give it a shot and go from there. If anything, it was about due to be rebuilt or replaced, and it helps with the process of elimination for the driveline vibe.

 

[Apparition]

Just got back from taking the Jeep to the shop that did the gears. They said everything looked fine with the front ring and pinion and the driveshaft is likely the problem. They didnt open the diff cover and the guy told me Dana 30’s in TJ’s don’t have crush sleeves. He said everything is adjusted by shims, and if it was out of adjustment the seals would be blown. I told him that low pinion Dana 30’s do have crush sleeves and he didn’t believe me. I have had my doubts about this shop, so i’ll likely take it somewhere else for another opinion.

My 30 definitely had a crush sleeve. I had a hell of a time with a sleeve that wouldn't crush until I bought another sleeve.

 

[4.0literstofreedom]

I got my new Adams driveshaft installed today and drove 75 mph with no vibrations. It was amazing. The stock driveshaft had a little play in the joint that slides back and forth. I think the reason I didn’t notice the vibration before the regear was I was spinning several hindered rpm lower on the highway than I am now.