tiredandwired

I recently had the 3 u-joints replaced on my '95 Tacoma AT, by a mechanic who told me it was within his skill and comfort level. Symptoms included an intermittent loud clatter upon acceleration. I took it in immediately.

My mechanic replaced the u-joints, had to rebuild the double cardan joint and though the clatter went away, It was replaced by a muted "thunk, thunk, thunk" upon accelerating from stop and a lot of vibration at all times.

My mechanic took the driveshaft in to be balanced and they could not balance it. They did, however, have a used driveshaft there that balanced out, was equal in every other way, except that it was 1/4" too long. But, they said that if it fits, it will work.

Well, it fit fine, according to my mechanic, ( I have a slight lift on my truck because of an extra leaf spring), but when I drove away, lots of vibration and the same thunking sound upon initial acceleration. This driveshaft was balanced. Neither the vibrating nor the thunking were issues before the u-joint work so all symptoms assumed to be related to all that has been done at this point..

My questions:

-Will a new driveshaft likely solved these issues?

-Did my mechanic screw something else up when he did this work? ( He's a good guy and will do what's right I think, but is not taking responsibility at this point)

-Can I drive this for a few days around town with these symptoms until I get this figured out?
Any/all info. greatly appreciated~

Maggie

Maj

I'm wondering what your wrench did to your original drive shaft that made it un-balanceable. Him not taking responsibility is another bad sign. The 1/4" longer drive shaft might become an issue on full suspension compression. If the slip yoke bottoms out that will place a lot of stress on you pinion and rear transmission bearing.

I suggest you take your truck to the place that did the drive shaft balancing and let them take a look at it. They will hopefully have the expertise to figure out the problem. I would then make your original mechanic refund at least part of his fee.

Unless the vibration is really horrendous it won't hurt to drive it short distances for a couple of days. Stay away from high speeds.

The rear transmission mount should be checked. That can cause vibrations.

tiredandwired

Thanks so much.

Machine Services did the balancing on this slightly longer drive shaft and said it balanced out. They also put on new u joints, so technically, everything checked out on this one.

Could the issues be related to the slightly longer shaft ( vibration, muffled thunking at the onset of acceleration same issues I had with old shaft that wouldn't balance), or is there something else going on? I think my mechanic got in over his head with rebuilding the double cardan, but is there some trick to bolting on the driveshaft that he is missing?

Maj

I'm not familiar with the Taco setup but you typically scribe marks on adjoining parts prior to removing the drive shaft so that it is reinstalled in phase and balance from the factory. Since you have a non OEM shaft then the mechanic should have removed any yokes or flanges on the t-case and diff that were to be reused and had them balanced with the replacement shaft. If the mechanic separated the slip yoke and didn't properly "clock" the parts when installing then that could cause problems.

The longer shaft shouldn't be an issue except on full suspension compression. Your Taco probably has the center support bearing-style drive shaft and that bearing along with the tranny mount should be checked. Don't waste your time taking it back to the mechanic. He has proven he doesn't know how to make the proper fix.

tiredandwired

Thanks! I don't believe I have the enter support bearing. The drive shaft is from a Toyota truck, they just were not sure which year. They will rebalance it again tomorrow. They said they are always balanced with the flanges.

Do I have to worry so much about full suspension compression since I had a 4 leaf spring pak put in rather than the 3 leaf, which this truck typically takes, so that we could haul wood and compost.

I likely will need to have this mechanic put it back on if I'm ever going to have a case for a refund...Is there anything else that he could have damaged or misaligned when he took it off initially to replace the u-joints? Since the initial work, it developed a muffled "thunk, thunk, thunk," when I first accelerate from a stop while in gear. It is on;y momentary~

Maggie