Hey guys! it's been awhile but I was wondering if anybody has experienced Grinding/hard clicking/Clacking during heavy acceleration from the rear or trans tunnel area? to me It sounds a lot like the rear axle splines are worn out and or skipping when accelerating hard from a dead stop. Cruising down the street or freeway is normal with no gear noise/whine at all.

The car-1990 coupe ZF 6-speed, bought 97,000mi Aug 2009, superram, otherwise stock engine, GS size wheels, Spec stage 2 kevlar clutch, lighten steel single mass fly wheel (done in 2010) and just finished up a complete urethane bushing kit and ball joints, VB&P heim joint rear adjustable toe links and replaced all U-joints.

Current mileage 111,xxxmi One recent track event at Laguna Seca (Feb 2014) finished off an axle u joint when done, lol (fixed) Last weekend I checked the total back lash by lifting the rear end up and when left in second gear I only have about a half inch of back lash at the tire tread (not too bad I think). The LSD has an initial torque somewhere north of 100 LB ft, I can torque my wheels without diff action. I would estimate the break away torque value to be around 150 Lbs as I can turn the LSD by hand and get diff action if I'm quick at turning the rear wheel fast the LSD feels smooth with no chatter. I did notice the right rear wheel axle did squeak when checking the back lash so I'm hoping it the Rear axle wheel bearing assembly and drive yoke splines are worn out...the cheapest fix compared to diff and trans repair cost.

I've searched the forum and it seems the general consensus is the rear hubs and axle yokes are the weakest link in a ZF6 Dana 44 combo, what are your thoughts? If it turns out to be the wheel bearing assembly and axle yoke what are good replacements? Moog or Timken? I'm having some trouble sourcing rear drive axle yokes.

Thanks in advance!

 

You may have the same issue as I am experiencing now. Mine has been clicking for a couple of months and thought it was a u joint. Yesterday coming home I kept smelling 90wt and look under the car to discover the yoke seal is leaking. I think the yoke bearing has gone south but dont know if it and the seal can be replaced with the rear end in the car.

 

I just recently replaced all my U-joint because I broke one or finished one off during my Laguna Seca HPDEvent. That was a squeaking/creaking sound under light loads and a noticeable clunk under a hard launch with a random vibration on the freeway. I some how managed to turn all the needle bearings in one bearing cup turn into dust. I doubt the seal or any diff repairs can be done while the diff is still in the car. I'm not leaking any gear oil but my issue could very well be diff side gear splines

I was really hoping it was the stub axle/rear wheel hub splines...I did a quick test drive just now and heard the clicking / grinding sound while under half throttle, 1st gear over 150 ft or so...definitely the diff or ZF6 trans I painted indexing marks on the stub axle shaft and the hub on both rear wheels and they are still perfectly in line

The next step is to drain both fluids and inspect for metal flakes

Now, what are the common wear issues in the ZF6 trans and the Dana 44 Diff? What options are available when rebuilding ZF6 and or Dana 44's? Upgrades? Estimated cost?

 

Newark, CA?
You're in my neck of the woods!

I had the same exact problem with my '95 six speed. Knew exactly what it was and I took it to a place called Rearend Specialties in Santa Clara. Had them change the rearend fluid and added two (not one) of the GM rearend supplement as instructed by forum members and it was instantly like new when I drove it home. Been that way for the last six years now and had forgotten about it until I saw your post.

Been going to these guys for decades...they are great for rearend gear ratio changes too. I do a ton of my own work, but when it comes to rearends, I prefer these guys.

http://www.rearendspecialties.com/

 

Yep, near the dumbarton bridge! Thanks for the info, I will follow up with these guys if when I find out the diff is the problem. My issue mainly happens in 1st, 2nd, and 3rd gear. I was late for work one day and I was running through the gears and heard the grind/skipping in the rear or center of the car every time I let the clutch out and get back on the power (Not from a miss shift), and then again on a hard accel from a roll. I can always repeat the sound if I kick the clutch in any gear...which leads me to believe this is a diff problem

What was wrong on your '95? I would guess diff chatter. Unfortunately I doubt and I wish it could be fixed by a simple fluid change...this sound is a pretty loud click/grind that can be felt through out the car.

I just a had a random thought...If the diff posi clutch pack is heavily worn, would that allow the diff side gears to move further away and allow the diff spider gears to skip past on another?

 

Thanks...I'm no expert on differentials, but mine was certainly louder than the chatter I've heard on my '68 Camaro years ago, more like a knock. Definitely not a grind though. Those guys are real good...great to know a place that actually specializes in one thing and does it well. The collection of failed rearend parts on display (some went spectacularly!) in the waiting room is hilarious too.

Love that shot of your car on the corkscrew at Laguna Seca...my favorite track of all-time. I used to go there with GGLC all the time.

Hope you get her resolved real soon!