91 300ZX TT 5sp Rear end grind at low speed help!!!

[The Vandal King]

I cannot figure where this is coming from. What I know so far, it only happens after driving for about 20 miles, some spirited driving. If the car sits and cools off for a few hours it goes away but eventually comes back. There is a rubbing/grinding sound only while turning and in gear from about 35-75 degree wheel turn, left or right. After 15 mph there is no "grind" while in a turn. If I coast in neutral the "grind" is not present.

History, Only owned the car a few weeks only noticed the grind after driving the car home (2hour ride)...I have since had the 120k service completed and a tune up, also the front tension rods replaced. I also had the rear pinion seal replaced and had the shop do a differential fluid flush. The idea behind the flush was that maybe the wrong weight of fluid was put in the diff. We thought it could be the rear axle bearings, but up on a lift showed no signs of this. The CV boots all are intact. The only thing I can think of is the HIKAS acting up? or something really wrong the differential. I am just scratching my head on this one.

The car has some mods that I found out after the fact, it is running a JWT ECU POP Charger with dual intakes and custom 2.5in cat back exhaust. s-afc is installed as well, from what read, this is a very reasonable set-up. Car is running 13.5psi per the ecu installed. But none of that screams that's where the grind noise is. And with it only doing this after extending driving and in gear, I'm unable to set it up some I can hear it in my garage..


edit:: Thanks for any help, even if it's use the search, problem with search is that grind is such a general term, that I have read everything from xmission questions to body work...

[centralcoaster33]

First thing that comes to mind is wheel bearings... the front ones actually. But check them all. Carrier bearings next (might be visibly diagnosed with the cover off) then CV joints (I'm not sure how to inspect without removal). Is there a chance this is your transmission, certain gears only perhaps? Third gets a lot of abuse. Those would be my suspects. Do you know what kind of differential you have in the pumpkin? Did you run the car in gear and have the wheels going while on the lift or were you just moving things by hand?

[centralcoaster33]

Oh, and welcome to the Forums!

[The Vandal King]

Thanks, checked axle bearings, but not the carrier bearings and xbox joints. Thanks for the welcome and reply

[The Vandal King]

So LSD is where the sound is coming from. Probably bad vicous, need to find a good low mile Lsd...Thanks for the help anyway.

[DCaff300ZX]

I see you mention a culprit, but just for the heck of it check the brake dust/debris shields which also can become close enough to the rotors to touch during turns, and also trap small rocks which can cause grinding and other noises. Have had both in my 14 years of Z32 driving.
Another possibility but only after collision damage or adjustable rear suspension upper control arms is the HICAS connector contacting the inside of the rear wheel/rim during turns, but without adjustable RUCAs out of adjustment range and showing extreme camber, only can happen with bent HICAS arm or bad HICAS arm ball joints. All worthy of inspection/consideration.

[The Vandal King]

I see you mention a culprit, but just for the heck of it check the brake dust/debris shields which also can become close enough to the rotors to touch during turns, and also trap small rocks which can cause grinding and other noises. Have had both in my 14 years of Z32 driving.
Another possibility but only after collision damage or adjustable rear suspension upper control arms is the HICAS connector contacting the inside of the rear wheel/rim during turns, but without adjustable RUCAs out of adjustment range and showing extreme camber, only can happen with bent HICAS arm or bad HICAS arm ball joints. All worthy of inspection/consideration.

Yeah, I had to have the Rotors turned until I can get enough money to replace them, but we went through the entire brake system. We had the car on the lift and everything sounds fine, it's just during quarter turning you can hear what we think is the viscous coupler failing. The HICAS looks and seems to be running fine. We checked for loose control arms, and checked the camber, I need to adjust the camber a tad, but it's not crazy out of whack right now.

The hardest part is waiting on a good LSD to come up, doesn't seem like there are many of these LSD's left over. I want to check to see if any other LSD's would work, might be worth a shot.

[DCaff300ZX]

Too bad not a Wash. state guy, we have lots of Z32 stuff and partouts around all the time. I even have a NA with AT lsd (4.11 gear) in my old NA I'd let you pull and sell you if you were from around here, but not looking to do it myself or ship it.
Look for NA/AT partouts (most common Z32) and you get the benefit of a little more acceleration from that lsd.

[The Vandal King]

I have found two TT VLSD's near me, wondering how difficult the swap is. I am currently searching as I cannot keep the car in the garage past a weekend. Part is
running around 350.00, the labor was quoted as 500.00.

The other option is a Tomei LSD, but I can't seem to find any reviews or experiences with that upgrade on a TT. I am running a little over 400hp.

[DCaff300ZX]

The swap isn't too tough beyond the larger parts and supporting the subframe, etc., I haven't tackled it myself but did look into it a bit when deciding whether to ditch my HICAS (kept it). I believe that if just swapping diff's it's not worse than swapping parts, but I'd look for a how-to on tt.net or robo's site just to be sure and have detailed info/strategy.
Good Luck!