Deep noise during initial acceleration (5spd Terrano)

[danielbeek]

Hi,
for quite a while now (maybe 1.5-2 years) I've had a worrying noise coming from somewhere underneath the old Terrano.
It's a '95, had zero offroad time when issue first appeared, has a 5 speed box, TD27T, and an 4.8 ratio rear LSD diff (which I put in). I think issue predated diff install, but not sure. Vehicle also has about 2" sus lift. About 240ks, and I think original clutch.
So far I've only noticed issue when accelerating moderately hard from stationary - wheels straight ahead (not the steering stop issue). It stops making noise within what seems a second or two.
The sounds is a deep dry thump/thud (one or a few in short succession), combined with a deep groan (! ). It sounds like it could be coming from anywhere from the gearbox, to back to the rear diff.
The whole thing sounds like there's a lot of weight or force behind it. I don't think it's something like the exhaust knocking the body as I've checked it over, and the sound seems to 'heavy' to me and is definitely not rattly or metallic in any way. I think engine mounts are ok too.

I've recently read about very similar sounding issues on other vehicles relating to the clutch thrust bearing. Also saw something about issues with slip joint (?) in the main drive (prop) shaft on raised vehicles, and wondered if lack of lube could cause binding as the driveline is loaded up and it tries to adjust length.

Early on I recall also noticing it felt like a little lag/flat spot in acceleration (without the noises), a very short moment after hoofing accelerator and vehicle had already started picking up speed. Like sudden but short lived clutch slip. Strange as clutch seemed to already have 100% 'bitten'......
Also only at initial take off, not at speed as far as I can tell.

Anybody know this one, or have a good idea of likely culprit?

[nizute]

i would check your driveshaft hanger bearing if it has one.

[lax2wlg]

Hi Mate. Worn Clutch release bearing should be a constant noise that disappears when clutch is pressed in. But shouldn't cause 'driveability' issues as such

With my old setup I was getting similar symptoms to what you have described. Regreased the rear driveshaft UJs. Also added a little grease to the splines on the slip joint.I thought they were sealed for life, but slide Nathan told me that there is an access screw for servicing They've probably never been serviced.


I thought my old g/box bearings were on the way out, it was just dry UJ slop!

[nzlux]

My guess is hanger bearing or drive shaft universal joints.
If you get under your truck and give the drive shafts a shake it will let you know what is loose.

[zukmeista]

A thud could be worn bushes at diff end allowing it to rotate slightly?

[danielbeek]

Thanks for the helpful suggestions guys, will look in to these and report findings. Good to hear it's similar to issue you resolved Josh. Zukmeista, interesting point about the TA bushes to diff. They looked good condition, but I wonder if I possibly under torqued them when the LSD diff went in, and when accelerating the inner collar is turning/creaking when it should stay put.

[hamboy]

I had a similar noise in mine a while back, turned out to be the front cross-member, the bolts had stretched slightly allowing a small amount of movement. It got worse over time and started doing it while turning in my driveway. I only happened to find it when I jacked the front up to check the steering

[ChurchurDan]

Check your gearbox mount as well.

[danielbeek]

Well, finally case closed.
It was the exhaust all along...
Aftermarket Autobend system. Clearance was fine, but one of the studs on the 3-way flange from manifold to down pipe had sheared off. Probably due to the missing nut on other stud.
So thudding must have been it opening/closing as engine movement twisted it open, and loud deep 'groan' as the exhaust vented direct in to engine bay....
Lesson learnt: pays to check the easy stuff first.