Help! New gear noise....

Submitted: Wednesday, Jun 21, 2006 at 16:41
ThreadID: 35147 Views:1848 Replies:5 FollowUps:4
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Hello Forumites,

Im calling on your collective wisdom. Let me set the scenario...
What's the rig?
An FJ40 SWB with a Holden 308, running stock 4speed gearbox and solid transfer case.

What's happened?
1) The gearbox and transfer were recod'd. Only new parts were the main shaft out of the gearbox, and the transfer case input gear.
2) The gearbox was re-fitted and I noticed a new noise which was not there prior to the reco. It was a rumbling noise which only appeared in four wheel drive, both with the hubs locked and unlocked.
3) Took my rig back to the mob who reco'd the box and trannie, and after much deliberation, they determined it was the front diff.
4) The front diff was overhauled by the same mob, it's as tight as it will ever get.
5) The rumble is still there
6) The transfer has since been pulled down again completely, however there was nothing apprent which could be causing the noise.

As such Im seeking the advice of anyone and everyone....What could this be?!?!

The rumble is very obvious (makes me grimace). It is present in both four high and four low. When the hubs are locked, it is there under deceleration. When the hubs are unlocked, it is there under both acceleration and decelleration.

I appreciate any comments!!
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Reply By: Turist - Wednesday, Jun 21, 2006 at 17:01

Wednesday, Jun 21, 2006 at 17:01
Just a silly thought is the problem in the gears or could it be something else in drive train eg. wheel bearings etc?
AnswerID: 179694

Reply By: Peter 2 - Wednesday, Jun 21, 2006 at 17:55

Wednesday, Jun 21, 2006 at 17:55
Check tailshaft uni's and driveline angles, the uni's are best run at a slight angle rather than straight.
On an older vehicle it can also be the tailshaft sliding splines slightly worn too.
AnswerID: 179708

Reply By: Mikee5 (QLD) - Wednesday, Jun 21, 2006 at 18:01

Wednesday, Jun 21, 2006 at 18:01
When you engage 4WD a sleeve is pushed over a spline in the extension housing on the front of the t/case. This connects the front drive to the rest of the transmission. In the front extension to the transfer I think there is an adjustable bearing. Was this extension checked, was it over tightened - there is a big nut under where the front drive shaft bolts on. Are these bearings worn. I am only thinking that this part is suspect because the noise only happens in 4WD. Did you really put it in 4WD with the hubs unlocked?
I have owned and recond both an FJ40 and an HJ45 t/case. Good luck.
AnswerID: 179711

Follow Up By: Member - MUZBRY VIC) - Thursday, Jun 22, 2006 at 09:30

Thursday, Jun 22, 2006 at 09:30
Is there a problem driving with the vehicle in 4wd and the hubs not locked in?
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FollowupID: 436004

Reply By: fateddie54 - Wednesday, Jun 21, 2006 at 19:10

Wednesday, Jun 21, 2006 at 19:10
Thanks to all for your responses so far. Here's a little more info:

1) During the reco of the front diff, the entire front-end was inspected and replaced as necessary. ie wheel bearings, swivel pins etc.
2) When the box and transfer were reco'd all bearings, shafts, shims, gears etc were inspected and replaced if out of tolerance.
3) The noise was not present prior to the reco, so I do not expect the noise to be a result of uni's?????
4) A lot of thought did go into the preload on the tapered bearings in the transfer, which was checked, and re-checked, and re-checked.
5) The mob doing the work is 100% confident that it is nothing forward/rearward of the gearbox/transfer.

I think I can feel the same rumble, although subtle, when in 2WD. However there is some scepticism about this theory, as the amount of load going through the gearbox doesnt change a great deal when 4WD is engaged (the gearbox is still driving the same mass, it's just split front and back). Which leads to the thought that if the noise was from the gearbox, it would be just as prominent in 2WD as in 4WD.

By the way, Im not trying to shoot anyone's ideas down here. Just putting the info out there to help understand the problem!
Thanks to all for your thoughts so far....I look forward to some more!
(Yes I did drive in 4WD without the hubs locked briefly, to test for any alternative symptons...)
AnswerID: 179737

Reply By: Mikee5 (QLD) - Thursday, Jun 22, 2006 at 17:56

Thursday, Jun 22, 2006 at 17:56
A suggestion is to unbolt the front shaft from the t/case and diff , undo the front hubs and drive around. Stop and turn engine off to avoid damage, engage 4WD and drive around again. Listen for your rumble. Repaet with hubs done up. This may or may not help to track it down.
AnswerID: 179921

Follow Up By: Mikee5 (QLD) - Thursday, Jun 22, 2006 at 19:38

Thursday, Jun 22, 2006 at 19:38
Another thought is this - how much grease was pumped into the spline on the front shaft. If there is too much you can get a binding effect which can be felt through the transmission.
FollowupID: 436122

Follow Up By: fateddie54 - Thursday, Jun 22, 2006 at 20:14

Thursday, Jun 22, 2006 at 20:14
Thanks for the suggestion Mikee5. When I get my hands back on the girl next week I'll give this a try!
I am aware of the trouble too much grease can cause. But again this noise wasnt present prior to the rebuild so Im confident the trouble is not with the front shaft. Thanks for the thought though! :-)
FollowupID: 436128

Follow Up By: Member - Barry C (NT) - Thursday, Jun 22, 2006 at 23:40

Thursday, Jun 22, 2006 at 23:40
I note you said bearings and other parts were replaced if worn or out of tolerance.
I suggest that if the main shaft bearings were not replaced this can cause problems and I agree with Mikee5's advice above.

Also check the driveshaft alignment (ie universals in line and not one spline out). Another thread a couple of months ago on a 100 series if I recall had the front driveshaft fitted back to front by dealer (just what you would like eh???)

General advice when overhauling gearboxes etc replace key parts.

Hope you track it down and it doesn't turn out to too expensive, sometimes the little things get overlooked.

Cheers Barry
FollowupID: 436169

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