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Tim Smith
02-14-2007, 03:45 PM
So we are going through this northeaster right now and I just had to take my 88" to work today (arm twisted :p).

With the roads so bad, I had to leave it in four-wheel drive while keeping it in a controlled slide most of the way to the office.

Then all of a sudden there was a thunk. A loud thunk. A thunk that sounded like a hammer against one of the gears in the transfer case. It occurs once every 200 feet or so and only when going above 25 mph while the engine was under load going up hill (but not down hill). Also, if going up a steep hill at speed the rear end felt like it was kicking out a bit right when the thunk happened. As if the rear end had just stopped momentarily.

It didn't happen under full lock in the covered parking garage at work but the truck did hop a bit as it should. So I know four wheel is working and that pressure build up in the transfer case doesn't make that sound at low speeds.

Any ideas? I'm thinking that it's a bad gear in the rear end transferring the pressure into the transfer case but only after a momentary lockup of the rear wheels.

Cheers,
Tim

KingSlug
02-14-2007, 04:17 PM
I had it happen once, chipped 2 ring gear teeth. I would bet its the back.

Tim Smith
02-14-2007, 04:25 PM
I had it happen once, chipped 2 ring gear teeth. I would bet its the back.

Thanks KingSlug. Do you mean that it was caused by two chipped ring gear teeth or that it, being the thunk, caused the chipped teeth? I'm guessing the former but wouldn't the truck do it in 2 wheel drive? Assuming it's the rear that is.

Dang I'm hoping to make it to Maine this weekend... a 7 hour drive. I assume this wouldn't be wise with a messed up rear end.
:mad:

KingSlug
02-14-2007, 04:52 PM
Ring gears can break just like axles, mine sounded worst at slow speeds because the pinoin wouldnt coast across the 2 bad teeth like it would at higher speeds. I would get a tow home or swapout the rear at work, it would suck if you lost more teeth, damaged your pinions and broke an axle. If the chips havent cause much damage just pull the third member and swap in another and you are off to Maine. You can do it in 30 minutes if you have a garage, lying on your back in the snow give it an hour.

Tim Smith
02-14-2007, 05:04 PM
Ring gears can break just like axles, mine sounded worst at slow speeds because the pinoin wouldnt coast across the 2 bad teeth like it would at higher speeds. I would get a tow home or swapout the rear at work, it would suck if you lost more teeth, damaged your pinions and broke an axle. If the chips havent cause much damage just pull the third member and swap in another and you are off to Maine. You can do it in 30 minutes if you have a garage, lying on your back in the snow give it an hour.

Unwittingly I drove it home already so no tow needed. Lucky!

If I had another diff I'd surely swap it out. Since I don't have one I think I might be stuck missing the Romp this year.

I'll have to do some more testing because I really don't want to miss it. Thanks for your advice though. You may have just saved me a huge bit of aggravation.

Tim Smith
02-14-2007, 06:16 PM
Okay, so I just did a test drive in 2wd with the front hubs locked and there is no thunk. By the way, I usually have the front hubs unlocked.

Could this be the front diff? Although the rear has been making some whirring noise since I installed it (used) more than a year ago, this particular problem has never cropped up till now. I've also never driven past 25 mph in 4x4 so I'm dealing with two firsts here.

Is there anything else that happens in a series truck in 4wd at road speeds that could be causing this?

Tim Smith
02-14-2007, 06:30 PM
Okay, just tried it in 4wd locked hubs and then unlocked. When locked I get the thunk, unlocked no thunk.

So it's the front diff then, right?

Mercedesrover
02-15-2007, 04:11 AM
Sounds like your drivetrain is getting loaded up and releasing. Are the tires all the same size? Are they worn the same? I really don't think you have anything to worry about.

If you had a broken ring gear you'd get a clunk with every rotation of the tires.


Jim

Clive
02-15-2007, 06:50 AM
A friend's truck had a thunk transmitted through the drive train when his free wheeling hubs went west....just a thought.

Tim Smith
02-15-2007, 08:51 AM
Thanks Jim. I think you are on to something. Since I've never had the truck in 4wd at speed, I guess I was bound to learn something new about the truck. It just sounded terrible!

2wd was fine this morning, so either way I'm going to ME this weekend. Keep an eye out for a stranded lightweight. :p

---

Clive. I swear, if it's these dang front hubs acting up again then they are going into the trash heap! :eek: I've spent enough time on them that they had better be working right by now.

runabout
09-02-2007, 01:24 PM
"Note: Driving in four wheel drive on pavement can be damaging to the drive train. On pavement, the wheels cannot slip and adjust themselves, so you will "wind up" the drive train until it breaks."


I saw this comment on the landrover FAQ site and it got me thinking. I want to use the 1973 series III for winter driving when the snow is too deep for the Volvo, as well as getting back and forth to the ski hill. What is the best advice here. Shall I stick to offroad 4 wheel drive? Thanks.

LaneRover
09-02-2007, 08:37 PM
When I drive my Rover in the snow I usually leave the front hubs locked but keep it in 2 wheel drive. If it gets real thick I then let off on the gas to make sure the rear wheels aren't spinning and then put it into 4 high. My feeling is that if you can go more than 25 mph do you really need it in 4 high?

If you were driving down the road in 4 wheel drive and it was only raining, I would think that there is a good chance that the big thunk was the drivetrain was releasing pressure as was mentioned earlier - I would still check for some damage.

And one thing I tell friends who go from San Diego or LA to a place with snow and they have a 4 wheel drive, "Just because you can go faster doesn't mean you can stop any faster"

Brent

Tim Smith
09-05-2007, 09:49 AM
"Note: Driving in four wheel drive on pavement can be damaging to the drive train. On pavement, the wheels cannot slip and adjust themselves, so you will "wind up" the drive train until it breaks."

I saw this comment on the landrover FAQ site and it got me thinking. I want to use the 1973 series III for winter driving when the snow is too deep for the Volvo, as well as getting back and forth to the ski hill. What is the best advice here. Shall I stick to offroad 4 wheel drive? Thanks.

Hey Runabout,
Here is my take on this. Series trucks can get pretty loose in the snow while in 2wd. I think this is because 1) there isn't much weight in the back and 2) most series trucks are running off road tires instead of snow or at least all weather tires.

I've seen front wheel drives make it through some pretty sloppy stuff when they have the right tires on but I've also run into snow covered hills that simply can't be made when it gets too sloppy and going down them can be like taking your life in your hands. In a series truck, you can run 2wd until it gets too slick and then pop it in 4wd till the roads are clear up. As long as the roads are slick enough that you can easily relieve pressure build up by slipping a little bit, you should be safe. Don't run 4wd in the rain unless boats are passing by.

Also, once you put your series truck in 4wd in the snow, it feels like a billy goat. If you've got the right tires on then you should be able to chug through just about anything on the roads. But as mentioned, don't forget about that turn up ahead or that stop light... That billy goat feeling only sticks around when you are under power. The rest of the time, you are just about as helpless as everyone else.

Cheers,
Tim
---
In case any one cares, I figured out what my problem was with the truck. I had miscounted teeth and indeed was running a slightly slower rear-end and the snapping action was from the windup. No damage as I can tell and I'm going to stick to 2wd unless I'm in really messy stuff. Thanks again for all the help!
:thumb-up:

jp-
09-05-2007, 01:07 PM
In case any one cares, I figured out what my problem was with the truck. I had miscounted teeth and indeed was running a slightly slower rear-end and the snapping action was from the windup. No damage as I can tell and I'm going to stick to 2wd unless I'm in really messy stuff. Thanks again for all the help!

In case anyone care??? I'm hurt by that.

Now Tim,

What the heck are you doing running two different ratios? Inquiring minds want to know.

Tim Smith
09-05-2007, 01:52 PM
In case anyone care??? I'm hurt by that.
He he he.


Now Tim,

What the heck are you doing running two different ratios? Inquiring minds want to know.
Would you believe a dana 44 in the rear? :rolleyes:














No, well actually its the difference between a series II and III. The front end is SIII ratio but I swapped in a SIIa rear some time ago thinking it was a SIII and after breaking the air-locking rear that the truck came with. At least I think there is a difference between SII and SIII rear's... :confused:

As an aside, it's not smart to put a washer behind the ring gear to get the clearance you need for an air-locker. The ring gear bolts will come loose at some point. I wish I had known it was put together like that before it went south on me. That locker was fun and so were the 20 something spline axles that it was using. :D

Jim-ME
09-05-2007, 03:37 PM
All Series ring and pinions should be the same ratio or atleast that is what I have been lead to believe.

luangwablondes
09-06-2007, 03:02 AM
Series landies have wind up problems when locked in 4 wheel drive. My understanding -- this is from the village idiot- but on his 5th series landy- is that the front and rear ratios are not equal. So when on 'hard pavement' you should be in 2wd. I put in Range Rover difs and it seemed to resolve the problems of the gear wind up. But on the other hand, I usually caught my 'mistake' within the 1st hundred metres, so what do I know. When you feel that thunk a couple times, you can be sure you also put alot of stresses on the gearbox.

LaneRover
09-06-2007, 11:47 AM
Even if the ratios are exactly the same, on a hard surface you get wind up when you turn because at that point the wheels in front are going a different distance than the wheels in back. Even slight turns will do this.

Brent

Tim Smith
09-06-2007, 02:20 PM
I'd like to just note that I was getting the thunk on a very very snowy day. Partially in a slide the whole way. The thing that had me concerned was that it would occur pretty regularly within a few hundred feet of the last one.

That's why I thought it was due to the slightly different ratio's from front to back. If it happened randomly or if I wasn't in a slip and slide then I would have concluded that it was just wind up from turns or road crowning.

Not sure if that makes it any clearer... :o

LaneRover
09-06-2007, 03:36 PM
Ahh yes, getting back to the actual problem!!

If you were slipping and sliding most of the time the diffs could be different ratios and you probably wouldn't have gotten the 'thunk'. As to what could cause that every hundred or so this is the only idea I have.

Any chance that there is something wrong with the front ring and pinion that takes a bit to line up, thus giving you that thunk? Something like 1 tooth from each being missing and unless they are at the samepoint under pressure the teeth on either side 'deal with it' while when they come together the pinion gear slips a notch thus creating the thunk? This would explain why it would only happen under load and only when in 4wheel drive with front hubs locked. It may seem like it was coming from the transfer case because that is what is dealing with the shock of the 'thunk'.

Try jacking up the front of your rover and spinning stuff by hand slowly to see if there is a 'click' or skip that you can feel.

I guess in theory the same thing could be happening inside the transfer case but you can easily pop the cover or drain pan and see if there are any toothless gears in there.

Brent