1995 Rav4 Possible Diff Clunk?

[rav4kay]

Hi, I have just got myself a nice little 1995 Rav4 3door auto, it has a clunking noise when driving, it sounds like the diff is locked on. Is there anyway to switch it off? Thanks

[crofter]

Hello Kaylea and welcome to this great club

Don't think there is a switchable diff lock on your auto so suggest that the the propshafts are checked for wear on the universal joints to start with.

"When driving" does not give too many clues to the problem.

Does it make the noise all the time or say when you are moving the throttle or going round a bend?Is the noise at the front or back?

Do you see what I mean?

The more info you give means there is a chance that someone may be able to give you a more definate answer and you will find there are knowledgable members on here who will help

Del

[rav4kay]

Thanks for the reply.

When I put it on full lock and drive foward or reverse its a constant clunking (cant tell if front or rear) which sounds like the diff lock engaging. When im driving on the road the clunking is coming from the rear.

Is there any chance the diff lock can cease or get stuck on?

[gjnorthall]

The 4.1 auto is fixed 4WD but has a sort of self controlled, on-demand diff lock - it's not the same as the manual car which has a driver operated switch to lock the differential. The early auto diff system can be troublesome particularly if the car has had a hard life. Signs of a faulty diff system (i.e. not disengaging when it should) is that the car drives fine in a straight line, but on a lock, there's a peculiar sensation - essentially one wheel is trying to turn faster than it needs to - this gives a clunking / skipping sort of sensation. It's easy to confirm by jacking up the car and checking that the diff is locked across the axle. A locked diff on non-slippy normal roads can cause damage and can be hazardous.

[three5]

Hi, I have just got myself a nice little 1995 Rav4 3door auto, it has a clunking noise when driving, it sounds like the diff is locked on. Is there anyway to switch it off? Thanks

Hi Kaylea,

There is a know problem with the diff mounting bushes on this model. These rubber bushes wear and allow the diff to move about when you put you foot on the throttle or remove it. When you drive it check to see if the clunks occur when you change from acceleration to engine braking. It's a lot cheaper to fix than a new diff!

[rav4kay]

When im driving on the road (which im not going to do til I find out what it is) its a constant clunk from the rear. If I go super slow like on my drive way and turn it on full lock, its a constant clunk from the front?

[rav4kay]

Also, when I was on the bypass(only going about 50) it was constantly clunking but when I take my foot off the accelerator it stops, until I press it again. And it also does it when the auto box is changing gear but not all the time.

Hope that makes sense.

[Big Kev]

Chris/Gareth.......humour me here.......is there any way this clunking could be that ol' chestnut of the discs' wear ridges lifting and dropping the brake pads noo and then.....?

Apologies Kaylea.......no mean to talk over you there.......welcome to this forum. Is it a pronounced "clunk" or does it end in a wee metallic ringing......?

[three5]

Chris/Gareth.......humour me here.......is there any way this clunking could be that ol' chestnut of the discs' wear ridges lifting and dropping the brake pads noo and then.....?

Apologies Kaylea.......no mean to talk over you there.......welcome to this forum. Is it a pronounced "clunk" or does it end in a wee metallic ringing......?

Hi BK,

the "clunk" rather than a a more metallic sound pointed me in the direction of the diff mounts. It could very easily be rear disks if the noise is constant. Where is Bothy when we need him?

[Big Kev]

Chris/Gareth.......humour me here.......is there any way this clunking could be that ol' chestnut of the discs' wear ridges lifting and dropping the brake pads noo and then.....?

Apologies Kaylea.......no mean to talk over you there.......welcome to this forum. Is it a pronounced "clunk" or does it end in a wee metallic ringing......?

Hi BK,

the "clunk" rather than a a more metallic sound pointed me in the direction of the diff mounts. It could very easily be rear disks if the noise is constant. Where is Bothy when we need him?

He may be in hospital having another mouth installed to help with his drink problem........he only has one at the moment.....

[gjnorthall]

There's not enough information about the clunk - for example - is it rhythmic i.e. increases in frequency with road speed, is it a knock or click?. From the description that the clunk is continuous when driving, appears to come from the back and front etc - it would tend to rule out a brake pad issue. There's only a limited amount of analysis that can be made from a description, and whilst a couple of possibilities have been put forward - these now need to be checked out.

It's easy to be critical, but why would someone buy a car with an obvious fault without fully checking it out? In my time, I've seen dozens upon dozens of newly bought cars with difficult / expensive problems generally resulting from sellers taking the disposal route when they're unable / unwilling to fix problems. Faults are a good price negotiating tool as long as you're confident about the nature of the fault.

[rav4kay]

Hi, just had it jacked up in the air all 4 wheels off the ground, put it into drive all 4 wheel start to move then the rear passenger and front drivers stop turning. Does the same in reverse also. Any ideas?

I think that the diff lock has ceased on but I want to know if there is any way to disengage it completely for now?

[gjnorthall]

The car is behaving as it should - the front and rear diffs are each rotating the primary wheel. Had you attempted to slow down the rotating wheel (with a block of wood against the tyre tread - not by applying the brakes) - the opposite wheel on the axle would have started to turn indicating correct diff action. Your test wouldn't suggest that the rear diff lock is engaged - though the situation might change when driving the car. Did the 4 wheels rotate by hand smoothly and without excessive backlash? Did you get an opportunity to check the diff mountings?

[rav4kay]

Hi, I have just been told it is the transfer box and rear lower control arm.

[gjnorthall]

The track control arm is no big deal - it must be quite well worn to cause a clunk. The transfer box is a bit of a surprise - they're usually bullet proof despite the fact that they tend to be forgotten - I've seen high mileage 4.1's that have never has a transfer box oil change -some 4.1 transfer boxes whine quite a bit but they tend not to get any worse. It would be interesting to know the nature of the problem. Under normal circumstances, I'd recommend getting a reliable part like this from a breakers - but I think you'll struggle finding an auto gearbox version. However I suspect that your issue isn't mechanical - theres not enough info at present to be definitive. I don't have much experience with the 4.1 auto transmission but I know the trials and tribulations of the complex diff-lock system on the manual. Problems often result from vacuum leaks but the usual issue is for the diff-lock to stick so it either doesn't engage or won't disengage. Your previous descriptions did suggest that the diff-lock was failing to dissengage.

[rav4kay]

The clunk from the rear arm is like drive over the cats eyes in the road, that sort of noise. Best way I can describe it.

What oil do I need in the transfer box? And where is the filler for it?

[rav4kay]

The transfer box/ diff is working. It just seems to engage and dissengage randomly as im driving.

The longer its driven on the road (about half an hour) the clunking from the box gets less.

[bigend]

Someone hasn't put the wrong grade of oil in have they?.

Keith

[rav4kay]

Someone hasn't put the wrong grade of oil in have they?.

Keith

I've no idea. :/ Only got the car last week from an auction.

[gjnorthall]

The track control arm shouldn't be too much of an issue - it's a straightforward job. The random operation of the transfer box / diff is unlikely to be related to the mechanical condition or lubricant - however it's worth changing the oil. The drain is on the base of the unit and the filler about 2/3rds of the way up. Oil is 75W90 GL5 gear oil. The diff lock is operated by a diaphragm in a vacuum chamber - the vacuum is provided by the inlet manifold. On the manual - applying the vacuum applies the diff lock and I presume the same is true on the auto. To check you're on the right lines - it might be worth isolating the vacuum supply. If the car is then OK - at least you can then use it and it will be in 4WD mode. Getting to the root of the problem is then a more difficult issue for another day.

[rav4kay]

How do I isolate it? Sorry if im sounding thick, I've no idea what im talking about so im repeating all of this to my fella.

[gjnorthall]

Bit of investigative work I'm afraid. The easiest way would be to find the vacuum connection on the inlet manifold - remove it and blank the takeoff. There's a few connections to the manifold - brake servo etc so it's a case of tracing back each connection. On the manual, the vacuum pie is connected via a couple of solenoid valves on the bulkhead and this is probably the case on the auto. The vacuum chamber itself is fairly obvious - it's quite a large chamber bolted on to the transfer box - the box itself is cast alloy whilst the vacuum chamber is a carbon steel fabricated pot.

[rav4kay]

Thank you.

I dont suppose there is a diagram of the transfer box anywhere is there?

[gjnorthall]

You can access data on the link below on a pay per hour basis.

http://www.toyota-tech.eu

[bothwell_buyer]

I doubt its the transfer box. I thrash my transmission on both my RAVs and bever any probs with transfer box.

2 things

one is the rear diff mount which is probably soft and can be stffened with silicon gunge.

the other is the central prop shaft mounting bearing which can cause knocks if worn.

Lastly get the bushes on the rear suspension checked. the cheapest way is to put the car through an MOT !!!