What could be wrong with my drivetrain?

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

Hi

Just came back from a weekend offroad trip, drice about 310 kilometers each way, plus two days of offroading.

After driving a about an hour, the transmission started acting a bit weard. about 70-90 km/h, on some hills. Shifts more or less normally, but it seemed that the lockup is a bit sharper, and also on some hills it's almost like it can't decide if to let go of the lockup at about 85 km/h, or to go out of overdrive as well.

This passed, and it worked fine all weekend driving offroad.

On the way home, it started again, usually when driving on some hills, when it shifts down or out of overdrive, I get a "clunck" in the driveline, and it got worse as I drove on. I could provoce this by letting go of the throttle and when going again, I got this "clunck" again. Almost like too much play somewhere. I made it home, and I have not been able to look more at it tonight, other than getting under right after I came home and check if something was leaking or hot.

Rear diff was about body temperature, transfer box and front diff was so hot that I could put my hand on it but not keep it there for very long, I would say maybe 60-80 degrees Celcius.

The transfer box I expected to be hot as it is directly bolted to the automatoc transmission, which should be about 80 degrees, but I wonder if the front diff should be this hot? It is tucked away close to the engine sump, but still...

Any ideas about whats troubleling my driveline? What to start looking for?

It is a 1997 3,0 td, auto as you probably guessed.

I was listening for unnormal noises but my Cooper STT's makes it difficult.

Any input or good advise wanted

Thank you very much.

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

Sounds like the backlash is excessive, you will find that the crush tubes in the diffs have taken an impact, you will have to get them looked at. Do not fear, it is not as bad as it sounds, or as urgent as you think.

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

An update:

I am aware of the radiator issues with the prados. That's why I'v been keeping an eye on it. And last year I found a small coolant leak around one of the transmission coolant lines at the radiator. I caught it in time, no internal leak, just a small coolant leak. That's why I canged the radiator. Did not flush, there was no reason for it.

About the oil cooler, it has been discussed on different forums, but most conclude that it is not recomended in our area, because of the relative cold climate we have. Summer temperatures rarely exeeds 25 degrees Celcius, and it's not unusual for 20-30 below in the winter. I have never seen the temperature gauge move even slightly above it's normal position, even when towing in hilly areas.

Did some more research yesterday. Transmision fluid is allright, it's clear and smells fine. Took it for a drive, and it shifts great, up and down as it should. The first symptoms that I experienced came after driving for about an hour, but I did not drive that far yesterday. However, the "clunk" in the driveline was there, and as apparent as it was at the end of the weekend. Letting of the throttle at cruising speed, and then go again, there is a significant "clunk", so there must be a slack somewhere, either the transfer case or one of the differentials. I have more or less ruled out the rear axle, as there is not a lot of movement possible on the propeller shaft, maybe just about 1/8 of a turn. There was also no heat after a long drive, just slightly warm to the the touch. Tried to put it in 4wd high, the clunk was there still, but possibly a little less noticeable.

The front diff has a lot more movement. I have also suspected some noise from the front end, but found it difficult to check as I have mud tires that also makes some noise.

After the test drive I jacked up the whole car, , 4H lock, both air lockers on and got my wife to drive it about 80 km/h. I found a rumble from the front diff, or more exactly, on the right side of the diff, probably the bearing inside the tube where the right drive axle is attatched. Could not say that I found any abnormal noises from the differential itself. On the other hand it's hard to get any great load on it while in the air, even if we tried braking a little. I tok great care when installing the Air Locker, but it was a pain to shim correctly. So it may be that I have screwed it up somehow, but again, I would think that it probably should have shown some symptoms earlier.

So the next step now is to remove both propeller shafts front and rear, and then try to isolate the "too much play somewhere" problem. I will have to remove the front diff anyway, and take a look inside. I also will look at the oil everywhere, and see if it's clear or if somewhere has a lot of particles in it.

Someone also mentioned that the pinion crush sleeve may have taken a hit, what could cause this to happen?

I have changed the oil in the diffs not too long ago, if I remember correctly I installed the Air Lockers at about 245000 km, changed oil again at 247500, and now I have 257000 on it.

I also stopped by the local tansmission shop yesterday, they gave me a free plastic tube of additive, they said the shift symptoms I described (not the clunk) was likely to be related to the lockup, and that was fairly common on many cars. Dirt build up in the system could cause problems with the lockup function. So they gave it to me to try, I could pay for it if it worked, if the problems did not go away it was free :-)

I also spoke to the local Toyota dealer, they had no records of others with the same problems that I have.

I am still in the middle of this, and any input is most welcome. Thank you for your time.

Cheers
Stefan

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

That would be me saying the crush tube/sleeve has taken a hit, What that means is the tube has absorbed a large amount of pressure (usually happens during off road low range driving), so now that has given you more play in the diff (backlash), you can buy another type of tube that does not crush, however the reason for the crush tube is to give you a smooth power transmission (no jerkyness) between gear changes

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

Okay, so if I disconnect the front propeller shaft, I should be able to feel the backlash, and probably also movement of the pinion flange in and out? And maybe also a little up and down?

I,ve done some heavy offroading in the weekend, but I know the front driveline is weak, so I try to be really careful.

If the crush sleeve is bad, and if I get a new one, I guess I will have to set up the diff again from start?

Thank you
Stefan

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

Okay, so if I disconnect the front propeller shaft, I should be able to feel the backlash, and probably also movement of the pinion flange in and out? And maybe also a little up and down?

I,ve done some heavy offroading in the weekend, but I know the front driveline is weak, so I try to be really careful.

If the crush sleeve is bad, and if I get a new one, I guess I will have to set up the diff again from start?

Thank you
Stefan

Yes there should be very little backlash, you will not be able to move the flange up/down/in or out, you will have to reset the diff, so you may as well put new bearings and seals in at the same time.
You may not know, but since you say you have an air locker in the front, you have doubled the number of spider gears in the diff, from standard they have 2, but if you put in an air locker, you will now have 4, so infact you have strengthened the front diff by 100%, so you will have to go easy on the CV's, do not have full compression or stretch while on full lock, as you will hurt the CV's.

[MalcomM Senior Member Find all posts View Profile Close MalcomM]

With the 343s it pays to also keep the ATF fresh and install an aftermarket oil cooler at the front of the radiator panel. It keeps those temps right down which is what you want. The front diff housing only holds 1.1L of oil so they do get hot. This is the reason why you should change out the differential oil every 20,000 kms in the front diff as the properties break down in the oil pretty fast because there is not a lot of volume in there. On those plugs on the front diff only use a 10mm hex socket, usually 1/2" drive. Don't use an allan key on them. You can buy a good one of these for about $10.00.
The Roo.

Hey John

Did my front diff aweek or so back and the hex screw is like cheese. Pretty much wound the guts out of it getting it loose. Felt like it was aluminium.
Bought a replacement from Toyo (Which I haven't yet fitted) and it does not have the hex insert anymore. Its now a normal bolt with a mushroom type hex head.

[williade Avid PP Poster! Find all posts View Profile Close williade]

however the reason for the crush tube is to give you a smooth power transmission (no jerkyness) between gear changes

Having a crush tube vs solid preload spacer will make no difference to the smoothness of the power delivery. It is used to set the preload on the pinion bearings and does not have any dampening effect. Toyota uses a collapsible spacer because its a cheaper way of setting the bearing preload.

Setting the preload with solid pinion spacers is very time consuming and would be very expensive on a mass production vehicle.

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

Where can one buy this solid spacer? Is it one type or do you have to take exact measurements to get the preload right? Any good reliable source to get the bearings and spacer from the same place?

Or should I just bite the dust and ship the diff off to some specialist store and get them to do it right the first time?

I am a ceertified car mechanic but setting up diffs it not something I have done many times. It's been over ten years since I worked in a shop.

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

Hello again,

Did some more research today. Disconnected front and rear propeller shafts. There is NOT exessive play/backlash on the front or rear diff, they are about the same. It's not possible to get any vertical or horizontal movement on either of the flanges. Combined with the fact that there seemed to be no noises from the front or rear diff (exept the bearing on the front right), I'm leaning towards the transfer case.

I will still have to remove the front diff and take a look inside. I guess any signs of exessive wear will show itself.

So next question:
What is usually wrong with the transfer case on these?
What to look for?
Easy to remove transfer from gearbox when in the car, or should I go for removing the transfer/gearbox as a unit?
Should a go for a replacement or is it specific parts inside that usually takes a beating and can be replaced?

Sorry for all the questions, I'm just trying to make the best of it.

Cheers

Stefan

[williade Avid PP Poster! Find all posts View Profile Close williade]

On the way home, it started again, usually when driving on some hills, when it shifts down or out of overdrive, I get a "clunck" in the driveline, and it got worse as I drove on. I could provoce this by letting go of the throttle and when going again, I got this "clunck" again. Almost like too much play somewhere. I made it home, and I have not been able to look more at it tonight, other than getting under right after I came home and check if something was leaking or hot.

I'm kind of surprised no one has suggested this yet, but it could be that the slip joint on one of the prop shafts (more likely the rear) is either running dry or has too much grease.

If the slip joint is looking a bit dry and crusty give it a few squirts with a grease gun. If its oozing grease, remove the grease nipple and unbolt the uni joint flange and drain some of the excess grease by pushing the drive flange back into the slip joint.

It the slip joints are ok one way to find the source of drive line backlash/play by putting the transfer case in low range, standing on the brake pedal and shifting the transmission between reverse and drive and listening for any clunking.

Failing both of the above, check for perished suspension bushings.

[MalcomM Senior Member Find all posts View Profile Close MalcomM]

If the slip joint is looking a bit dry and crusty give it a few squirts with a grease gun. If its oozing grease, remove the grease nipple and unbolt the uni joint flange and drain some of the excess grease by pushing the drive flange back into the slip joint.

OK you got me, why would excess grease cause clunking?

[williade Avid PP Poster! Find all posts View Profile Close williade]

OK you got me, why would excess grease cause clunking?

Because it would prevent the joint from doing its job.

How is joint supposed to travel inwards if the whole assembly is completely filled with greased? It would be like hydro locking you engine.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Where can one buy this solid spacer? Is it one type or do you have to take exact measurements to get the preload right? Any good reliable source to get the bearings and spacer from the same place?

Or should I just bite the dust and ship the diff off to some specialist store and get them to do it right the first time?

I am a ceertified car mechanic but setting up diffs it not something I have done many times. It's been over ten years since I worked in a shop.

My diffs have solid spacers. I ordered them from Just Differentials in USA (along with the ratios and rebuild kits).

They come with shims, which are used to get the preload correct. I think it's more work to install than the crush sleave, but a stronger result.

PS: Diff work is a specialist field, most mechanics send them to specialists.

EDIT: BTW, my first thought when reading your original post was bearings.

[Stefan E. Lurker Find all posts View Profile Close Stefan E.]

I'm pretty sure that both drive shafts are ok, I'm aware of the usual overfillig problem. I greased the U joints before my weekend trip, but did not grease the slip yokes. I grease at every oil change.

I also changed one of the output seals on the transfer case, and then I removed the nipple to get enough compression on the driveshaft to be able to get it over the studs.

The clunk in the driveline I'm getting more and more sure is transfer box related. I suppose I will have to remove it, and see whats going on.

Any good source for internal transfer case parts?

Thanks

Stefan