Tearing down my HJ47 troopy

[gswest]

I was thinking I could remove the front driveshaft and spin the front tires and count the rotations of the pinion in relation to the wheel rotation. If one side was jacked up, would that give an accurate reading. I obviously don't have a good understanging of the differential.

 

[lostmarbles]

I was thinking I could remove the front driveshaft and spin the front tires and count the rotations of the pinion in relation to the wheel rotation. If one side was jacked up, would that give an accurate reading. I obviously don't have a good understanging of the differential.

What do you gain from removing the driveshaft? (In 2WD that driveshaft spins freely in the transfer case anyway.)

And I'm not sure who has the better understanding, you are me. (Maybe neither of us has a good understanding )

Tell you what ... I'll go and jack just one front wheel of my BJ40 after I've had breakfast and rotate it a few times (counting the no. of times) and I'll observe the matching number of rotations of the front driveshaft for you and report back in an hour nor so. (My free-wheeling hubs are always left in the locked position - except when I go on long road trips so I don't need to alter them.)

This practical experiment will sort it out!!!!!

 

[lostmarbles]

OK. Just done it..

I put a piece of masking tape on the wheel (that I could line up with a joint in my concrete driveway to accurately count wheel rotations) and a couple more pieces on the drive pinion.

Here's the result:

I started rotating the wheel and noticed that for every rotation of the wheel I got very slightly more than two rotations of the driveshaft. So I then kept rotating it (and counted the revolutions) until that sum of those little extra bits amounted to another complete rotation of the driveshaft. That took 18 wheel rotations (because 37 = 36+1).

So there you go Scott.

If you have 3.70 diffs, I'll leave you to find their equivalent of my "18-to-37 ratio".

 

[gswest]

My god! Thanks Tom! Your obviously right, I have a problem conceptualizing how the diifs work. But clearly when its in 2 wheel drive the front driveshaft is free. I'd like to think that would have occurred to me I was was removing it and it kept spinning in my hand, but maybe not. I'm on duty today, so tomorrow I'll do the procedure you did and report my finding here. You saved me some serious effort, I'm in your debt.

 

[gswest]

My ratio should be 18 tire revolutions to 33.3 pinion revolutions if my math is correct. I'll find out here in a bit.

 

[gswest]

I did the experiment and I got the correct revolutions to equal a 3.70 diff ratio. 18 to 33.3. So, at least I know the diff is the correct ratio. I thought I checked that before the install, but there was a slight amount of doubt. Now I have to determine why there was so much vibration in 4 wheel drive. The first thing i noticed was the transfer case shifter was making noise. I did try it in low and high and I think low range was worse. I looked at the front drive shaft to make sure it was tight and on correctly. The Warn locking hubs shouldn't be an issue, right? They appear to only go on one way. I'm going to try it again in 4 wheel drive for a very short distance on the road, if it still sounds bad, I may put it on jack stands and observe the operation from below the truck. There could be something wrong with the transfer case, but it certainly works perfectly in 2 wheel mode.
Thanks again for the help Tom.

 

[lostmarbles]

My ratio should be 18 tire revolutions to 33.3 pinion revolutions if my math is correct. I'll find out here in a bit.

I did the experiment and I got the correct revolutions to equal a 3.70 diff ratio. 18 to 33.3. So, at least I know the diff is the correct ratio. ..

You are correct. 18 to 33.3 does indeed match the diff ratio of 3.70 alright. But to deal in full revolutions (which is easier) that amounts to 20 turns of the wheel matching 37 turns of the driveshaft.

And all this stands to reason when you look at the number of teeth on the pinion (where the driveshaft enters the diff) and the number of teeth on the crownwheel (connected to the axle shafts)

For the 4.11 diff ratio we have a 9-tooth pinion driving a 37-tooth crownwheel meaning that when the vehicle is moving, 37 driveshaft-rotations will give 9 wheel rotations. But since in our testing we are turning only one wheel and working through the spider-gears we need double that number of wheel rotations (18) to match the 37 driveshaft rotations.

Similarly for the 3.70 diff ratio we have a 10-tooth pinion driving a 37-tooth crownwheel meaning that when the vehicle is moving, 37 driveshaft-rotations will give 10 wheel rotations. But since in our testing we are turning only one wheel and working through the spider-gears we need double that number of wheel rotations (20) to match the 37 driveshaft rotations.

.......Now I have to determine why there was so much vibration in 4 wheel drive. ....

Are your slipjoints both at the transfercase end of your driveshafts and do you have the alignment of your driveshaft yokes correct Scott?

This stringline shows my yokes in the correct alignment:

Misaligned yokes (by assembling the slipjoint with the yokes not orientated correctly) will certainly produce vibrations because the driveshaft will be trying to both accelerate and decelerate your vehicle during every shaft rotation.

 

[gswest]

Thanks Tom,
My front slip joint is facing the differential. Not only that, but I had to switch the mounting flange on the front shaft to mate up to the newer differential and I put it on the wrong end. So, I get to replace both u joints now in order to switch the flanges and correct my screw up. But, at the end of the day, that's easier than removing the transfer case or differential to repair those parts. Thanks for the help,,again.

 

[lostmarbles]

Thanks Tom,
My front slip joint is facing the differential. Not only that, but I had to switch the mounting flange on the front shaft to mate up to the newer differential and I put it on the wrong end. So, I get to replace both u joints now in order to switch the flanges and correct my screw up. But, at the end of the day, that's easier than removing the transfer case or differential to repair those parts. Thanks for the help,,again.

Hmmm.

While I think the correct layout for your HJ47 slip-joints should be the same as mine, that is, with both of them at the transfer case ends of your propeller shafts ... I don't think it is a major "faux pas" to have the front one reversed. After all, in 1985 Toyota even had it this way (as far as I can tell from looking at a 1985 60-series owners manual).

Having the slip joint at the opposite end (from it's original ex-factory position) certainly shouldn't produce vibration.
So I'm not sure it's worthwhile correcting it...

In other words, I think it might be better to leave it be considering how much work is involved in correcting it and that you won't gain anything in doing so (other than gaining a more "ex-factory drive layout" and perhaps keeping that slipjoint higher and thus further away from water-immersion during water crossings).

More importantly - Are your yokes in line (as per my last photo) ... because having those out of alignment will certainly produce vibration (particularly if your driveshaft angle is significant).

 

[gswest]

Tom, I'll bet they are not in alignment. Tomorrow I'll check that and post up my finding. My girlfriend assigned me on a project to fix her bathroom tile and vanity. So, my efforts are diverted temporarily. I'll be back on the important stuff soon!

 

[gswest]

I took the front drive shaft off and in the process I noticed a substantial amount of play in the double Cardan type U joint. And it wasn't aligned correctly as well. So I ordered the U joints and a centering ball repair kit?? We'll see if that and the alignment fix solve the vibration problem. I saw a member here had a similar vibration and noted the same play in his Cardan joint. I'm assuming it should be fairly tight like any u joint, but with 2 u joints together there may be some play as part of it's function.

 

[lostmarbles]

I took the front drive shaft off and in the process I noticed a substantial amount of play in the double Cardan type U joint. And it wasn't aligned correctly as well. So I ordered the U joints and a centering ball repair kit?? We'll see if that and the alignment fix solve the vibration problem. I saw a member here had a similar vibration and noted the same play in his Cardan joint. I'm assuming it should be fairly tight like any u joint, but with 2 u joints together there may be some play as part of it's function.View attachment 1103733

I'm not familiar with these "double cardan joints" but being just two universal joints coupled together, just check each UJ of the pair INDIVIDUALLY for abnormal wear/movement where the needle-rollers sit.

As a unit, it'll definitely feel more "sloppy" than if there were only one UJ there so don't be fooled by that.

 

[Weber Sarge]

Be wary of the center ball - if the shaft tip is worn a new kit won't fix it , have to take it to a driveline shop for the repair .

Almost all Japanese brake adjusters tighten when moving the star wheel towards the axle , btw .

Sarge

 

[gswest]

Sarge,
You sound like you have some experience with these Cardan joints. With mine on the truck, you could move it around very easily. Should they have a lot of play when they're installed?

 

[Weber Sarge]

No, never . It's common the center ball is worn out , even more common the rebuild kit won't work due to the wear on the center shaft tip .
Sarge

 

[gswest]

That's good to know. Hopefully the thing is repairable. I have a shop that's familiar with these joints, so when the parts show up I'll find out if I need a new shaft altogether. I've read here that some guys try to eliminate the Cardan joint. I wonder if that's a cheaper alternative to replacing it with the original equipment, if I need to.

 

[lostmarbles]

Obviously there's more to these "double cardan joints" than what I thought...

And I didn't even know before that any 40-series models were sold with them fitted!

But looking at the EPC, it appears that from august 1980 they appeared on HJ47 models and from Oct 1981 on all other 40-series too (at least in the GENERAL market).

And what's more, I see that at the same time as the double-cardan was introduced, they turned around the front driveshaft to place the slipjoint at the diff end - so you had that correct all along.

So ... sorry Scott... I'm obviously out of my depth on the subject of your front driveshaft. (I was thinking about this at work last night and realised I might be.)

Cheers - Tom

 

[gswest]

Not to worry Tom,
You have only what you have experienced there to use as a reference. You acknowledged "no knowledge" of the double (Cardan) u-joint. I'm happy with every bit of your input. You have saved me countless hours of searching for answers. This so-called Cardan joint is my problem; you don't have it on your truck. You'll probably never see one!
But, either way, Thanks for all of you're input!

 

[gswest]

I dropped the front drive shaft off at a drive line shop close by. They confirmed that if the stud that the centering ball connects to is bad, there is no repair they can do for the drive shaft. A new drive shaft will be needed, or a used one. If that is the weak point, as I've read here, I'm giving myself a 50/50 chance of getting lucky. My fingers are crossed!

 

[lostmarbles]

I dropped the front drive shaft off at a drive line shop close by. They confirmed that if the stud that the centering ball connects to is bad, there is no repair they can do for the drive shaft. A new drive shaft will be needed, or a used one. If that is the weak point, as I've read here, I'm giving myself a 50/50 chance of getting lucky. My fingers are crossed!

I wonder why Toyota suddenly decided they needed to use a double-cardan in those final 3-4 years of 40-series production.

I borrowed this image from a Jeep board and I'm guessing the Toyota one is of similar design:

Do you have an idea why?

I'm wondering if you can revert to the old-style (without the double-cardan) but then Toyota isn't stupid. I reckon something must have changed in the driveline to make the double-cardan necessary when it wasn't necessary before.



Edit: I see with the double-cardan the front axle gets tilted to point it's drive pinion up towards the transfer case output (unlike mine where my transfer output and my diff pinion are parallel to each other instead):

If this is true then your front diff is presently angled quite differently to mine.

PS. I'm guessing the double-cardan is required when the distance between the driving and driven flanges is shorter than normal (and where there is still significant "altitude drop" in the driveline).