biffidun

Well it is all back together. I had to reinstall the pinion shaft several times to get the lash setup. You can see in the photo how there are shims on the pinion carrier that set the gap. The new shaft ended up with fewer shims, so the machining is not identical.

Another tip for those who might tackle this, is to use the steel disc plate that bolts up to the ring gear axle (see picture). Pick up some 2.5" bolts (the stock bolts are 1.5" in length) and then use the longer bolts and the disc to pull the axle through. Once you are close enough swap the stock bolts in and tighten it up.

The job is not that bad. The big headache for me was pumping the gear oil into axle since I don't have a great pump. I just have some $10 hand transfer pump.

Anyone want to buy my 4.5 gears??

Well I had to break the bearing to get it off. The part number was on the covered side (or course). New bearing arrives tomorrow. Just in case someone is interested the main inner bearing on the spindle of the pinion is a Timken 5760.

The freezer trick won't work since the whole thing cools at once. I had to use a bearing separator, which due to the design of the spindle impacts on the bearing cage. The force to spread it deforms the cage.

A new bearing on Amazon is $65, I got one for next day delivery from a local supplier for $95. Not bad really.

Thanks for the info. I have the ring gear pressed on, but the bearing on the pinion shaft is being a B****. I don't have a bearing separator large enough, so I might have to pay someone to get it off or just buy a new bearing from Mack.

Parts look good.

Assuming you have a CRD92 front and CRD93 rear;

Front axle: (fine) 24KH11073 (PAI7534) Coarse 24KH1917 (PAI 7530)

Rear axle: (fine) 24KH1956 (PAI7541) Coarse 24KH1915 (PAI7540)

Sometimes you add a "0" to the end of the PAI#

There might be an "A" or a "B" beside your Mack part# - don't sweat it, the newer versions of parts have a "B" ending indicating a minor improvement.

When I took mine apart the yoke was loose and there was endplay in the stub axle bearing. It must have been like that for some time. What was amazing was that the gears look perfect! no wear whatsoever. I think all the stress about setting the gears up right is a bit overplayed. I've got some paste I put on the teeth to make sure they are swiping properly, but I'm not too worried. I'll start with the shims that were in there to begin with.

Make sure you run Hypoid gear oil in youre axles - anything else will ensure rapid wear!

Out with the old and in with the new. I have to press the "ring" gear off the stub axle. The PAI part number was 75400.

The 4.5 gears look great - just not the right ratio. Anyone want to buy them? It would help offset the $400 for the 4.17 gears

I'm not sweating the setup. Just the part numbers. I'll do a better job than the knuckle draggers that have worked on my truck in the past at the stealership.

That much I have figured out, thanks. I am pretty sure I have the right part number from Mack for a 4.17 gear set - just looking for some confirmation.

OK, so I have the gears out and now I have to figure out what to order. The gears that came out have 47KH3397 stamped on them, which (given my luck) does not match up with anything at the local Mack Dealership.

From what I can tell this is a late 70's to early 80's axle.

It's the rear axle, so I am going to assume the axle is a CRD93.

I am trying to swap the gears to make the axle a 4.17 to match the fron axle.

Could someone help me figure out what gear set I need to get a 4.17?

I looked up a PAI/Excel part number of 7540, which corresponds with a Mack PN 27KH1915

So what is the deal with the part number that came out of the axle (47KH3397)?

Thanks. I'll tackle it ASAP. If I think of it I will post some pictures. There is next to nothing on the net about this stuff.

a used rear carrier is about $1500 ... the 45's (ring and pinion gears) are about $300

Not worth calling a lawyer and no they won't own up to it. The truck drives like a bucking bronco.

I'll just chalk this one up to a lesson learned.

Ok, so I have finally narrowed down my power divider issues to mismatched drive axles. Front drive axle is 4.17 and rear is 4.5

I have counted the bull gears in both diffs and they are both 55 teeth. I have opened the rear diff at both sides and removed the plates with 3 bolts that appear to center the top shaft.

My plan is to switch the rear drive to 4.17 It appears as though I have CDR92, CDR93, CDRPC92 or CDRPC93 - all information on the axle has rusted off so I'm guessing two things, 1st is that it doesn't really matter, 2nd is that I have a CDR93 rear... I figure once I have the gears in my hands I will know what to order (fine vs coarse etc...)

How do I get the gears out? Do I rotate a wheel and tap the top shaft towards the passenger side to slip the transverse gear off the key?

Do I pull the yoke?

I'm worried that if I tap the top shaft too far over I will drop something into the bowl.

Any tips would be nice.

Well I've gone and had a look at the truck. The cab doors are a mess (need new locking mechanisms, windows fall down). The center rod (?) that holds the rear suspension beams to the chassis is snapped. Both axles are leaking. Power steering gear box is leaking badly. All of the above is repairable. The big problem was the 8LL. I could hardly drive the thing. I thought it was me so I had the other guy drive it and he had to pull over to get it into gear a couple of times. I think the shift forks are shot. I have no idea what it would cost to repair the trany. I've used 8LLs before and they were WAY tighter than this thing. It all makes me wonder just how many miles are really on the thing.

I think I'm going to pass.

I might even keep my old beast. "Better the devil you know, than the devil you don't"

Thanks for the advice guys. I hope to inspect a couple of trucks in the next week. I'll let you know how it goes.

What would be an acceptable amount of engine hours (assuming they can tell me what they are) ?

Yup, I'm in Ontario. I think we are talking about the same truck. There have been a few of those ex-Rexdale trucks around. I think I will go have a look.

I've been told my old DM685 needs too much to safety this year, so I'm in the market for a replacement. I'm looking at a 1998 RB688S, but it has 388K miles on it. I use the truck to haul woodchips twice a week to our farm - so low mileage once I have it.

The question is, do these trucks need overhauls every 300K miles (like Internationals) ?

What should I look for when I go check out the truck? I usually just look for leaks, rust and how it feels when I drive it.

Specs are

400HP (not sure which engine)

8LL

22K front

44K rear

Hendricks Rubber block suspension.

Thanks for any and all help.

Well I think the plate that indicated the gear ratios is gone or not legible on either axle.

gallery image:http://www.bigmacktrucks.com/index.php?/gallery/image/14066-rear-axle-with-peanut-power-divider/

I guess I just have to jack up one side of the rear and turn the drive shaft and count revolutions of the wheels. I'm just concerned that it will be difficult to see the difference between a 3.86 and a 3.87

On another note, I can get a 3.87 top gear set is this all I need to change the ratio or do I need to remove the whole diff?

Thanks for any help I get.

Well I replaced the peanuts less than 1000 miles ago. I think it is time to jack up both rear axles and see if the ratios match. I have had problems since I bought this truck over a year ago. I don't put a lot of miles on, but once there is any kind of sustained load it starts banging up the driveline. The problem went away when I replaced the peanuts (they were worn), but it has resurfaced. I didn't replace the inner cam,.... maybe that was a bad idea.

All tires are new.

No thoughts? Guess I'll just do it.

Hi there. I would like to know if I can pull the drive shaft between the rear axles and make my truck a single axle drive? I am having some power divider issues and would like to drive the truck till I get the thing sorted out. I never was able to wrap my head around the peanut and wedge power divider, but I am thinking it might just send all the drive to the flange where the rear axle used to be... meaning the truck will not move.

Can this be done? Is there a way? I don't encounter any muck as I am driving on roads 100% of the time so traction is not an issue.

OK I got clarification on the repair and the price includes quite a bit more little stuff so I am having them go ahead and do the work. Sorry for temporarily hijacking this thread...

Hi guys,

1976 DM685S, Mack rear end (travelling axle type)

I had my truck in for my annual safety and they say all I need is a new torque rod, torque rod assembly and seal. I have snugged up the assembly a couple of times over the last year, so it is possible that the mount holes are out of round.

They want $744 for parts and $1200 for labor!! I have some mechanical ability so I was thinking I could tackle the job myself. Does $1200 seem extreme on the labor end of things? My rear is a travelling axle type (not camel back), so it just has rubber "hockey pucks" so how hard would it be to keep things aligned while the bushing is out??

Any comments would be nice as I have to decide if I give them the go-ahead or not...

-Derek

Thanks Rob. I checked the magnets on the tranny and other than a fine metal sludge nothing big. The drive axle may just be it. I've never touched wedges before, is this a scary thing or not too bad? I know they should be replaced as a set, but is there anything I should know? I do not have air lockers in the back fwiw.