Rear Diff. 1970, Noisy, question (1 Viewer)

[Scota4570]

I have too much noise and vibration on the highway. It has for years. It is not a grinding type of thing but a harmonic and out of balance type of thing.

My rear diff has about 10* of radial slop on the drive line. The U-Joints are tight.

I noticed vertical and horizontal play on the rear diff flange that appears to be coming from the shaft to bearing fit.

To me that indicates the bearings and or shaft could be spun or obliterated, which does not seem to to be the case.

OR, or the bearings were never set up right. Maybe the bearings seated themselves after being rebuilt years ago?

They are tapered seat pin bearings, like a trailer wheel bearing, so the position of the castle nut (#33) matters? As a temporary measure can I tighten the castle nut in the diff flange to take slop out of the shaft?

I understand that the diff needs to be rebuilt. Unfortunately I can not do it and nobody in my area can be trusted to do it right.

 

[B y r o n]

Sounds like it is time for another rebuild. I say this because if you are thinking about just replacing the pinion bearing you have to tear it apart. If it is torn apart you might as well go though the whole thing and correct any issues.

 

[65swb45]

The whine will be there forever. That said, it is often possible to adjust the preload to a useable point. But the preload will be nowhere near the factory specs. In fact, it’s likely that trying to tighten it to anywhere near factory specs will lock it up completely.

 

[Scota4570]

So, if I tighten the castle nut while testing the rotation for binding or roughness, I may be able to reduce the slop and improve the noise an vibration?

It seem to me worth a try. I have nothing to loose.

 

[sogncab]

Pinion bearings likely close to done.

Tightening anything will be short lived and has potential to take out the gears.

 

[mattressking]

So, if I tighten the castle nut while testing the rotation for binding or roughness, I may be able to reduce the slop and improve the noise an vibration?

It seem to me worth a try. I have nothing to loose.

Yes, but you need to lift the truck and take the wheels/axles out to check for binding. That said, I'd recommend removing the pinion seal and inspecting the bearing to start before just going to town with a wrench, you're liable to put yourself in a worse position by tightening blindly to remove play.

Even if you tighten, the life span is already over, so it is time for a spare 3rd to get swapped in. Find a spare front 3rd from a 40 and swap it in, easiest/cheapest path forward.

 

[Scota4570]

You lost me. "Spare 3rd".

I called a major vendor of rebuild parts sets for 1970 rear diffs. I was fully prepared to buy all the parts needed on the spot.

He suggested checking the castle nut to see if it was loose with out my asking. He suggested tightening it. So, I put all four corners up on jack sands. I took the drive shaft off. I made note that the diff flange was lose and was the castle nut. I took the flange off. IT seemed to be in good shape. I then put it back and snugged it it. The play disappeared. The flange tuned easily and smoothly by hand. Not binding or badness. I put in a new cotter pin and put the drive line back. I spun up the tires on the stands, seemed fine.

I drove and it and it now drives nice, like it used to. After about 10 miles at highway speed I checked the diff for being hot. IT was no hotter at the flange bearing than anywhere else, just comfortably warm.

Don't know if I did anything worth while. My father had a lot of shade tree guys work on it. IT is very possible that the castle nut has been loose for years. It is also possible the diff was worked on and not assembled properly.

Any Idea how to determine what gears I need to order? The shop that I checked with to rebuild it said that there are several gear sets with the factory ratio. That seemed confusing because SOR sells one type.

Thanks,
Scot

 

[sogncab]

I'd look too see what condition the gears are in before ordering a set.

Might be fine and you had a growly bearing

 

[jim land]

Your ratio is 4:11
You can swap the 3rd front to rear , the front is probably in better shape

 

[Scota4570]

Thanks for the interest and comment.

Firstly I am not primarily a mechanic, more a machinist. I play with old cars and maintain them. It is not my main hobby though. So, I have a lot of knowledge gaps. I do enjoy learning new things and working on stuff so here I am.

I have never taken a diff apart. What is a "3rd"? The pinion?

Question, what determines the end play of the the Pinion? Shims and the bearings? With the castle nut tightened I have rotational play between the pinion and ring gear when I turn the flange and before the wheels turn. The pinion is not binding. The bearings run smooth with no hint of roughness. The issue vibration issue was caused by slop between the flange and pinion splines.

That slop may have worn those splines. Driving at highway speeds that induced the vibration is probably less than 50 miles over the years. It was primarily a ranch truck. The splines slide together easily. I have no reference on how easily they should go together. IF the castle nut is loose is wiggle expected?? Does the castle nut draw up the flange on a tapered seat?? By drawing it up tight I eliminated the vibration.

Since the root cause of the vibration was slop between the pinion and flange splines caused by a lose castle nut, I might have a solution. Loctite shaft sealant will lock those two parts together. The joint can be released with heat when rebuild time comes.

The worst outcome is trashing diff parts that I intend to replace anyway.........

 

[charliemeyer007]

There are some really good vids for setting up diff's. Not sure there are any old LC ones.
Putting them in/out many times adjusting stuff with shims is "normal". Pay attention to the arrangement when you first take it apart.

 

[franklin40]

“third” is short for third member or a drop out differential.

you could find a used (spare) one from a part out truck. just search here on mud for year and gear ratio as the drive shaft flange needs to match your drive shaft and the gear ratios of your front diff. they’re relativity easy to swap out with basic tools. there is not set up to do it’s really just dismantle and install. @cruiseroutfit builds diffs too and do a nice job. you could send yours in as a core and they’ll rebuild it. shipping something that size might suck though. either way it sounds like you need a new/different diff with good bearings.

have you checked the gear oil for metal flakes? that’ll also give you a clue if there are bearings or gears that are wearing.

 

[sogncab]

Being a machinist, setting up a diff should be a non issue.

The third member is what is hanging off the front of your rear axle housing. It houses the differential assembly.

Basically the pinion depth is set by shims. You should be able to measure the stack of shims that come out, match that and either be extremely close, or spot on

The the carrier is adjust left or right by threads in the housing.

To be fair, I've never set one up entirely on my own. I'm good friends with a driveline mechanic, so he's always been present for brains.

There is a handful of videos setting up LC differentials, but they're all basically the same.

 

[pb4ugo]

In the diagram in your 1st post item 24 is the 3rd member, it contains all the bearings shims and ring and pinion in your diagram. It has to be removed to rebuild it, or you can find another good used 3rd and swap it. A frt 3rd can be interchanged with the rear. The frt and rear gear ratios must be the same. A frt 3rd usually has less miles on it than the rear. The slop you described most likely wasn't between the flange and splines. It was slop between the ring gear and pinion gear. The mesh between the 2 are critical and require several measurements for proper set up. 1st is pinion depth which places the pinion and ring gear engagement. Once proper pinion depth is achieved the the pinion needs proper preload to seat the bearings. 2nd is backlash which is the gap between the ring gear and pinion. To determine backlash you adjust with side gear nuts and use a dial indicator on the ring gear and hold the pinion still. The carrier is the part the ring gear is bolted to. Inside the carrier are spider and side gears. Most likely the rotational slop you are experiencing is the spider gears loading and unloading against the inside of the carrier which is normal.

 

[cruiseroutfit]

Thanks for the interest and comment.

Firstly I am not primarily a mechanic, more a machinist. I play with old cars and maintain them. It is not my main hobby though. So, I have a lot of knowledge gaps. I do enjoy learning new things and working on stuff so here I am.

I have never taken a diff apart. What is a "3rd"? The pinion?

Question, what determines the end play of the the Pinion? Shims and the bearings? With the castle nut tightened I have rotational play between the pinion and ring gear when I turn the flange and before the wheels turn. The pinion is not binding. The bearings run smooth with no hint of roughness. The issue vibration issue was caused by slop between the flange and pinion splines.

That slop may have worn those splines. Driving at highway speeds that induced the vibration is probably less than 50 miles over the years. It was primarily a ranch truck. The splines slide together easily. I have no reference on how easily they should go together. IF the castle nut is loose is wiggle expected?? Does the castle nut draw up the flange on a tapered seat?? By drawing it up tight I eliminated the vibration.

Since the root cause of the vibration was slop between the pinion and flange splines caused by a lose castle nut, I might have a solution. Loctite shaft sealant will lock those two parts together. The joint can be released with heat when rebuild time comes.

The worst outcome is trashing diff parts that I intend to replace anyway.........

This is what the community calls a ‘3rd member’ aka a ‘Differential Carrier Assembly’

Example, here is a pre-built assembly we offer @ Cruiser Outfitters

On your 1970, you have 4.111:1 9.5” semi-float differential assembly.

Your pinion depth and pinion preload are setup with shims, unless it’s been rebuilt as modern Toyota diffs and many/most rebuilds set the pinion depth differently (shim the inner pinion race vs bearing) and pinion bearing preload is set with a crush-sleeve. You can’t determine which method was used sans disassembly.

Now, do you need a rebuild? That depends on how much damage the bearings & gears suffered from that loose pinion preload and more importantly what caused it. Sure they can be tightened up and they ‘feel’ OK and may last another 100k miles. Or, the bearings are wearing, metal material is running through everything via your gear lube and it’s going to damage more over time. At a minimum I’d drop and inspect the fluid and pull the rear cover to inspect gears. You’re out a $8 cork gasket and diff fluid.

Still considering a self rebuild? We can absolutely help with any & all parts @ Cruiser Outfitters. Check out our FAQ on the subject:

Toyota Axle Re-Gear or Rebuild Information & Tech

Everything you need to know about the basic process of re-gearing your Toyota Land Cruiser front and rear differentials.

cruiserteq.com

Most common component is the R&P install kit:

Ring and Pinion Install / Differential Overhaul Kit - Fits 4x/55/6x Series Front & Rear Applications (IKTOYLC)

Toyota Land Cruiser Ring & Pinion Gear

cruiserteq.com

This kit includes to overhaul diff, and set pinion depth and pinion preload via shims or crush sleeve method. As you have a ‘stepped’ original ring and pinion set you ideally can reuse, the shims will be utilized.

 

[Scota4570]

It sounds like my next step is to drain the diff and check the oil. I am thinking I should search the oil with a strong magnet and see how much metal is in it. Also pull the cover and inspect the gears.

 

[franklin40]

even tiny metal flakes will show up visually through out the oil without a magnet (ask me how i know ) but it won’t hurt just in case. i think that’s the best next step for sure

 

[sogncab]

There's always some metal in gear oil it seems.

I keep my drain pans pretty clean just to inspect what comes out when I'm draining stuff, even just engine oil.

 

[charliemeyer007]

I think the drain plugs have a built in magnet - good design IMHO.