Problem - front Trutrac diff or CV joint?

[Mike_Rupp]

Its not the tire pressure as much as tire pressure relates to tire height. If the tire height is different the internals of the differential are going to be moving around a bunch more than normal. Thia can overheat the gear oil, which can eventually damage any differential.

 

[barshnik]

Mike - funny you should mention that...

I normally air down whenever off road (which is most of our Disco usage), to 15 psi (measured).

Here are the latest findings:

TT is out and inspected. Despite what Alan reported earlier (sorry, Alan) there were no metal bits found, although Bill (mechanic) was certainly making an effort to find some while you were there (so I see where you got that impression.)

What he did find were some unusual wear patterns on TT gears (sorry, I don't know a ring from a pinion, I'm embarrased to say), as well as some gear discoloration which may indicate it overheated at some time. He is not sure what to think - we are waiting for Bill from Great Basin to return Tue. of next week so he can determine if any of this is 'normal' for a TT with 10k miles on it. At any rate, a new one will be going in late next week if all goes well.

When I dropped off the Disco to Bill (the independant LR mechanic Bill), the Disco made speed-dependant loud metalic clicking - no, clanking - sounds when turning either direction, only in reverse. Not so much as a peep out of it when turning while driving forward. The noise was louder than I've ever heard a CV make (I've had front wheel drive cars for 30 years, and have heard a few...) and of a different character - much more loud and metallic clanking sounding, and definately coming from the diff, so something is not right with it, we just don't know what yet, and probably won't till Bill at GBR gets it back.

Noise only when in reverse, and turning 2/3 lock or more (TT would be working to act as 'open' at this point, although why only in reverse I have no idea.

Axles splines show no signs of any wear or damage at all.

I'll keep you posted.

John F
LV, NV

 

[D Chapman]

Wear on the TT gears or the ring and pinion gears???

If I were to bet, I would say the ring and pinion...Which means the TT was installed wrong. Well, at least you hope so. 3.54:1 gears are cheap. A new TT may cost some..

 

[Steve Rupp]

I've seen plenty of dark colored diffs. If it really overheated the bearings should be stained brown. Some brown stuff that rubs off is not a huge deal.

Please tell me Bill is going to pull the boots off the CV's as long as this truck is apart. A new clamp for the boot costs nothing. Make sure he pulls apart those CV's and see if they are indeed OK. I'm still not convinced it's in your diff. If you're not driving thousands of miles on the highway with tires inflated differently, it's not going to screw up a diff. A TT is very forgiving. Have you ever had a front tire off the ground with the CDL unlocked and no traction control? It spins like an open diff and makes no clinks, clanks, or growns. I would still like to see those CV's.

 

[D Chapman]

I don't know Steve....My TT has make some nasty nosie if I get one wheel in a tight spot, and the other is off the ground or in low traction...Nasty...

 

[barshnik]

<<Please tell me Bill is going to pull the boots off the CV's as long as this truck is apart.>>

I'm sure it will cost more than 'nothing', but Monday AM I'll call Bill and have him disassemble, inspect, and re-grease both CV's just for the peace of mind - I do make occasional water crossings, even here in the desert.

Does it make sense to replace the boots with new at this time, even though they look fine and undamaged?

Can you speculate on why the noise (if caused by either TT or CV) would only occur driving in reverse (while steering at more than 2/3 steering wheel lock)?

When I dropped off the truck, the noise in reverse while turning either direction was a loud 'clanking' sound, very metallic. Seemed much louder and more metallic than I remember CV noise being (I've driven front-wheel drive cars for 30+ years, and have had some bad CV's) I drove and he listened, and visa versa, and the loud noise sure seemed to come from the diff - quite apparent, though I know funny things can happen with noise transmission when metal connects everything.

Thanks for your help, Steve and others.

John F
LV, NV

 

[Steve Rupp]

Dan, I know what you're saying. Mine has done that too but has only done it when i'm in real nasty situations. I'm not convinced that it wasn't the fan hitting the shroud. This was before I replaced my motor mounts.

The other day though, I got on a pretty big rock out here to test out my new tires and rubbing. I put the rear tire on the rock with the diff unlocked. I pulled the front tire off the ground and was able to lock up the other side using the brake. When I let off the brake, the tire would spin freely without any noises. This guys noise just sounds so much like a CV that i'm running out of ideas.

Oh by the way, I'm with you on the whole power distribution and center diff argument. In that situation, there was NO power going to the rear. It was all up front, just like when I drive down the road. Theory doesn't always prove true.

 

[D Chapman]

Yea, if I let off the brake, the wheel will spin freely...But, If I'm brake/modulating the TT will groan....

I think dudes noise is still the CV(s)....But, I have not seen the truck...

 

[Mongo]

if the gears are fucked, pinion bearing would be my guess...or the cv's...

 

[Milan]

Yea, if I let off the brake, the wheel will spin freely...But, If I'm brake/modulating the TT will groan....

I think dudes noise is still the CV(s)....But, I have not seen the truck...

Mine does that too after years of abuse. I figure it's a bit worn and the noise is the worm gears jamming against the case. But it keeps on ticking.

I'd be inclined to think CVs also, as I have never heard a TT "click". But we'll have to wait and see.

 

[barshnik]

I agree that CV's 'tick' or 'click'. The noise I've got, however, is loud 'clanking' along with a little scraping. CV's will be ruled out (or in) tomorrow, hopefully.

How about a time estimate to disassemble / inspect / reassemble each CV so I'm not blind-sided tomorrow? Thanks,

John F

 

[Steve Rupp]

There are 2 clamps on each CV boot. They will cut them off and pull the boot. The CV's will have to be cleaned a little to get the grease off, but they will need to put new grease in anyway. It really isn't a big deal. If your diff is out, then the axles are sitting on a bench somewhere. You will just need to pay for 4 clamps and CV grease. It really shouldn't be a big deal. Maybe an hour of time??? Like I said though, as long as they're out, it would be dumb not to check them out.

 

[barshnik]

There are 2 clamps on each CV boot. They will cut them off and pull the boot. The CV's will have to be cleaned a little to get the grease off, but they will need to put new grease in anyway. It really isn't a big deal. If your diff is out, then the axles are sitting on a bench somewhere. You will just need to pay for 4 clamps and CV grease. It really shouldn't be a big deal. Maybe an hour of time??? Like I said though, as long as they're out, it would be dumb not to check them out.

Ordered up the CV disassembly, inspect, reassemble (if OK) with new grease, boots, and clamps today.

I'll let you know what (if anything) they found, tomorrow...

John F
LV, NV

 

[Steve Rupp]

I hope Bill is as thorough as he is slow. I'm dieing to know what's wrong.

 

[barshnik]

<<I hope Bill is as thorough as he is slow.>>

I made the tactical error of telling him I was in no big hurry. Should at least know the condition of the CV's today.

John F
LV, NV

 

[barshnik]

Well, the CV's look perfect, so sign of wear or damage at all. Sparkling clean, beautiful. They are getting put back together today with new grease, boots, and bands.

Now waiting for a replacement front TT from GBR. Bill at GBR said he has been selling TT's for many years without a failure, now in the last couple of weeks he has had 2 other units fail just like mine. Keep in mind only 10k miles on mine. Maybe a bad batch? I'm sure it'll be a long time before hearing from TT about what went wrong, but at least the truck will be running again...

John F
LV, NV