True-Trac Chatter?

[TRC51]

Guys,

So I recently upgraded my rear diff to a 31 spline True-Trac and moser axles (based on the recommendation from my mechanic). I was feeling pretty confident of the decision based on the posts here, but now i am lost.

Previously my car had the stock diff in it, but it was making some rubbing noises in the rear end for a long time. I never had problems with it, but it was annoying. I recently decided to fix it because it started to get worse. That's when the true-trac was put in. Here's what happened:

My mechanic put all parts in and gave me back the car. Now when I turn left or right and apply power, I get a chatter from the rear end. Not a lot of power, just normal driving. Sometimes it will chatter a little when I take off going straight, but that seems to be more rare. I took the car back to him because it just didn't seem right. I found out that he put synthetic in it (stock fluid I guess), which now I read is a mistake. So when I gave the car back to him he switched it back out to mineral oil (per Detroit's recommendations). I have been driving the car for about 30 miles or so now and I have seen almost no improvement. Driving the car to work this morning it was almost irritating.

That said, could I be seeing tire hop now? I never had it at all before, so I have no idea if this is similar.... but I really doubt I am feeling tire hop with so little power being put down at the time I feel the problem. And it actually lessens when I go for more power and start spinning the tires. The car is also really loose now. If I apply any power in the corner, the car loses traction and kicks out.

What do I do now? To note, my mechanic will do whatever I ask him to do to make it right, so I am not looking to say that the mechanic is out to screw me. I just want to make the car right so I can enjoy driving the car again.

Thanks in advance.

Travis

 

[skwerl]

What gear lube did he use? Synthetic is a non-starter with the Tru-Trac, you MUST use a mineral oil. These days you have to really look for non synthetic, I used Lucas in mine.

And I do seem to recall a little bit of chatter in mine for the first few days but it went away within a couple hundred miles. Break in possibly?

 

[Marble]

I would give Eaton a call and ask what would happen if you ran synthetic in the differential upon installation.

After Redding their website I did not see anything that said the unit would be damaged with synthetic oil.

 

[Boaisy]

I first tried Torco (non-synthetic) in mine, but had better noise results with Lucas. There is a known chatter with some of the TrueTrac's when there ISN'T load applied, but not sure about when load IS applied. The issue I had with mine was, for instance, coasting down a hill with the car in neutral (or clutch pushed in), the rear end would sound almost like tank tracks. One you applied load to the drive train, the chatter went away.

Other people of SVTP noted of the same sound in their's. Eaton told the people it was an expected noise by the design of the diff. Essentially, it is a backlash/clashing from the planetary gears when there isn't a load applied on the drive line. Apparently certain vans use the same part # for the TrueTrac and the noise is a lot worse in those. Some people were lucky enough to either not hear it, or had a unit that didn't produce any noise at all. I have not heard about automatics having this kind of noise, just manuals.

 

[TRC51]

What gear lube did he use? Synthetic is a non-starter with the Tru-Trac, you MUST use a mineral oil. These days you have to really look for non synthetic, I used Lucas in mine.

And I do seem to recall a little bit of chatter in mine for the first few days but it went away within a couple hundred miles. Break in possibly?

Original lube he used was the stock fluid recommended from Ford (put maybe 20 miles on that). The replacement fluid is the 80W-90 Valvoline recommended by Detroit/Eaton. I don't have a lot of miles on the new unit, but would be nice if it went away with some break-in. The service rep my mechanic talked to at Eaton stated it shouldn't be doing it.... and my mechanic has one that doesn't do it.

I would give Eaton a call and ask what would happen if you ran synthetic in the differential upon installation.

After Redding their website I did not see anything that said the unit would be damaged with synthetic oil.

Eaton said the synthetic should not have damaged the unit permanently. I thought of the same thing.... and I guess it has happened to others that have not had a problem once it was replaced.

I first tried Torco (non-synthetic) in mine, but had better noise results with Lucas. There is a known chatter with some of the TrueTrac's when there ISN'T load applied, but not sure about when load IS applied. The issue I had with mine was, for instance, coasting down a hill with the car in neutral (or clutch pushed in), the rear end would sound almost like tank tracks. One you applied load to the drive train, the chatter went away.

Other people of SVTP noted of the same sound in their's. Eaton told the people it was an expected noise by the design of the diff. Essentially, it is a backlash/clashing from the planetary gears when there isn't a load applied on the drive line. Apparently certain vans use the same part # for the TrueTrac and the noise is a lot worse in those. Some people were lucky enough to either not hear it, or had a unit that didn't produce any noise at all. I have not heard about automatics having this kind of noise, just manuals.

This is not gear noise or whine. It's actually pretty quiet. The problem is that it seems to be... I guess what I would consider "binding". It feels like it's not interfacing the way it should. The car is spinning both wheels and laying down power. It's just jumping and skipping a bit at times.... particularly when turn sharply (primarily in 1st gear and just starting away).

I have no problem accepting the unit if it's "normal" and will eventually break in. What I don't want to do is accept it for what it is and it never goes away, especially if it's a faulty unit.... because I really do not enjoy driving the car right now.

 

[Boaisy]

Yeah, my unit never had issues when it came to applying the power, even during break-in. If anything, it was pretty solid. When I had upgraded the suspension and wheels/tires for the track, it was like a go-kart around corners with that unit.

Like you said, if it goes away it should be fine, otherwise, I would get the unit itself checked out.

 

[JUSTA3V]

Mine as well. Has been silent since day 1. On the street and over 100 track launches on slicks.

 

[nawagner]

I've had no problems like this with mine either.

 

[Marble]

Mine has always been quiet. But I haven't changed the fluid in a few years which is like 7-8k miles.

 

[Pentalab]

I hear just a tiny bit of whine on my automatic.... but only when coasting up to a stop sign. Dino oil used since initial install.

BTW, how often is it to be changed ?? I had the WL watts link installed the same day as the Tru-trac. The WL differential cover comes with drain + fill plugs, so draining and putting new dino oil in should be fairly easy.

To the OP, did you change gears, or have issues with oem rear crown /pinion gears, binding, alignment etc. The tru-trac may be exasperating any rear gear issues

 

[hunter1022]

I have had the True Track for about two years and when first installed my Bone Headed mechanic put in Synthetic Gear Oil even after i i told him not to i was to pissed to have him change it (did not trust him) anyway took it home and installed Lucas 80W90 Dino Oil after draining it has not made a sound so far. From what Eaton says in there info is Synthetic oils are not recomended it just won't work the way it is supposed to but won't kill it so if you got the Dino Oil in after you drained the Synthetic it should work fine. If its making noise all the time and not just an occasional click or clunk on a sharp turn something is wrong.

 

[TRC51]

To the OP, did you change gears, or have issues with oem rear crown /pinion gears, binding, alignment etc. The tru-trac may be exasperating any rear gear issues

No change in gears. Still running the stock 3:73s. BTW... thanks for your PM. Sorry I never replied... but I was just so dumbfounded that you completely changed my thought process and plan, I forgot. LOL

I have had the True Track for about two years and when first installed my Bone Headed mechanic put in Synthetic Gear Oil even after i i told him not to i was to pissed to have him change it (did not trust him) anyway took it home and installed Lucas 80W90 Dino Oil after draining it has not made a sound so far. From what Eaton says in there info is Synthetic oils are not recomended it just won't work the way it is supposed to but won't kill it so if you got the Dino Oil in after you drained the Synthetic it should work fine. If its making noise all the time and not just an occasional click or clunk on a sharp turn something is wrong.

So are you saying that the occasional chatter and clunk on a SHARP turn is something that happens with these? If you are driving straight down the road and laying power down, I almost never feel it and the car puts down some soft dark patches of tire, so I know it's grabbing. Originally when I felt it pulling away from the shop, it was half on a sidewalk and half on the pavement, so I was wondering if that was part of the issue. It was also very apparently under light load during SHARP turns. Like I said, I almost wondered if it was tire hop on a tight diff.

AS AND UPDATE:

I drove the car in warmer weather yesterday and was very surprised to see that the chatter was not present. The car was driven lightly (kids in the car) for about 15 minutes and then parked for a couple hours. I then drove the car for about 30 minutes and put it through some paces.... and the problem seems to be gone.

My initial thoughts are that the first drive after getting the fluid swapped did not quite get all the synthetic worked out of it, but now the second drive has the diff working on the mineral oil that was put in..... so I am HOPING I am good to go.

I am going to wait for cooler temps tomorrow and give it another go.

 

[Boaisy]

I hear just a tiny bit of whine on my automatic.... but only when coasting up to a stop sign. Dino oil used since initial install.

BTW, how often is it to be changed ?? I had the WL watts link installed the same day as the Tru-trac. The WL differential cover comes with drain + fill plugs, so draining and putting new dino oil in should be fairly easy.

To the OP, did you change gears, or have issues with oem rear crown /pinion gears, binding, alignment etc. The tru-trac may be exasperating any rear gear issues

I changed mine within 500 miles of installation from Torco to Lucas (to help with the noise). Never changed it after that, and probably had close to 40k-50k miles on that oil. I don't see any official recommendations from Eaton, nor any on forums about proper change intervals. Even with the WL Watts Link, which I had, I would invest in a easy fill tool for the gear oil. It can get messy without one.

 

[TRC51]

Update:

I am back from vacation and talked with my mechanic today. He mentioned to me while I was on vacation that he was putting in another true-trac for a customer with an F350 (proving he does these all the time). I just got off the phone with him this morning and the F350 is having the same problem.

That said, he is putting in another call to find out what it going on and will inform Eaton that he will not put another unit in until they can clarify what the issue is. Well.... we may swap mine out with a replacement to see if the problem persists, but he will not recommend another until they can come clean on the existing units.

Waiting on his call to tell me his path, but if we do decide to go with a replacement, and it also has this issue... we may be considering a clutch type.

Thoughts?

 

[Badd GT]

I just had a tru trac installed 2 weeks ago after i blew up my Eaton posi at the track. Mine is whisper quiet and I couldn't be happier. Lucas oil in mine. East coast gear supply in Raleigh. Look them up, very impressive operation, they have a tech line.

 

[808muscle]

I have had the normal clip clop coasting at slow speeds to a stop. Power through the turns has been there since day one. My first unit did break apart and was replaced under warranty. They only noise was a very bad whine. Second unit has 300+ runs down the strip with no issues.

 

[Sky Render]

Just to confirm everything this thread has said:

1. The design of the Eaton TrueTrac is very similar to that of the Torsen T-2. It is a worm-gear-type differential (as opposed to clutch or viscous).
2. Do not use synthetic gear oil or friction modifier. Synthetic oil is "too slippery" and will lower the effective bias ratio of the unit. I use Lucas 75W-90.
3. Some (not all) TrueTracs are noisy on deceleration, especially coming to a stop. The noise is similar to the "clacking" noise that a tracked piece of construction equipment makes. This is caused by gear backlash in the unit, and is more noticeable on automatic cars because when decelerating they shift down through every gear.

I wrote an article on the TrueTrac awhile ago, if you'd like a bit more in-depth tech:
http://www.motoiq.com/MagazineArtic...art-5--Putting-the-Power-Down-with-Eaton.aspx

 

[TRC51]

Just to confirm everything this thread has said:

1. The design of the Eaton TrueTrac is very similar to that of the Torsen T-2. It is a worm-gear-type differential (as opposed to clutch or viscous).
2. Do not use synthetic gear oil or friction modifier. Synthetic oil is "too slippery" and will lower the effective bias ratio of the unit. I use Lucas 75W-90.
3. Some (not all) TrueTracs are noisy on deceleration, especially coming to a stop. The noise is similar to the "clacking" noise that a tracked piece of construction equipment makes. This is caused by gear backlash in the unit, and is more noticeable on automatic cars because when decelerating they shift down through every gear.

I wrote an article on the TrueTrac awhile ago, if you'd like a bit more in-depth tech:
http://www.motoiq.com/MagazineArtic...art-5--Putting-the-Power-Down-with-Eaton.aspx

All good info. However, I have to clarify again:

This is not a noise. This is chatter, or what you could call a shudder when taking tight turns in either direction, even with low to normal power input. I also experienced it driving straight away from my mechanics shop while one tire was on a sloped concrete sidewalk/apron and the other tire was on pavement (the entrance across the sidewalk from the street). This make sense because of the two different surfaces.

My aftermarket shifter makes more noise... and that is not very much at all.

 

[TRC51]

Just got off the phone with Detroit earlier today....

Does anyone else in here think this is "normal"? While the guy at Detroit says it shouldn't be something that happens, he finished by saying that I will likely have the same result if I put another truetrac in there. I don't understand. The guy said maybe I should consider another diff.... not what I expected to say the least.

 

[TRC51]

UPDATE:

Switched out the diff for an Eaton Carbon Fiber 31 spline unit and the chatter is pretty much gone. The car even drives the way it should now and all seems good in the world again.

To be clear, we have no idea if this was the Truetrac unit that failed or some other scenario. However, considering that my car will never likely break into the 700+whp range, I am definitely pleased with the driveability of this new carbon fiber clutch unit. This car will never be focused on just racing, so I decided to go with an upgraded clutch diff in an effort to get the driveability back.... and it seemed to work.