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Old 01-22-2006, 12:08 PM   #1
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TC4 Diff gets tight when warm?

I've noticed that the rear diff on my tc4 seem to be tighter at the end of a race. After cooling down for 10 minutes it returns to a normal pressure.
I rebuilt and shimmed, nothing looked grooved or worn, and the diff was smooth, it just gets tighter when warm. After the rebuild it was OK for 4-5 runs then started getting tight again. The front (which is steel) doesn't have this problem, and I generally have the front a bit tighter than rear. I'm using the stock greases and silicones, replaced balls, washers, thrust assmbly. The problem persists. I'm running stock, rubber, on carpet. So I'm wondering.

#1. Is HEAT the problem?
#2. Should it be getting warm in the first place?
#3. Do steel diffs never do this?
#4. Do I need more Locktight on the nut?
#5. Should I buy an x-ray?

Thanks for any help you can offer,
Bigair
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Old 01-22-2006, 12:34 PM   #2
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I have some questions. How much tighter is the diff getting after a run, does it get like really really tight compared to at the start, and is it possible that it is slipping?

It would make sense that heat would be the problem because as the balls roll (or slip) they are generating heat which leads to expansion, which could cause the tightness.

Depending on how tight you have it set up to start out with. You should have it the loosest you can without it slipping.

Steel diffs are probably a little more precise than plastic outdrives (you are running plastic on the rear, right?

Locktight probably wouldn't solve the problem but go for it.

Definately buy an X-ray, especially if you want to have to wait 2 weeks for parts or have a cars-worth of spares with you.
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Old 01-22-2006, 01:04 PM   #3
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The Plastic diff gets about 30-40 percent tighter when warm. When it's cool, the diff is tighter than most others, but it needs to be or else it slips. The metal diff in front is a little more free. My Pro4 diff is way looser without slipping at all. I've had diffs get LOOSE before, seems to be failure mode when the nut slips... but never tighter, until now.
Maybe a better grease would help?
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Old 01-22-2006, 01:13 PM   #4
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Just out of curiosity what diff balls are you running? Im running ceramics and I can have my plastic tc3 diffs pretty loose with no slippage. I have never noticed your problem in my diffs so I can't say for sure it would help but for an extra 10 bucks to boost performance can't be beat. I would say take apart the diff and spray out with motor spray and use plenty of stealth diff lube when rebuilding.
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Old 01-22-2006, 02:28 PM   #5
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i also had trouble with a plastic diff in my TC3. I always had trouble with my rear diff and not with the front one,also when i switched them.If i where you then i would put the steel diff in the rear and the plastic in the front because the rear diff has got to work harder then the front one.

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Old 01-22-2006, 02:56 PM   #6
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Generally the rear diff gets more abuse than the front, so it will heat up faster. I had the same problem with the TC4 - the outdrives get warm and expand. Running mod they will actually melt. I used the IRS lite-drives on the car, which fixed most of the diff problems. They are aluminum outdrives, although I imagine the AE steel outdrives would have the same effect.
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Old 01-22-2006, 03:36 PM   #7
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ive ran TC3's for about 4 years and never had a problem with a diff...the diffs were all the stock parts that came with the kit...

i dont know about the rear diff getting more abuse...i would think the front would...can you give me some reasons why the rear gets more stress on it?
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Old 01-22-2006, 04:34 PM   #8
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I would say on tight turns sometimes the inside rear is picked up (or severly close to it) and causes the rear diff to unload to the wheel with lesser traction (the one in the air) causing the balls to spin fast thus creating thermal energy which in turn expands stuff and it gets tight.
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Old 01-22-2006, 05:41 PM   #9
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I'm running stock balls and rings in the plastic rear and the metal front. I agree the metal outdrives seem to work better, but why? Cuz they're on front? Since the metal outdrives have nothing to do with the bearing surfaces siezing up, how would they be better? Does the metal dissipate heat better?

As for which diff gets most abused, The rear _does_ lift while turning.
On the other hand, the front see's bigger swings in grip, compression, and turning radius, so which one is working harder? I dunno...

I just now rebuilt the rear again with new washers, and thrust washers but I used the old balls as the diff is nice and SMOOTH, it just has a tendency to lock up a little. It still seems like there's not much margin between too tight and slipping, like maybe 1/4 turn.
I won't be able to test at the track again till later in the week.

I did notice some bearing oil was flung onto the stealth lube, could that be a clue?

Thanks for the help,
bigair
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Old 01-22-2006, 06:20 PM   #10
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do you have bushings in the diff or bearings? if i remember correctly the steel outdrives use bearings and the plastic ones use bushings
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Old 01-22-2006, 06:39 PM   #11
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You say you have replace just about everything else in the diff but the outdrives. When i ran my tc4 i did experiance the same problem you have. I think it was the raised portion that captures the diff ring is to tall and when it expandes it binds on the gear try a new set of outdrives and if that doesnt do it carefully sand down the raised area and that should take care of it.
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Old 01-23-2006, 01:19 AM   #12
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Quote:
Originally Posted by HVFracingwilly
You say you have replace just about everything else in the diff but the outdrives. When i ran my tc4 i did experiance the same problem you have. I think it was the raised portion that captures the diff ring is to tall and when it expandes it binds on the gear try a new set of outdrives and if that doesnt do it carefully sand down the raised area and that should take care of it.
This brings back some memories...I think I actually continued to have problems after switching to the IRS diffs...eventually figured out that the diff gear itself was too thick in the center (where the diff balls are captured), and would expand and rub on the diff rings. I had to have the diff rings machined to take away some material. I think AE sent out replacement diff gears a few weeks after I got fed up with the car and sold it.

If your car is one of the earlier kits, the gear could be the problem. Or, as Willy said, maybe the inner D-shaped portion of the outdrives is the issue. If your car wasn't in the first few batches, I'd just replace the outdrives with metal parts. Move your steel outdrives to the rear, and perhaps get some aluminum outdrives for the front.

As far as the rear diff wearing faster than the front, I'm simply basing this off the fact that my rear diff always, without fail, wears faster than the front diff. From this I am inferring that it is worked harder in cornering.
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Old 01-23-2006, 01:41 AM   #13
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I'm with the heat expansion theory...

But what does diff tightening got to do with getting an Xray?? And why an Xray?? The T2 look like a detuned 415 MSX...I like the T2's machined alu stuff...But I can't accept the fact that a top of the line kit come with PLASTIC shocks....
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Old 01-23-2006, 06:50 AM   #14
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I ve experienced this often on my tc".. When i switched to the lightened steel version, the problem disappeared completely..
I run mod so this was really visible
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Old 01-23-2006, 07:56 AM   #15
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Thanks for all the help everyone!
Speedo, the diff ring capture ledge could be it. This might also explain why it feels tighter than normal when static. Although, I didn't see any wear on the gear or the face of the outdrive. I'll file the d ring retainer face, or replace with steel after I try one more time, maybe with a new gear also.
Although the balls feel nice and smooth, I'm wondering if they can wear down enough to cause binding between the gear/Face? (and still be round)

Ben.C the x-ray was a joke.

Or is the TC4 a joke.............. I'll let you know....

"bigair"
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