Diff is getting hot
Thread Starter
Intermediate
Joined: Sep 2002
Posts: 33
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From: Lancaster PA
Diff is getting hot
I just replaced the rear suspension. While the diff was out, I took off the cover to check for wear, but everything looked fine, so I replaced the side yoke seals and rear gasket and put it back together.
I drove about 20 miles tonight, then crawled underneath checking for loose fasteners, leaks, etc. and found the differential is hot, not burn-your-fingers hot, but definitely hot.
To be honest, I had not checked it before I took things apart, but there was no indication that anything was wrong. How hot should it get during normal operation? I expected it to be warm, but not this. What am I looking at here?
Oh yeah, there is fluid in it - 2 bottles of GM gear lube and one small bottle of GM positraction fluid.
I drove about 20 miles tonight, then crawled underneath checking for loose fasteners, leaks, etc. and found the differential is hot, not burn-your-fingers hot, but definitely hot.
To be honest, I had not checked it before I took things apart, but there was no indication that anything was wrong. How hot should it get during normal operation? I expected it to be warm, but not this. What am I looking at here?
Oh yeah, there is fluid in it - 2 bottles of GM gear lube and one small bottle of GM positraction fluid.
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Diff is getting hot (427street)
If you try the synthetic Mobil1 gear oil it should cool it down some. Maybe as much as 20 to 30 degrees cooler. The synth is that much better at reducing friction. And the friction is whats building the heat.
Thread Starter
Intermediate
Joined: Sep 2002
Posts: 33
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From: Lancaster PA
Re: Diff is getting hot (Jvette73)
I didn't think about synthetic at the time. Do you still need to add the small bottle of positraction additive or would it be incompatible with synthetic.
In any case though, is it normal for the diff to get hot?
In any case though, is it normal for the diff to get hot?
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
Re: Diff is getting hot (427street)
The Mobil1 additive claims to work just fine w/ LSD, so I would assume no additive necessary. I added Mobil1 to my friend's 1990 300ZX (LSD) and it did just fine, no chattering.
-Steve
-Steve
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Re: Diff is getting hot (427street)
Probably nothing to worry about. The heat that is. The diff is going to get warm under normal use just from the internal friction warming things up. If it gets HOT hot, I'd be more concerned.
btw, I'd still put the posi additive in regardless of what fluid you have. But damn that stuff smells BAD! :U
btw, I'd still put the posi additive in regardless of what fluid you have. But damn that stuff smells BAD! :U
Burning Brakes
Joined: Sep 2001
Posts: 1,166
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From: Tulsa Ok
Re: Diff is getting hot (ROD NOCK)
Unless you have side pipes, the exhaust runs underneath the differential. That tends to warm things up. Doh! You do have sidepipes. NEVERMIND....
[Modified by FeedVaal, 12:44 AM 8/13/2003]
[Modified by FeedVaal, 12:44 AM 8/13/2003]
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Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Diff is getting hot (427street)
Yes, the differential will get hot during normal use. This is one of the reasons flywheel horse power and rear wheel horse power are different. The 12-15% power you loose between the two measurements is typically lost in heat. Consider how many BTU's of heat equal the approximately 80hp I lose from flywheel to the rear wheels. If you were to really work the engine, both the trans and the rear end will get very hot. Racing cars often use oil coolers for their rear ends. I believe my ZO6 also has an oil cooler for the rear.
Chuck
Chuck
Melting Slicks
Joined: Nov 2001
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From: Eastern US XX
Re: Diff is getting hot (427street)
I rcently changed my '69 over to Mobil 1 and I DID use the bottle of GM additive. Made a huge difference - really quieted things down (also didi my 4 speed at the same time - shifts real nice).
Thread Starter
Intermediate
Joined: Sep 2002
Posts: 33
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From: Lancaster PA
Re: Diff is getting hot (427street)
OK, after the feedback from everyone, I began to think I was overreacting so I took it for a longer drive tonight - 1/2 hour drive at highway speeds. Now its HOT HOT. Too hot to touch. This can't be normal can it? And what would cause it?
I am getting no unusual vibrations or noises - at least not yet.
I am getting no unusual vibrations or noises - at least not yet.
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Re: Diff is getting hot (427street)
I think one or more of us needs to go for a drive and feel the diff when we get home. I really doubt that you have a problem if everything otherwise seems fine.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Diff is getting hot (ddecart)
I know the transmission under the console of my Z makes anything in the console compartment above very hot. I can imagine how hot the transaxle must be, even in normal driving. Energy cannot be consumed or expended without heat. Even a 5 hp drive train loss produces heat equal to almost 13,000 BTU's per hour. This is just about what it would take to boil 100 pounds of water (12 gallons) starting at room temperature.
Chuck
Chuck
Pro
Joined: Jul 2000
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From: Now Frozen in Michigan
Re: Diff is getting hot (427street)
This heat does sound extreme, but I may be wrong. Two low cost methods I would use would be to wrap the exhaust in the diff area, and change the diff lube out to M.1.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Diff is getting hot (ROD NOCK)
Mine gets so hot during spirited driving that you can't touch it for a long time after shutdown.
I've considered adding a oil cooler. My problem is 4.11 rear gears lots of hp and big tires. The pinion runs at very high rpm (7000+rpm). I use valvoline synthetic Multi weight. something like 100w 130. one tube of posi and 8 ounces of Energy Release friction inhibitor
I've considered adding a oil cooler. My problem is 4.11 rear gears lots of hp and big tires. The pinion runs at very high rpm (7000+rpm). I use valvoline synthetic Multi weight. something like 100w 130. one tube of posi and 8 ounces of Energy Release friction inhibitor
Thread Starter
Intermediate
Joined: Sep 2002
Posts: 33
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From: Lancaster PA
Re: Diff is getting hot (427street)
I tried a few things this week and thought I would post an update. I finally got a chance to compare my car with another vette.
You guys were right. The diff just gets that hot during normal driving - I never noticed before. In any case I did change to Mobile 1 synthetic. It still gets hot, but the synthetic makes a noticable difference. I did not add the tube of positraction additive, but I am getting some chatter, so that is my next step. Otherwise everything appears to be OK.
Thanks for the feedback.
You guys were right. The diff just gets that hot during normal driving - I never noticed before. In any case I did change to Mobile 1 synthetic. It still gets hot, but the synthetic makes a noticable difference. I did not add the tube of positraction additive, but I am getting some chatter, so that is my next step. Otherwise everything appears to be OK.
Thanks for the feedback.