C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Transmission fluids

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Old Apr 28, 2005 | 06:31 AM
  #1  
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Default Transmission fluids

I am planning to change the fluids in the manual gearbox and differential in my '92. However my Haynes manual talks about an overdrive unit so I am confused. Can anyone tell me how many places I need to change oil, and which type?

Also.. I have what seems to be a leak towards the rear of the gearbox. There is some very clean oil in the location of the exhaust mounts (at the gearbox) and what seems to be 'splashing' around the tunnel at the rear of the box. Is this normal?

Thanks!
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Old Apr 28, 2005 | 08:37 AM
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From: Stamping Ground KY
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The 1984-88 manual had a 4+3 gearbox that is a 4 speed with an overdrive gear bolted onto it (hence the +3), perhaps your haynes manual is referring to this?

Your ZF6 has two plugs, one on the bottom for draining and one on the side for filling. It requires a 17mm hex head wrench (you should verify this yourself) that you should be able to buy from sears.

Remove the side plug 1st!!! If you drain the thing and find out the side plug won't break loose you're in trouble!

I believe the requirement for the transmission is straight 30 weight oil; but you should probably get more verification on that.

I have the same clean oil leak. I'm not sure what it is and it does concern me.

I've never looked into filling the differential before so I'm no help there...
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Old Apr 28, 2005 | 09:48 AM
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I'm getting ready to do these both on my 92. JCD is correct, 17mm hex driver. They are a little difficult to find so start searching now.. advanceautoparts.com has them for $5 or so. They are usually listed as VW Drain Plug Tool. I was only able to find a 17mm hex wrench at Sears.

ZF-6 factory fill is 10W-30 dino oil. Many people have switched to BMW/Castrol 10W-60 (M5 engine oil) fully synthetic. I'm heading over to the BMW dealer to pick some up today, $8 a bottle. ouch.

You can get a pump to suck the diff oil out of the case, or purchase a drain plug kit and drill it. I'm going with the pump this time, not feeling to confident in drilling a perfectly good D44 case.

OH, don't forget to use 2 bottles of limited slip additive in the diff..

Last edited by ztrips; Apr 28, 2005 at 09:56 AM.
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Old Apr 28, 2005 | 10:39 PM
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From: Enterprise AL
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Several on this forum (me included) have used Redline MTL in the ZF 6-speed. I just spent $2600 on a new tranny as the old one LOCKED UP while driving!! My local transmission guy opened it up and said it appeared to be a lubrication related failure. We can't say for sure if it was the fault of the Redline oil, but it was at least a contributing factor. So for me, the new ZF will only get the GM 5-30 transmission fluid, and I will be sure to change it every 10-15K miles!
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