dual questions. o2 sensor and rear diff fluid change.

[SMKN97GP]

is changing the rear diff fluid hard on an 81? there isnt a nice plug on the pumpkin somewhere that i can drain it out of right? mostlikely im gonna have to take off the cover, if thats the case from the look of the chiltons manual there is a big piece over the cover like a giant brace spanning across the rear end, is that a PITA to remove? it looks like it would be alot bigger job than say changing the rear diff fluid on an 87 camaro?


second, next tuesday im going to my buddys shop to do some work and we are doign exhaust stuff. if i remove my cat, there should be no negative effects right? because the 02 sensor is before the cat. and if i wanted to go true dual, would it be ok to have just one 02 sensor on the ride downstream and none on the left? i know some of you other 81 guys out there have heavily modifiee exhaust so im wondering how you did it.

 

[Bob Chadwick]

For $10 or 12 bucks you can buy a small pump that will suck the fluid out of the differential through the fill whole. Make sure you get the posi-lube when changing it.

 

[SMKN97GP]

i have a siphon pump i guess i can use that. thanks

 

[UKPaul]

Removing the cat will have no effect on the O2 sensor at all. Mine had a "test pipe" in place of the cat when I bought it & it ran OK. I fitted MA true duals which had the O2 sensor in the d.side in about the same position as stock. That worked OK as well. Then I made my own true dual system & bolted it up to a set of Dynomax ceramic coated Headers. Summit sell reducers for Headers (3" down to 2 1/2") that have an O2 sensor fitting in them. I mounted the O2 sensor in the reducer on the drivers side. I was warned that I could be heading for trouble as the sensor may not get hot enough while idling, but it's working well. I think the ceramic coating on the Headers may help to keep everything hot inside. You don't want to locate the O2 sensor further downstream than you have to, as they need to get up to temp before they start working correctly. If you do have problems in the future with a sensor not getting hot enough then you could fit a heated sensor. You shouldn't need to do that as mine is as far downstream as anybody need put one & works well.

Fitting true duals to my '81 was the biggest seat of the pants power increase I've had. You should be able to buy a system eg MA, that has a sensor fitting already in place or, if you're getting a custom one made, a bung can be bought which can be welded onto the pipe to allow the sensor to be fitted (once a hole has been drilled for it!). I can't think of what you'd gain by locating a sensor toward the rear of the system, I've just kept mine as close to the stock position as I can.
Paul

 

[SMKN97GP]

well with hearing that i think im gonna go with no cat, true duals and just put the sensor on the stock position on the right side and hopefully it will work out ok