madkaw Posted July 28, 2009 Share Posted July 28, 2009 This might be showing my ignorance, but how hot do stock diffs get. The reason I ask is because I noticed when cruisin some highway miles with my 81 280zxt and I can actually feel heat on the floor inside the center console. I figured it was my catalytic converter getting hot ,because it is probably the original and is probably getting plugged up(replacement exhaust is in the works). Anyhow, my daughter came back from a 50 mile highway cruise and she pulled into the driveway and you could here my new walbro really whining, which it never did before. I broke out the pressure guage to check pressure since I had a previous pressure problem, and the pump checked out, but still was whining. When I went to diconnect the power to the fuel pump I notice that the fuel tank was very warm-almost hot. I got under the car and started snooping around and I grabbed the diff and it is red hot to the touch. It is hot enough to warm up my fuel tank and I think bake the fuel line above my Walbro-the rubber line was feeling pretty mushy for a new line. Can this be normal??? I checked the gear oil level and it is where it should be. The car drives okay, but I think the gas mileage on the highway should be better. The gas mileage is 19-20 mpg in the city, but it isn't any better on the highway. Am I over reacting here, I guess I have never grabbed a diff to check the temperature after a cruise. The exhaust muffler, catalytic and pipe were all cooler then my diff. i realize it would hold the heat longer, but it still seems way to hot for just some highway cruisin. Quote Link to comment Share on other sites More sharing options...
MAG58 Posted July 29, 2009 Share Posted July 29, 2009 I'd safely say that's a little warm. How long has this been happening? Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 29, 2009 Author Share Posted July 29, 2009 By the way, I forgot to mention that the car is an automatic. I haven't had the car very long and have only taken a few 50+ milers with it. It is my daughters car and she does a little city driving with it mostly. It has been fine around town, never noticed anything unusual and the fuel pump was fine, but a couple of longer highway runs here lately and we noticed this issue. It concerned me that the gas mileage was no better on the highway, but the rpms seem a little high at cruise, like the automatic needs another gear. I guess I will need to do some searching, but wasn't all the turbos 3.54's, but the auto was an r180. I guess once again I have an issue that no one else had experienced-based on the lack of responses. Quote Link to comment Share on other sites More sharing options...
slown280z Posted July 29, 2009 Share Posted July 29, 2009 Have you changed the diff oil? It might be too old or too low. I don't think it's healthy for a diff to get red hot. Also, all turbos came with an 3.54 R200, and the final drive on the trans is 1:1, so yea, it does need another gear by today's standards, but the diff's speed is dependent on the car's, not the engine's. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 30, 2009 Author Share Posted July 30, 2009 My guess is that the oil is as original as the car. Time to order some synthetic I guess and rearrange my fuel lines a little further away from the diff. Also a good excuse to buy one of those laser temp guns. If it was my car, the 5speed would be in there, but it's my daughters car so it doesn't bother her, except when the Walbro is screaming and she asks me "is that normal":eek:, Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 30, 2009 Share Posted July 30, 2009 I would change the oil with normal diff. oil for a short time and then change to synthetic. Nothing like two quick oil changes to get rid of dirt. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 1, 2009 Share Posted August 1, 2009 drain the differential, refill it with the correct lube and carefully inspect it for leaks especially at the axle bearings and pinion areas, if the differentials run that hot its probably already damaged, try the new lube but ID start looking for a rebuild kit or new salvage yard rear differential Quote Link to comment Share on other sites More sharing options...
Yokohama Posted September 15, 2009 Share Posted September 15, 2009 Don't forget to inspect the magnetic drain plug for excessive metal shavings. Normally there will be a slight amount of buildup on the plug, but anything else may warrant closer inspection. Also look for things in the drained fluid. wipe the plug off before you put it back in and fill it up. Be sure to measure the correct amount of fluid and don't under or overfill. Quote Link to comment Share on other sites More sharing options...
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