NA8C Auto trans problem

broomfish · Post by **broomfish** » Fri Jun 27, 2008 8:42 pm

We have an auto NA8C which performs fine except for the overdrive.

When we drive it from cold it takes much longer than it should before it drops into top gear. From my experience on other models, the trans is stopped from enaging top gear until the engine is at operating temp to minimise load on the engine.

Can anyone help with info as to which sensor might be faulty, or if i might be looking the wrong way?

thanks
Peter

Growler · Post by **Growler** » Sat Jun 28, 2008 9:57 am

Just a thought - when was the last time you changed the transmission fluid?

broomfish · Post by **broomfish** » Sat Jun 28, 2008 2:23 pm

Growler wrote:Just a thought - when was the last time you changed the transmission fluid?

I have just replaced the fluid and internal filter. the problem was like that before hand. The shifting is perfect except for the lazy overdrive. Once it is warm it shifts into overdrive perfectly, so i suspect the sensor telling it that it is warm is faulty.

broomfish · Post by **broomfish** » Sat Jun 28, 2008 2:24 pm

Growler wrote:Just a thought - when was the last time you changed the transmission fluid?

I have just replaced the fluid and internal filter. the problem was like that before hand. The shifting is perfect except for the lazy overdrive. Once it is warm it shifts into overdrive perfectly, so i suspect the sensor telling it that it is warm is faulty.

Ian · Post by **Ian** » Sat Jun 28, 2008 3:41 pm

My w/shop manual suggests when there are any probs with the auto trans, as a first step, check the electrical connections between the underside of the trans tunnel and the top of the transmission ie that the connection is sound and clean. I would imagine it is a fairly dirty environment........

Stevo · Post by **Stevo** » Sat Jun 28, 2008 7:25 pm

try replacing the thermostat. When it jams open, it takes a long time for the water temp to rise to normal. Cheers Stevo

broomfish · Post by **broomfish** » Fri Feb 19, 2010 4:24 pm

Stevo wrote:try replacing the thermostat. When it jams open, it takes a long time for the water temp to rise to normal. Cheers Stevo

Just revisited this post and thought i would update what the cause was. The thermostat was working ok, but had something (never did figure out what it was, looked like a roller from a roller bearing!) jammed in it causing it to stay open thus causing a longer warm up period. Replaced the thermostat and problem solved.

Stevo · Post by **Stevo** » Fri Feb 19, 2010 8:53 pm

Great result. Some thermos have a small (normally plastic) ball attached over a bypass hole drilled in the housing. This may have come adrift? Cheers Stevo

NA8C Auto trans problem

NA8C Auto trans problem

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