Will 2" smaller in DIA tires cause automatic trans to shift at wrong RPM.

S,CLAY

MEMBER
1998 SUBARU OUTBACK
209,000 MILES

I just got this car at auction and it has some shifting issues. First thing I noticed is it has some 205 55 r16 and it came with a 205 70 r15. I changed the trans fluild and removed the pan for inspection and all looked good, but still has the shifting issue. I some times down shifts from 2nd to 1st when coasting down my driveway. Also when I take off it seems to rev high before going to third sometimes it goes from 2nd to 4th and then to 3rd.

4 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Roll speed is critical to all operations including trans.

As far as late shifting from tires, it will effect it a little but not a lot. You may have throttle valve issues in the valve body. Get it checked at a trans shop to verify.

Roy

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Sunday, May 13th, 2012 AT 6:18 PM

S,CLAY

MEMBER
5 POSTS

I don't trust any trans shop around here. So what can I do myself without removing the trans? Can I check the line pressure? Or replace the valve body or pressure regulator? I have no lights on the dash. Does that eliminate anything? What about reseting the ECM. Can that be done without going to the dealer?

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Sunday, May 13th, 2012 AT 10:44 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

You need pressure gauges, and the specs that need to be set. I will see if I can get them for you. If you never did this, I highly doubt you are going to be able to do this but we will try

Roy

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Monday, May 14th, 2012 AT 12:21 AM

S,CLAY

MEMBER
5 POSTS

Ok maybe your right. I think I can find someone I can trust to give me the diagnosis. But are there any parts that can be replaced by just removing the pan that might fix the problem?

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Monday, May 14th, 2012 AT 2:32 AM