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Old 07-26-2000, 07:17 AM   #1
Scooby Newbie
Member#: 1962
Join Date: Jul 2000
Question 91 Legacy Transmission lag - help

My 91 Legacy L FWD hesitates when up shifting and it allows the engine to race between shifts, so that when it does shift, the transmission engages abruptly into the higher gear. With 105,000 miles, does this appear to be a transmission problem or a problem related to the detonation sensor connected to the cpu? If the latter, has anyone tried the aftermarket fixs of modifications to the cpu box sold on the net?
Thanks for your advice.
Tom Simiele
Cleveland, Ohio
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Old 07-26-2000, 08:26 AM   #2
Scooby Newbie
Member#: 1919
Join Date: Jul 2000
Location: Markham, Ontario, Canada
1994 Legacy Turbo


Have you checked your transmission fluid lately? Also, I'm curious as to what lead you to believe that it might be related to the detonation sensor? It's not obvious to me as to how it would be related to the transmission. In other words, this sounds like a transmission problem to me.

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Old 07-26-2000, 08:43 AM   #3
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Member#: 1962
Join Date: Jul 2000

The transmission fluid is full and no unusual oders. I read on the following internet site http://home.earthlink.net/~hobiegary/hesitation.htm that the sensor causes the engine to run erraticaly and thus may cause the transmission to act inappropriatly. I have not heard of transmission failures of Subarus before and this was the only information I could find on the subject. My next step is to go to a local dealer for their opinion, but I wanted to gain some knowledge of possible causes before I got to the dealer. Obviously we don't want to invest too much money in a 91 car with over 100,000 miles on it. In all other respects, it is a good vehicle. Its our second Subaru and we love them.
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Old 07-26-2000, 09:05 AM   #4
Scooby Specialist
Member#: 1353
Join Date: Apr 2000
2001 Impreza 2.5RS


I've seen in an SVX FAQ section about how to adjust the brake band in the transmission. Apparently if it's too loose, it will cause that type of problem. I don't know how different the Legacy trans may be, but I think all automatics have brake bands, don't they? Somebody may know better than me. I'll find the link and post it here so you can read it.


Here's the link, but apparently it's down right now. Sorry.

[This message has been edited by richeich (edited July 26, 2000).]
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Old 01-21-2017, 11:58 PM   #5
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Member#: 461711
Join Date: Jan 2017
Location: Ohio
1991 Legacy

Default 91 Legacy AT - acceleration lag AFTER 2-3 upshift

Hello All,

New to these forums and looking for some 4eat advice that appears related to this thread. I have a recently acquired a 1991 Subaru Legacy wagon with the automatic transmission (142,000 miles). After a week of local daily driving, I've noticed a couple things regarding the transmission. Most interested in thoughts on #2.

1) This week the 16-flashing POWER light deal on the dash happened. Went through the process to determine code...TCU code 22 - Atmospheric sensor. Unfortunately, not a solenoid that can be replaced from what I gather, but actually has to do with the ECU. Checked the OBDI engine codes, no corresponding ECU atmospheric sensor fault (would be code 45). After a full reset of the ECU/TCU (pulling fuse 14 from the driver side kick panel) this has gone away (for now).

2) However, despite the TCU POWER indicator not coming on after the reset, I am still experiencing my primary cause for concern. From a stop, upshift from 1-2 has a little "thud" (not too unusual for the 4EAT from what I gather). Then upshift from 2-3 is smooth, BUT, there is an acceleration lag AFTER the shift before the car starts forward again (I have NOT let off the accelerator pedal at all). It doesn't last long, but it's obvious and annoying. It seems to become less pronounced the longer I drive the car.

3) Fluid looks brand new, reddish and clear, not burnt or brown looking at all. It is however above the high mark on the HOT side after driving the car and go through all the gears while on a level surface.

Any thoughts on these issues, particularly #2? My plan is to drop the transmission pan, replace the filter, add new fluid, as well as replace the inline transmission filter located near the coolant reservoir. Could it be something to do with the brake band and if so, go tighter or looser? Is there cause for concern here?

Thanks in advance for your time and thoughts.

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