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4EAT slow shift 2-3
Posted: Mon Nov 04, 2013 12:51 am
by 93Leg-c
On my '94 TW w/4EAT, the shift from 2nd to 3rd is slow. It's especially disconcerting when merging onto a freeway only to find that the car won't want to increase in acceleration as it's shifting. I end up losing several car lengths until the tranny locks into 3rd gear.
In reviewing the FSM per
http://www.main.experiencetherave.com/s ... andadj.jpg, it seems that symptom #3 in the chart fits my situation. I followed the procedure of tightening down the adjusting screw then backing it out 3 full turns. (Before adjusting it, the screw was turned out 2-1/2 turns.) The tranny still does the same thing.
So, is there anything else I can do? Is the tranny on its way out?
Any thoughts would be appreciated. Thanks!
Re: 4EAT slow shift 2-3
Posted: Tue Nov 05, 2013 3:20 am
by Legacy777
The band is probably worn, so what you can try and do is adjusting that nut slightly a little tighter to compensate for the worn band. If the screw was adjusted 2-1/2 turns originally I would try adjusting it to 2 turns.
If it is too tight it just won't shift from 2 to 3, and will stay in 2nd.
Re: 4EAT slow shift 2-3
Posted: Wed Nov 06, 2013 5:55 am
by alexandermf
Mine does the same thing but worse when its cold, once it warms up if shifts a lil faster/quicker
Re: 4EAT slow shift 2-3
Posted: Wed Nov 06, 2013 6:21 am
by 93Leg-c
Thanks for the reply and suggestion, Josh. But I have a question: As the band wears, does the clearance increase or decrease? I ask because the FSM says the symptoms I'm having is because the clearance is small. If the bands wear, wouldn't the clearance increase thereby causing symptoms 1 or 2 (wide or too wide clearances)?
Also, because the position of the bands have changed with the adjustment, does the ecu have to "re-learn" the new settings for proper shifting? I ask this question because sometimes the 2-3 shifts are improved and at other times they are the same as before (noticeable lag upshifting into 3rd) and I was thinking that perhaps the ecu's control of the tranny was being affected and that it would take some time before it knew what the new band settings are.
Re: 4EAT slow shift 2-3
Posted: Thu Nov 07, 2013 6:36 pm
by Legacy777
From what I was told by the guy who rebuilt my valve body many years ago, the band is around a drum, and as the friction material wears the clearance will increase. By adjusting the nut just a little tighter then spec you help bring the band & drum clearance closer to spec.
As for the TCU, no I don't think it's learning anything. I think the variations you are experiencing is due to other inputs like TPS, vehicle speed, line pressure, etc. I remember similar experiences with my auto. Sometimes it would shift great, other times it sucked.
Re: 4EAT slow shift 2-3
Posted: Thu Nov 07, 2013 6:54 pm
by 93Leg-c
Thank you, again, Josh! That explanation was helpful and reassuring.
Re: 4EAT slow shift 2-3
Posted: Thu Nov 07, 2013 6:58 pm
by Legacy777
You're welcome.
All you can do is give it a shot. It may help or it may not. It won't cause any permenant damage, it just may not shift from 2nd to 3rd. In which case you just need to back off that adjustment nut.
Re: 4EAT slow shift 2-3
Posted: Thu Nov 07, 2013 11:01 pm
by 93Leg-c
Oh, that's good to know that it won't cause permanent damage. That's even more reassuring. I was concerned about that. Thanks, Josh!