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Allison OEM Discuss repairing & maintaining an OEM Allison automatic transmission.

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Old 08-05-2019, 07:12 PM   #1 (permalink)
GORDONORTE
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+ 8.1 on a Sierra- shift rpms

Hi, I’ve just registered to the forum, hope to learn a lot from it now that I just acquired a GMC (I had Fords before). I’ve spend a few hours browsing through different forums trying to find any information on that, didn’t quite seem to find this specific info. I just bought an ‘03 Sierra with 171k and the 8.1/Ally5/3.73 pkg, I wasn’t looking specifically for this config. as I don’t tow/haul anything but it was a good deal.
Anyways, The deal is this: I’m quite used to my 91 Ford with the 460/E4OD where I can shift all the way to OD with rpms between 1300-1700, noticed that with the Ally I had to rev past 2000 to shift. 1-2 shifts about 1800 but the rest all above 2k. I don’t believe there is any problem, shifts are all smooth, so is this normal shifting rpms for the Ally? I would assume that such a high torque engine (not a diesel of course) could work in low rev when gentle on the throttle, but that was just my expectation... it might be just a matter of getting used to it or perhaps it needs a tune?

Have read a lot of good things about this engine and of course Allison is king, I was quite happy to know I got it as I thought they only were equipped in the Duramax.

Well, hope someone could clarify this rather simple question.

Cheers!
Art
Alberta, Canada

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Old 08-05-2019, 10:33 PM   #2 (permalink)
johnH123
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any vortec has to be revved. They are very rev-happy engines so its good to get up there. I usually shot for 4000 RPM or so when starting out in the 1-2 shift.

Looking at the torque curve for the 8.1, If i were you I'd shoot for 3000 RPM to get the max torque out there.

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Old 08-06-2019, 02:22 AM   #3 (permalink)
davester
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It's also possible the truck has already been tuned.
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Old 08-06-2019, 11:49 AM   #4 (permalink)
GORDONORTE
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Interesting, I did notice the 460 delivery its torque at rpms lower than the 8.1, but I thought this would only make a difference when under load... well, i have no experience with towing though...
This truck's bed is intact so most likely it spent its whole life towing, I will check with the previous owner if the TCM was tuned.
Cheers,
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