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Old 10-25-2020, 03:52 PM   #1
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Overdrive issue

Hey guys, I've got an Allison 1000 in an 01 Workhorse chassis behind an 8.1 that we picked up less than 6 months ago. '02 Thor Windsport. First time really up to speed on the highway yesterday, and It's not shifting into 5th. Also the OD lockout on the dash does nothing, it doesn't even light up. Could those two issues be related?

Fluid level is good, temps ran cool, less than 170. I replaced a leaky cooler and added a temp gauge a couple of weeks ago. Replaced 8qts. at the time with tes 295. Have not replaced the spin on filter yet. It doesn't feel like there are any other issues, ran great for 100 mile round trip shakedown cruise on the highway. Shifts quick smooth and crisp. Can clearly see shifts on the tach but doesn't feel harsh or anything. Can feel (and see) it shift up through 4th, (and torque converter lock in second) but no fifth. RPM about 3000 at 65ish. I feel like I should be more like 2200 to 2500 @ 65ish? (I have the same motor/trans in an 01 Sierra 2500) No check whatever lights on the dash either.

Any ideas what to start looking for?
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Old 10-27-2020, 06:23 PM   #2
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Update, the 2 issues are related. It appears that at some point the wrong OD lockout switch was installed. Apparently the momentary switch that was installed happens to have NC contacts where the wires from the TCM land, therefore keeping it locked out all the time.

I unplugged the switch and went for a drive and it shifted to 5th like it should at 55. I just wonder if it left the factory that way and has never been in 5th gear until tonight.
2002 Four Winds Windsport 33SL, W20, 8.1/Allison
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