Allison Transmision not shifting

I have a 2003 2500HD diesel with the Allison trans. I changed the filters and fluid at 30000 miles. I tow occasionly and plow snow. I now have 67000 miles and the trans stopped shifting. I only have 3 speeds out of 5, engine light is on, Shift indicator shows 3 when in drive. Anyone have any ideas?

Reply to
Louis Cyktor
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tre trans is runing if fail safe mode its still under warant take it to gm dealer more than likely it is the range switch

Reply to
jshammer

Reply to
Louis Cyktor

Reply to
Louis Cyktor

Reply to
Louis Cyktor

It's going to be interesting to see what comes of another 2500HD I know of w/ the Allison in it that just exhibited a similar issue. The shift indicator would indicate a different gear than the truck was really in AND when it did go into gear, it would slam into the gear. It suddenly cleared up later that day and has been fine for three days, but it is going into the shop tomorrow. It is under the extended warranty as well. Sure sounds like everything I've seen about the NBSU switch everywhere on the web. It's yet another known issue . . .

Oh yeah, I've seen it reported that the NEW version of the switch, a black plastic, runs around $50 from an Allison shop and can be replaced easy enough by the DIYer. I understand the BAD version of the switch is tan in color. Wonder what version they replaced yours with??? Seems to me, it would definitely be worth crawling under it to look.

Reply to
Kevin

Aftermarket extended warrantees are worded very carefully as to what they will and will not cover. Mostly so they can not cover items. The GM Extended warentees are better, as they are very clear about items not covered.

Call the warantee company and ask to speak to a customer services rep. Charles

Reply to
Charles Bendig

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