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Cracker · 03-08-2007, 08:00 PM

Since numerous Airstreamers are running trucks with the Allison tranny I thought this might be of interest. Yesterday, with temperatures around 5 degrees, my Allison Tranny blew out about a quart of oil on my daughter's driveway - just after I started up and left the house for a couple of hours. If it wasn't for a "hesitant" start - where I took my wife back down the driveway (---change of plans) I never would have known exactly when it happened. When I returned and parked the truck I noticed the trail of transmission fluid and immediately started checking to see "wha hoppened" The boot on the shifting linkage - located on the left side of the tranny and roughly under the drivers floor pan - was soaked with tranny fluid. As for the fluid level, it was at least a quart low. It was too late to get to a service facility last night so I went first thing this morning. Since the facility I had to go to was foreign to me I checked with a knowlegeable buddy just to get a preliminary idea what to expect. Based on my description of what happened - and what I had observed - he immediately told me about a service bulletin addressing this very problem (---2003 and earlier.) It seems that when the tranny is exposed to extremely low temperatures over a period of several days it will, occasionally, blow oil out of the tranny vent when the vehicle is started up. He had personally experienced it with at least three vehicles that had lost over 2 qts each - and that had been towed in out of fear of damaging the tranny. There is a very expensive "fix" for the problem (---a "special" vent) --- but, in his opinion, the problem occurs so rarely that it just isn't worthwhile - especiallly since it stops leaking without any further action and before losing enough oil to damage the tranny. I went ahead and had my truck checked out - but they could find no sign of any other leakage (---ongoing or past) and they reported that the vent appeared to be dry. Back to my buddy with this information - he acknowleged that the vent tends to blow the fluid away as an isolated event (---sort of like a squirt gun) with no visible sign of fluid left immediately around the vent. Apparently it strikes something that causes it to saturate the boot on the shifting lever. The local garage added a quart of fluid and we drove 350 miles back to Maine. When we arrived home tonight the temperature had dropped to -5 degrees - so I'll check the transmission fluid level tommorrow! I damn near got frost-bitten fingers just getting unloaded!

While I'm on to truck peculiarities - I installed both winter shields on the grille for the first time. Previously I had only used the upper shield. This appeared to work nicely to keep the engine warm - however - the temperature readout on the rear view mirror read at least 25 degrees warmer than the outside air temperature for the entire trip home. This makes me wonder just where in heck the probe for this fancy mirror thermometer is located??? I'm now guessing that its located somewhere just behind the front bumper - although, up to now, I had always assumed that it was more in the vicinity of the rear view mirror on the outside of the windshield or roof. Can anybody solve this mystery?

dwightdi · 03-08-2007, 08:24 PM

There is a truck forum on the web somewhere but I did not keep the address in my favorites. You might get you better answers there. I have a 2001 8.1 with the allison. We are pretty cold around Chicago but I have never experienced this problem. I only have 40,000 miles on mine. Thanks for posting this problem, as I will know what to do if I ever happens to me. My thermometer works quite well. I have never installed the winter shields. Does it really help the engine warm up and stay warm better?