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Astro/Safari Towing

4 messages,  Last post on Dec 07, 2009 at 12:15 PM

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#1 of 4 Towing button activated makes a thud sound when shifting by nichu Mar 08, 2008 (7:40 pm)
Does anyone know what would cause this issue: When I press my towing mode button on my shifter knob, when the car shifts from 1st to 2nd, it makes a loud thud sound. Again I dont know exactly which gear it is shifting in. But it only makes this sound when the tow button is enabled. With the tow mode off, the car shifts just fine?   Any help? Replies to this message: 1998lincoln (Nov 17, 2009 3:51 pm) spike99 (Dec 06, 2009 7:53 am) spike99 (Dec 07, 2009 12:15 pm)
#2 of 4 Re: Towing button activated makes a thud sound when shifting [nichu] by 1998lincoln Nov 17, 2009 (3:51 pm)
Replying to: nichu (Mar 08, 2008 7:40 pm) WWWHHHHAAATTTT ?
#3 of 4 Re: Towing button activated makes a thud sound when shifting [nichu] by spike99 Dec 06, 2009 (7:53 am)
Replying to: nichu (Mar 08, 2008 7:40 pm) .   Perhaps its a wording thing in the initilal post. Unknown to some. this "Tow/Haul" button should only be pressed (in or taken out) before vehicle is taken out of "P" gear. It should NOT be pressed in/out when driving down the road.    ----------    The tow/haul button forces the vehicle's transmission to rev higher before shifting into its next available grear. Many say this feature "raises its shift points". If wondering, having a higher reving engine before shifting is a good thing (especially when vehicle is under load stress). Higher engine revs means less stress on the transmission. And, less "stress heat" being created by the transmission. Low RPM shift points create huge amount of internal heat. Thus, why many "tow capable" GM vehicles have tow/haul button feature as their minimum build.   If one's transmission becomes "worn out" (re: high mileage or too much load stress during its many years), the transmission's "shifting" mechanism becomes loose (re: out of factory specs). Thus, rougher feeling when shifting up each gear. And when using the Tow/Haul feature, the engine is reving higher then normal shift points. Unfortunately, higher reving "shifting" transmissions don't like worn out gears.. Thus, why your vehicle shifts ok in normal mode but makes ugly "weird" sounds when in Tow/Haul mode.   Long post short.... The vehicle's transmission needs a re-build. Thus, replacing worn out inner parts with new parts. And, these new parts are better then factory GM specs. As a "short term" solution, I'd replace transmission ATF, its under pan filter and install new Dexron ATF. Add some Lucas Transmission fix additive as well. re: http://lucasoil.hodgsoncorp.com/slipping_transmission.htm This "liquid fix" might resolve some "weird" transmission sounds and behavior. Especially if you plan to sell your van (and try to get top dollar for it). But for long term resolution (if you plan to keep your van for many more years), get your van's transmission re-built. Many specialized transmission shops will provide a rebuild estimate (using standard rebuild kits). Do shop around because rebuild prices do vary. If wondering, my previous van's transmission was rebuilt for $1,100. Afterwards, it ran better then factory. Glad I got its transmission rebuilt.   Also... Do install an Aux LPD Transmission cooler on your van as well. Go with LPD design for towing $5,000+ lbs trailers. The 460LE transmissions do NOT like heat (even only used for soccer parent driving conditions). If you don't already have one, do install a HD Aux cooler. For example: http://www.transmissioncoolers.us/Merchant2/merchant.mvc?Screen=PROD&Product_Cod- - - e=1679&Category_Code=hayden-transaver-cooler&Product_Count=3 Note: My local transmission specialist recommends "over sized" LPD coolers for all GM vehicles. Especially for the 460LE transmisison (found in Astro/Safari vans) - that cannot handle high amounts of "stress heat" & reginal weather heat.   Hope this helps...   .
#4 of 4 Re: Towing button activated makes a thud sound when shifting [nichu] by spike99 Dec 07, 2009 (12:15 pm)
Replying to: nichu (Mar 08, 2008 7:40 pm) Just want to emphasis....   If your van tows / hauls 3,000+ lbs and/or you live in hot summer climate, I'd install the # LPD4590 tranny cooler. Its next size larger (then my prevous post) and can take "the heat" much better then its slightly smaller size cooler. For more details, surf:   http://www.transmissioncoolers.us/Merchant2/merchant.mvc?Screen=PROD&Product_Cod- e=4590&Category_Code=trucool-coolers-hd&Product_Count=2   Hope this helps as well...   .

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