| Transmission Noise - Higher RPM "Thump" when Shifting Up. [message #251920] |
Tue, 10 June 2014 22:55  |
Clark76
Messages: 62
Registered: February 2010
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Should I be concerned about my hard shifting "Thump" and what actions should I take to fix it?
After an event free smooth shifting 1,600 mile journey two months ago, I started my coach for the first time today since trip. My routine, Start, Idle in Park about 3-5 minutes to allow airbags to pump up then back out of the Storage Shed. This time I noticed a new fresh small 5" diameter puddle of transmission fluid on the concrete where the overflow line from the transmission sits. None has been there before.
(I have since learned that after sitting for lengthy time, it is best to engage the transmission into drive, with foot on brake, to allow transmission to circulate better through the system while the engine warms up vs. just keeping it in park which tends to "Burp" out transmission fluid as mine did.- true?)
I drove 6 miles on the streets and noticed a little higher RPM noise(no gauge) before the transmission would shift from 1st to 2nd gear at around 25-28 mph on flat surface. The shift was HARD - a noticeable "Thump". This happened after each stop/go on my six mile journey. This is a new sound/feel while driving. At the end of the 6 miles, the Trans Temp was 150 degrees. A check of the fluid level indicated it was about 1/8" to 1/4" below the lower mark on the Transmission dip stick. About ~12 OZ of Transmission fluid was added to bring the level up to mid-to high mark.
Now, After 1 hour of smooth driving at highway speeds and 180 degree Trans Temp, Trans fluid level still shows full on the dip tube (assume it is calibrated correctly). Yet, after the hour drive and now driving on local streets in stop/go traffic, the higher RPM/HARD shift is still noticeable from 1st to 2nd and 2nd to Third.
Additional background: The transmission was rebuilt 2 years ago by a GMC tranny guru. To my knowledge the transmission has not been above ~200 degrees and less than about ~8,000 miles on the new re-build. The fluid is clean and pink using Mobil 1 synthetic transmission fluid.
Should I be concerned about my hard shifting "Thump" and what actions should I take to fix it or diagnose it better and keep it from doing this again?"
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