Author Topic: th350 transmission sucking air?  (Read 1015 times)

Offline jg1977c20

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th350 transmission sucking air?
« on: April 30, 2015, 07:50:32 PM »
hello is it possible for a th350 to pull air in thru a loose speedo cable ?  just curious if the speedometer cable nut was loose at the trans would it allow air to be sucked in ? seems logical but cant find a an anwser to this question anywhere , also when i tighten the cable hand tight to the bullet it pushes the speedo (driven gear ) further out the bullet and causes the speedometer to bounce if i loosen it a bit it works normal ?
« Last Edit: April 30, 2015, 08:03:42 PM by bd »
1977 c20 cheyenne camper special 8200gvw

Offline bd

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Re: th350 transmission sucking air?
« Reply #1 on: May 01, 2015, 07:58:11 PM »
hello is it possible for a th350 to pull air in thru a loose speedo cable ?

Elaborate.  What prompted this question?  Is there a problem you're trying to solve?

when i tighten the cable hand tight to the bullet it pushes the speedo (driven gear ) further out the bullet and causes the speedometer to bounce if i loosen it a bit it works normal ?

Remove the speedometer driven gear support bushing (the part that you are calling a bullet) along with the driven gear from the transmission case.  Reconnect the speedo cable to the bushing/gear assembly while it's out of the transmission and check the depth of penetration of the cable into the gear - does the cable bottom out and bind the gear.  Use a flashlight and inspect the teeth of the drive gear on the tailshaft and the driven gear for wear.  Inspect the shaft of the driven gear for concentric wear grooves.  Inspect the gear hole through the support bushing for eccentric wear (is the hole worn oval?).  Reinsert the driven gear and wiggle it from side-to-side in the bushing - there should be no more than about 0.003" of side play.  Replace any parts that are worn and reassemble with new seals.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline jg1977c20

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Re: th350 transmission sucking air?
« Reply #2 on: May 04, 2015, 05:44:08 PM »
BD    thanks for the info -yes the cable actually wouldnt go far enough into the driven gear - i suspect age (origonal cable ) made the wires unspring  if that makes sense making the inner cable diameter slightly to big - i also finally found the wear on the gear stem so replaced the gear and cable - no leaky no more  :)
1977 c20 cheyenne camper special 8200gvw