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Post by robic58 on Mar 23, 2011 14:11:11 GMT -5
-- I have a 302 cid Mercury with an AOD transmission. Car has 75K miles. Transmission has never had any service. Fluid is now salmon pink to tan color, and I want to chage it.although the transmission still works fine except for a harsh upshift from 3rd to overdrive.
Options: 1)replace all the fluid with new fluid
2)replace 50% of the fluid without dropping the pan
3)replace 50% of fluid,dropping pan,removing screen and reinstall with new gasket.
What would you do?
Thanks for replies, Ralph
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Post by jhkaster on Mar 24, 2011 4:33:14 GMT -5
My 82 XR-7 has a 255 (smaller version of the 302) with AOD. I was having hard shifts at times with the tranny. Turned out to be a problem with the carb. I'm not a carb guy, so I can only relate what my mechanic did. He replaced the power valve on the carb and adjusted the carb to factory specs. Ever since then, the shifts are smooth and almost undetectable.
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Post by chriscris on Mar 24, 2011 8:47:24 GMT -5
75k isnt a whole lot of miles, but personally I would go the pan drop route.
I would also check the vacuum modulator valve to see if it is leaking at all, and adjust the 'kick down rod' just to be safe
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Post by robic58 on Mar 24, 2011 15:46:20 GMT -5
James & Chris- Thanks for your input..I've decided to use the flush method to replace 90% + of the fluid... I just think my fluid got overly hot, due to defective rad which I've now replaced. I 'm also going to see about modulator replacement.
After all, I can't have everybody call me shiftless.
Thanks gents & Cheers, Ralph
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Post by gmcchamp99 on Mar 27, 2011 3:31:27 GMT -5
I'd be careful with tranny flushes on these older transmissions. The seals and bands tend to get "Set in their old ways" and become used to the thicker & more viscus transmission fluid. When you flush the tranny out, the good thing is your working out the sludge from over the years. The bad thing is the tranny is now depending on this sludge / fluid. Flush an older transmission that hasnt been cared for and you could be looking for a rebuild quite soon. Did that on the C-4 on my 1976 Ford Pickup and two days, 57 miles later i had no reverse and only first gear.
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Post by robic58 on Mar 27, 2011 17:06:20 GMT -5
Well, I've done it.. the term flush might be a little misleading.
The process used here by my local garage man, involves using the transmission's own pump and valves to purge out the existing fluid, all the while adding an equivalent amount of new fluid. My AOD tranny calls for 12.3 qts of mercon fluid. The flush or purge required 18 qts of fluid until a clear reddish pink discharge was achieved. I appreciate the concerns regarding seals,etc. but i feel confident about the process since my fluid two weeks ago was good and clean and a nice pink color with no odor.. the fluid literrally got cooked by overheating , bad radiator and hence no cooling to tranny fluid.. So far works fine, only 200 + miles since the big decision. I'll know soon o, I'm off in a week with a 3000 mile trip.
Thanks to everyone for their input. Really appreciate that. Cheers, Ralph
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