Big ol' Clunk in reverse
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
Big ol' Clunk in reverse
How much rearend movement is normal when you shift into reverse? Mine seems to move quite a bit and makes an awful racket. Seems to me after going to park or neutral I get more than a quarter turn of the driveshaft. Going back into reverse I can watch the shaft load up before the gears clunk. This is all with no movement of the tires. As far as I know the rearend could be dry, I haven't touched it yet. I assume that much racket means she's not as healthy as I'd like her to be. It's a 9 inch rear and I can't remember the gearing off the top of my head, 2.75 or 3.25 something in that range, I'd have to crawl back under and check, haven't seen the pictures of the tag in awhile.
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How much rearend movement is normal when you shift into reverse? Mine seems to move quite a bit and makes an awful racket. Seems to me after going to park or neutral I get more than a quarter turn of the driveshaft. Going back into reverse I can watch the shaft load up before the gears clunk. This is all with no movement of the tires. As far as I know the rearend could be dry, I haven't touched it yet. I assume that much racket means she's not as healthy as I'd like her to be. It's a 9 inch rear and I can't remember the gearing off the top of my head, 2.75 or 3.25 something in that range, I'd have to crawl back under and check, haven't seen the pictures of the tag in awhile.
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
I still haven't figured out what lube to put back in after I do, need to check the manual and try and translate that to modern, as I can't obviously drive it in good conscious knowing it's dry. I mean I can thinking it's dry, but that's different. No slop in the u-joints, so it's got to be in the rear gears, right?
Lead Driver
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I still haven't figured out what lube to put back in after I do, need to check the manual and try and translate that to modern, as I can't obviously drive it in good conscious knowing it's dry. I mean I can thinking it's dry, but that's different. No slop in the u-joints, so it's got to be in the rear gears, right?
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Mine has 400k miles on it. It's never been dry.
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
Looks like that way, I get about 3/8" travel measured on the perimeter of the... yoke? Doesn't seem as bad measured that way, but I can make it clunk by hand.
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Lead Driver
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
I feel like the 9" rear doesn't have a drain plug, but haven't looked closely at it in awhile. I figure I'll drain and flush and refill it when I get the chance, that way I'll know it's got good fluid in it. Now, that clunk, it's more of a slam.
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From: Virginia
If your idle speed is too high, it will aggravate the clunk noise. A little bit of play in these rearends is normal, these trucks are getting old and most were not babied all those years either.
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Cargo Master
Joined: Jan 2019
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From: Caraway, AR
How does the idle speed come into play, and what do you figure a good idle speed is? Got it set to around 750 right now. What worries me is how much everything moves without the wheels moving, when I put it in reverse. Doesn't move near as much going into drive.
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From: Virginia
When the idle speed is high, the torque converter transfers more of the engine power through the transmission. So when you put it in gear, you have to hold the brake down harder. More torque is being transmitted through the transmission, so it will turn a reasonable clunk into a bang in the rearend.
This is the main reason why I do not run full manifold vacuum on these trucks with automatic transmissions. It makes the idle speed too high when it's not in gear, and too low when it is in gear with a automatic.
This is the main reason why I do not run full manifold vacuum on these trucks with automatic transmissions. It makes the idle speed too high when it's not in gear, and too low when it is in gear with a automatic.
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To drain it you remove the cover. I have the 10.25, but yours is similar. Be sure to get a gasket before you change the gear oil. I used one of those permanent gaskets where you don't use sealer and it's reusable.
I'm in agreement with Franklin...adjust your idle as low as is practical. You don't want it stalling on you either.
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From: Virginia
No cover on the 9 inch. You more than likely have to suck it out. That is a lot of fun. That old gear oil is stinky stuff.
Once you get this thing going down the road, if the rearend is really noisy, I would plan on getting into it or swapping the whole thing out for a good one. If it's pretty quiet, I would live with a little play.
Once you get this thing going down the road, if the rearend is really noisy, I would plan on getting into it or swapping the whole thing out for a good one. If it's pretty quiet, I would live with a little play.