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Currently own 1984 dodge d150 and would like to know what the exact steps are for me to take in replacing the rear end. Due to continuous jumping and slamming when changing from "in park" to "reverse" or "in park" to "drive", there is a hard jolt/slam shortly after. Consulted a few friends and co-workers and they all seem to think that the rear end is on the Frits. Due to my current financial circumstances, I'm not going to drive it until it just breaks, which everyone suggests. Unless I want to pull apart the differential and I'm positive that won't go back together if that was the alternative due to the massive rust and lets just say it may fall apart if I touch it. Drivetrain is moving fine, so "U Joints" are not the issue. Really hoping I can get some feedback as to the issues I'm having. Please and thanks
 

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What motor, and what transmission? What gear set in the rear end, and do you care if that changes? Do you use the truck off-road, for towing, or do you care to
improve gas mileage or pulling ability? Do you have access to a good place to work on it?

I assume what you want to replace is the whole rear end from the post above -- see if you can find one in a boneyard or online to get an idea of the cost of parts.
The job is not difficult but it does take time. Depending on what tools you have and your working conditions figure at least a full day. Depending on what you find
what you get in there (bad brake lines, worn spring perches, etc.,) you may need to expand the project. If you've never worked on one, getting the parts via the
pick-and-pull route can be educational.

If all you want to replace is the differential, the job may be easier -- but this could still be a torque convertor issue, from the symptoms described.
 

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Welcome to Allpar. I would definitely confirm that the rear axle is the cause of the harsh engagement before just replacing it. Diagnose first. Many other things can cause the 'slack' in the drivetrain and rear suspension that you are experiencing.
With the wheels securely chocked and the vehicle on level ground, put it in neutral, crawl underneath and grasp the propeller shaft. Twist it CW and CCW to see if the slack is in the axle. Ring and Pinion backlash should be about an inch of freeplay on the prop shaft.
A factory service manual will help guide you with pictures and procedures on how things come apart and go together. It will also include a Possible Causes list that will give the suspects to rule out as you narrow down the list and focus in on the root cause. It will also show you how to measure play and what to expect for acceptable freeplay for the different components. The service manual could be considered a tool purchase and can easily pay for itself the first time you use it.
Some of the larger public libraries may also have good service manuals for loan. The Chrysler factory manual would give the best detail. Most car/truck RWD set-ups are similar and the same methods of diagnosis and service would apply pretty much to them all.
Safely watching for excessive driveline movement from the side or on a lift as you shift from D to R and back, may show where the play is. Loose or broken engine/transmission mounts, leaf spring shackle/frame mounts and delayed transmission internal clutch engagement are among the possibilities.
 

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The few people I have talked to seem positive that the problem is in fact the rear end. It is a RWD 318 5.2L btw..sounds like this will be more costly than imagined and I do not have anywhere to work that has correct tools though I may be able to find someone. Other technicians online say this would be bad to do by myself do I'm guessing I'll be looking more into this than planned. Not a very patient person but I'm getting there.thanks for all your concerns keep asking questions as I will do the same and will Definately check back in with what I find.

And no i don't dare if it changes, I'm not rrestoring the vehicle just trying to keep it going a little longer
 

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Have someone check the u-joints. If they're worn out, you'll have those symptoms.
 

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My biggest concern with swapping rear ends would be making sure the one you put in it is in better shape that what it replaces. Most of the replacements you get are also going to be around 30 years old as well.. The job itself is not that technical, more labor than anything.. tight old bolts that are often rusty.. and large heavy parts... Last few I've changed.. I just break the u-bold off; disconnect your parking brake cables, Hydraulic brake lines, and rear u-joint.. Not in that order. Do the U-Bolts last. And be sure you have your replacement first.. You'll want to make sure it is the same differential ( for speed and convenience) D44 for D44, 8.75 for 8.75, etc.. Verify they use the same U-joint.. I've done them in parking lots in a couple hours, and had them fight all the way through before..
 

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Well, if it is the rear end, the cheapest and simplest solution, in my opinion, is to pull another axle out of another truck at a self-service junkyard. If I remember correctly, 84 is THE LAST year of 5 on 4.5" for the half-ton trucks. You can probably pull an axle from any 5-lug half-ton truck from '72 to '84, and possibly even as far back as 1960. The trick will be to find the same gear ratio, so that it doesn't change how your speedometer reads. It might also be good to verify that the yoke is the same size. On the cars they used two different yokes, depending on if the car had the more powerful drivetrain or the less powerful drivetrain.

If you pull a used axle, probably a good idea to find a wrecked truck, rather than a truck in bodily-good shape, as the source. A wrecked truck was operating when it died, while a truck in good shape could be in the yard because the axle died.
 
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