My 91 240 has developed alot of play in the rear end. It started making a clicking noise while driving at low speed and especially on take off, and an occasional hum on the highway. I checked the u joints and drive shafts bearing they are fine but there is a lot of movement where the where the yoke goes into the rear end itself. Does anyone know what could cause this and how to fix it?

My '84 has made a humming at highway speeds since 300K. It now has 430K on it and while the noise has not gotten better, it has not gotten worse, either. This has been going on for 8-9 years at this point. The Dana 30's in our cars are pretty hearty units and given the relatively low horsepower and torque that our cars make (compared to other makes/models that the Dana 30 has been used in), they tend to wear very slowly.

The clicking sounds like a u-joint. The rear u-joint is a somewhat common failure. You might want to check your center carrier bearing as well.

Personally, if it were me, I would switch the rear end to a synthetic lube and not worry about until if/when it becomes a bigger problem. That could be years from now or never. I'd also check that rear u-joint and see if that isn't the issue.

Is your 1991 240 modded in anyway. Like some made a Turbo+ and dropped it in?

You say you have auto.

How many miles?

In the FAQ:

https://www.volvoclub.org.uk/faq/Driveline.html

Brickboard version (duplicate, really)
https://www.brickboard.com/FAQ/700-900/Driveline.htm

Play? Have you disconnected the rear drive shaft flange from the differential input flange? Do you mean the differential input flange moves around and around within the pinion seal. Or a back and forth or, maybe better, front to back, or to and fro, as you pull and push it, if you can.

Differential disassembly is daunting, yet not impossible.

Drain and inspect fluid. Any metal grit or metal pieces?

Dissemble the rear hubs including E-brake pads and assembly. Three bolts at each side, on at a time. With draw the half shaft. Support the half-shaft so it does not stress the inner or outer seals (factory should be a sea-green or light green blue color [Timken or SKF made these for factory, they still do for after market, and not too expensive, a bit of bother to replace]).

The retainer bits are accessed from teh rear and are left handed thread. Woops, here goes video

Changing the differential on my lifted volvo 945 turbo in time lapse:

https://youtu.be/_PVhHflmRaM

Howling 240 diff, yet sounds like clicks:

https://www.youtube.com/watch?v=BYSuXbJNcoQ

Clicking may be caused by a failed bearing either side or:

Info on LSDs, yet some general diff info in 240:

http://people.physics.anu.edu.au/~amh110/Diff_LSD/diff_lsd_volvo_dana.htm

Find the axle serial number on one of the axle tube at the rear facing side. If the serial number starts with an S, there is a compression sleeve. The sleeve resides behind the pinion bearing. I'm not sure.

If you need new parts, Dayne / Spicer can help. Though $$$

Swapping in a salvage pull as replacement is not hard, yet can take some hours.

Have you owned this for sometime? Or did you buy it recently? The prior owner may have abused it. Though the Dayna diff is hard, yet not impossible to damage. High miles, abuse, long fluid interchange, wrong fluid, or if a limit-slip diff it can be abused.

Some will weld an open diff 'closed' to drift (oversteer) which can damage the diff and axles.

Yours sound abused.

Hope that helps.
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fwiw. I had a Manual 75, that had Play and rumble noise in the rear that made itself apparent about a year after I bought it used at 75K.
I drove it until it rusted at impt points and burned a valve around 290K

Your big problem is that, as I gather, you have an automatic tranny. As such you cannot feather the clutch on take off to minimise the initial noises.

You are hoping to get thru the Winter? Just baby it as you take off from stopped.

"Your big problem is that, as I gather, you have an automatic tranny. As such you cannot feather the clutch on take off to minimise the initial noises."

I've always considered an auto box the ultimate clutch featherer if it is working properly.

My little experience is that diffs make noises like winning, werring, or waffling. I think clicking from a diff might come from something like a damaged tooth.

For the question on driveshaft movement, try shifting between drive and reverse with the engine running and brakes on and listen for clunks. If its quiet then its probably fine.

Also, if the clicking changes rapidly with speed, it might be something in the driveshaft since it rotates faster than the wheels.

You could put the axel on jack stands and try to reproduce the clicking. Have a second person to listen around the car.

If you really have excessive play in the rear (did you ever check it before the clicking for comparison?) I'm afraid the rear will need overhaul. The bad news is that's a job for the experienced (read costly). The good news is changing the entire rear axle assembly is fairly straight forward and should be plentiful. Others here on the BB may know which years are identical (as far as the signal for the speedo). Auto transmission and standard shift cars have different ratios---wagons and sedan ratios are the same.
Have you exhausted other possibilities - axle bearings, pebbles caught up in the brakes, etc. U-joints should be checked for tight spots by dis-connecting the joint and moving it through its full range. -- Dave

I have checked all the other issues you mentioned. I am a pretty experienced mechanic when it comes to Volvos, I have never had to do anything with a rear end. How hard is it to overhaul it? Changing the whole thing is not really an option since there are some rust issues with most of the bolts holding it in place, I would just like to get the poor thing through one more winter if possible and am willing to put a little work in if I can.

If you're looking for a band aid fix then the diff might just survive another winter if treated gently. I would certainly drain the oil and remove the cover, checking to see if there are any metal bits in the oil. They may be recognisable. With the axle on stands and the prop disconnected you may be able to spot the problem. How long it will last will depend on what you find and will also give you ideas on how easy it is to fix. Swapping a used diff probably easiest and could be the cheapest route depending on how lucky you are at the pick 'n pull. Any ratio for the later axle will do as a stop gap but with speedo errors and cruising ability to consider. If you're bouncing around in the snow this winter a low ratio won't be a problem. Sounds as if you know the score. Good luck.

What derek uk suggested regarding opening the cover to have a look -- and the possibility of running the car as-is was going to be my suggestion too if changing the works isn't an option.
I don't have a huge amount of experience with diffs but have worked on a few--a complete overhaul on one and adding a used lsd unit to another using new bearings and seals. It takes a special tool to stretch the housing in order to remove the "guts" - a press or bearing pullers to disassemble - measuring tools to set the gear depth/end play. Bearings alone could run a couple of hundred dollars - gears too?-lots more $--not a job to do just to get a few months use. -- Dave

That's what I thought would be the case but was hoping otherwise. Thanks for the input guys.