Hi, wondering what kind of job it is to replace an axle boot.
I have a 1986 944 turbo that has a leaky axle boot. I bought the replacement part that came with the pouch of grease to put in there. What was dripping out seemed like it was thinner that what is in that pouch thing...
Curious if this is a rather big job or pretty quick job?
rear axle boot replacement
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ROB III
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I would say big. It will be easier if you take the axle off the car, and best if you take the rear wheels off for better access to bolts. You will need to take the CV joint off the shaft so you will need triple square bit to get the bolts out of the hub/transaxle flange, snap ring pliers for the CV retainer clip, and I'd suggest gloves as its a pretty messy job. Since its been leaky, you might want to clean the CV, then pack in fresh grease in the CV before you slip on the new boot, then the reconditioned (or new) CV, install the C clip then tighten the bolts with the triple square bit.
When you reinstall the axles, make sure the threads for the bolts are CLEAN of grease as in my research, on RL, a lot of people seemed to have the bolts backing out even when torqued to proper spec. I used all new bolts as well to make sure I didn't have that issue. I also used a Q-tip to clean all the threads in the hub/flange before inserting the bolts. Once installed and torqued to spec, I drove several miles and checked the bolts again to make sure all were still at proper torque spec.
Here are a couple videos I watched before replacing the grease on all four of the CV joints.
The first is a video you'll need to click on to view it, the other two are from Pelican Parts for a 914 but gives you an overall idea.
https://www.bing.com/videos/riverview/r ... ORM=VRDGAR
Rebuild CV joints part 1
Rebuild CV joints part 2
When you reinstall the axles, make sure the threads for the bolts are CLEAN of grease as in my research, on RL, a lot of people seemed to have the bolts backing out even when torqued to proper spec. I used all new bolts as well to make sure I didn't have that issue. I also used a Q-tip to clean all the threads in the hub/flange before inserting the bolts. Once installed and torqued to spec, I drove several miles and checked the bolts again to make sure all were still at proper torque spec.
Here are a couple videos I watched before replacing the grease on all four of the CV joints.
The first is a video you'll need to click on to view it, the other two are from Pelican Parts for a 914 but gives you an overall idea.
https://www.bing.com/videos/riverview/r ... ORM=VRDGAR
Rebuild CV joints part 1
Rebuild CV joints part 2
Rob
89 944 Turbo
Musik-Stadt Region
89 944 Turbo
Musik-Stadt Region
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Tom
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What Rob said. 
It's a messy job, but very doable on jack stands. I would absolutely take the axles out and do it on a bench. Trying to change the boot under the car with one side of the axles still attached sounds like a nightmare -- one of those things were saving 5 minutes ends up taking an extra 3 hours... Personally, since you have to take it all apart to get the new boots on, I would just go ahead and replace the CV joints while you are at it. Or, if your laziness to cost ratio is as out of whack as mine, just get new axles with freshly packed grease ready to bolt in. As Rob said, make sure the bolts and holes are clean and torque the bolts in stages in a star pattern. I mark them with a torque pen to make sure they aren't backing out. If they don't start backing out in the first 100 miles, they probably never will.
It's a messy job, but very doable on jack stands. I would absolutely take the axles out and do it on a bench. Trying to change the boot under the car with one side of the axles still attached sounds like a nightmare -- one of those things were saving 5 minutes ends up taking an extra 3 hours... Personally, since you have to take it all apart to get the new boots on, I would just go ahead and replace the CV joints while you are at it. Or, if your laziness to cost ratio is as out of whack as mine, just get new axles with freshly packed grease ready to bolt in. As Rob said, make sure the bolts and holes are clean and torque the bolts in stages in a star pattern. I mark them with a torque pen to make sure they aren't backing out. If they don't start backing out in the first 100 miles, they probably never will. Much thanks both of you! I bought just the boot and it came with a clamp and the grease. I'll definitely be pulling the axle out and cleaning/regreasing the cv joint in there.
Should I be concerned with how thin the oil/grease is that is leaking out?
Should I be concerned with how thin the oil/grease is that is leaking out?
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ROB III
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Thin grease would lead me to carefully inspect the CV joint itself for unusual wear pattern or discoloration due to high heat. Its also possible that water intrusion has diluted the grease, but since water and grease aren't normally friends, heat may be the driver there.notny41 wrote: Wed May 28, 2025 11:29 am Much thanks both of you! I bought just the boot and it came with a clamp and the grease. I'll definitely be pulling the axle out and cleaning/regreasing the cv joint in there.
Should I be concerned with how thin the oil/grease is that is leaking out?
As Tom stated, it can be done on jack stands, which is how I did mine. He made a great point of marking the bolts with a pen to check for maintaining final torque setting.
I had to replace one CV joint but just repacked the others (my car had about 50K miles when I did this). If you replace a CV joint, pay attention to the info of the first attachment I sent for indexing of CV joint outer cages as well as one end of the axle to the other. I also used some paint to index the shaft to the hub and diff flange to try to maintain their original relationship (probably overkill on my part). Another thing I found useful when aligning the bolt holes on the hub end, I marked (fluorescent paint dot with a Q-tip) each hole above the hole because when you try to mate the boot hole to the hub, the holes were obscured by the mating surfaces.
Rob
89 944 Turbo
Musik-Stadt Region
89 944 Turbo
Musik-Stadt Region
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dr bob
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In my limited experience...
All four CV joints and boots have probably covered the same number of miles. I -never- replace just one, just so I can do all of them and have just one slimy mess to deal with.
The CV joints themselves are ambi-directional, so it makes sense to carefully inspect the wear faces in the grooves, and maybe plan on swapping the left and right axles so you can add wear to the less-worn faces.
It's important to keep careful track of the pieces and their installed positions. I punch match-marks in pieces so there's no question about how they will go back together. The inner parts of the CV joints must go back on the same way they came off.
If there's any bluing or pitting on any CV parts, just replace the joints. I used to hunt down 930 CV joints for my way-way-back-when weekend race car. There are different spline counts on the joints where the axles fits, so shop carefully if you go this route.
Porsche used to recommend replacing the axle nuts. I don't know if that applies to the 944, but it's generally a Good Idea.
If your 944 axle nut has a similar tightening torque to the ones on the 928, you'll want to remove them with the tires on the ground and probably have an assistant with a foot on the pedal. I have a handy 3/4-drive accessory that originally used a small cross-bar. The bar is removed, and I use a 6' demolition bar (from Home Depot...) through the hole to improve my mechanical advantage when loosening the nuts. With a little bit of math, a tape measure and your bathroom scale, you can figure out where to put a shoe to get sufficient tightening torque. I added a capable 3/4-drive torque wrench to the tool collection for this and the crank nose bolts, and it hangs for years between uses. But for the axle nuts, the careful application of body weight on the bar is more than sufficient. Places that install truck tires will do this tightening for you for not a lot of dollars if there's any question..
The Most Challenging Part of this project is the grease and the cleaning tasks. I prepare a small bucket of deodorized mineral spirits. Wipe all the grease out that you can with paper towels while wearing a sacrificial apron, heavy rubber gloves, and probably a face shield but goggles will do. Then into the paint thinner and attack with a stiff-bristle parts-cleaning brush. They need to be pretty much lickin' clean so you can do a detailed inspection. Again, any pitting or discoloration is good reason to replace the whole joint.
The boots go on with metal strap clamps that need a pinching tool to tighten correctly. Resist the urge to just use wire cutters, as they don't correctly add the stiffening dimple in the back to keep the clamp closed. This is another tool that will languish for years between uses, but is really the only good option. Works for steering rack boot clamps too. You may be able to free-rent this tool and maybe the big torque wrench at a better local parts store.
On my 928, there's a paper gasket and a metal 'cup' cover that fits over the end of the inner CV joint and axle. Replace the gasket if yours has one. I tie the cap on the end with some fine wire or even plastic cable ties through a few holes.
As others have recommended, the bolt threads and the threads in the drive flanges need to be really really clean before assembly. This is one of only a few cases where I recommend Brake Clean for cleaning parts. Use care, because the higher-boiling solvents used in that stuff is 'fat soluble', and causes nerve and eventually brain damage. Skin contact, breathing, and especially eye exposure to vapors pose a serious health hazard.
Anyway, bolts go into the clean and flushed holes without the ties and get a few turns to support the joint. Cut and pull the ties, and the rest of the bolts go in. Tighten them progressively and evenly until snug, then do the final tightening with a helper with a foot on the brake. I assemble a few long extensions so I can sit outside the wheel and reach the tools through to get each bolt. That way I can rotate the disk from bolt to bolt, helper applies the brakes, and you get to torque the bolts in an alternating pattern as you might with wheel lug nuts. Once tight, I use a paint pen to make index marks on every bolt to the flanges so I can easily see later if they've moved.
------
The Good News is that this project happens here only a couple times in the life of most cars. I did mine at about a dozen years old, and the car is now closer to three dozen years old. They get at least an annual inspection, and I do watch for the telltale black grease-sling stripe on the surrounding surfaces. On my car anyway, the rear crossmember and the rear wheelhouse liner are the willing receptors of CV joint grease when a boot cracks. That grease is more than a casual chore to remove from the otherwise-pristine undercarriage and liner areas.
All four CV joints and boots have probably covered the same number of miles. I -never- replace just one, just so I can do all of them and have just one slimy mess to deal with.
The CV joints themselves are ambi-directional, so it makes sense to carefully inspect the wear faces in the grooves, and maybe plan on swapping the left and right axles so you can add wear to the less-worn faces.
It's important to keep careful track of the pieces and their installed positions. I punch match-marks in pieces so there's no question about how they will go back together. The inner parts of the CV joints must go back on the same way they came off.
If there's any bluing or pitting on any CV parts, just replace the joints. I used to hunt down 930 CV joints for my way-way-back-when weekend race car. There are different spline counts on the joints where the axles fits, so shop carefully if you go this route.
Porsche used to recommend replacing the axle nuts. I don't know if that applies to the 944, but it's generally a Good Idea.
If your 944 axle nut has a similar tightening torque to the ones on the 928, you'll want to remove them with the tires on the ground and probably have an assistant with a foot on the pedal. I have a handy 3/4-drive accessory that originally used a small cross-bar. The bar is removed, and I use a 6' demolition bar (from Home Depot...) through the hole to improve my mechanical advantage when loosening the nuts. With a little bit of math, a tape measure and your bathroom scale, you can figure out where to put a shoe to get sufficient tightening torque. I added a capable 3/4-drive torque wrench to the tool collection for this and the crank nose bolts, and it hangs for years between uses. But for the axle nuts, the careful application of body weight on the bar is more than sufficient. Places that install truck tires will do this tightening for you for not a lot of dollars if there's any question..
The Most Challenging Part of this project is the grease and the cleaning tasks. I prepare a small bucket of deodorized mineral spirits. Wipe all the grease out that you can with paper towels while wearing a sacrificial apron, heavy rubber gloves, and probably a face shield but goggles will do. Then into the paint thinner and attack with a stiff-bristle parts-cleaning brush. They need to be pretty much lickin' clean so you can do a detailed inspection. Again, any pitting or discoloration is good reason to replace the whole joint.
The boots go on with metal strap clamps that need a pinching tool to tighten correctly. Resist the urge to just use wire cutters, as they don't correctly add the stiffening dimple in the back to keep the clamp closed. This is another tool that will languish for years between uses, but is really the only good option. Works for steering rack boot clamps too. You may be able to free-rent this tool and maybe the big torque wrench at a better local parts store.
On my 928, there's a paper gasket and a metal 'cup' cover that fits over the end of the inner CV joint and axle. Replace the gasket if yours has one. I tie the cap on the end with some fine wire or even plastic cable ties through a few holes.
As others have recommended, the bolt threads and the threads in the drive flanges need to be really really clean before assembly. This is one of only a few cases where I recommend Brake Clean for cleaning parts. Use care, because the higher-boiling solvents used in that stuff is 'fat soluble', and causes nerve and eventually brain damage. Skin contact, breathing, and especially eye exposure to vapors pose a serious health hazard.
Anyway, bolts go into the clean and flushed holes without the ties and get a few turns to support the joint. Cut and pull the ties, and the rest of the bolts go in. Tighten them progressively and evenly until snug, then do the final tightening with a helper with a foot on the brake. I assemble a few long extensions so I can sit outside the wheel and reach the tools through to get each bolt. That way I can rotate the disk from bolt to bolt, helper applies the brakes, and you get to torque the bolts in an alternating pattern as you might with wheel lug nuts. Once tight, I use a paint pen to make index marks on every bolt to the flanges so I can easily see later if they've moved.
------
The Good News is that this project happens here only a couple times in the life of most cars. I did mine at about a dozen years old, and the car is now closer to three dozen years old. They get at least an annual inspection, and I do watch for the telltale black grease-sling stripe on the surrounding surfaces. On my car anyway, the rear crossmember and the rear wheelhouse liner are the willing receptors of CV joint grease when a boot cracks. That grease is more than a casual chore to remove from the otherwise-pristine undercarriage and liner areas.
dr bob
1989 928 S4, black with cashmere/black inside
SoCal 928 Group Cofounder
928 Owner's Club Charter Member
Former Ex Bend Yacht Club Commodore Emeritus
Free Advice and Commentary. Use At Your Own Risk!
1989 928 S4, black with cashmere/black inside
SoCal 928 Group Cofounder
928 Owner's Club Charter Member
Former Ex Bend Yacht Club Commodore Emeritus
Free Advice and Commentary. Use At Your Own Risk!
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Tom
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You don't need to remove the axle nut on an '86 944 Turbo. Just remove the triple square bolts on the inner and outer ends and the axle comes out. You might need to get your muffler out of the way depending on what you have. There is a Pelican Parts how-to online for the 944 Turbo that says to remove the axle nut, but that's just flat out wrong for the 951. The axle unbolts from the axle stub when you remove the triple square bolts, so there is no need to undo the axle nut and pull all that out. Whoever did the work for that how-to must have had cars like the 928 in mind, but for the 944 it's just a lot of extra unneeded work.
Also, I always use new triple square bolts.
Also, I always use new triple square bolts.
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ROB III
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@notny41
I was digging through my files and found these:
Its pretty basic but if you haven't been in there before or gotten intimate with the underside of your car, this might be of some help.
Then there is this one that gives some additional tips for dismantling and what to expect when you break things down and particularly what to look for to reassemble,
This may be overload but more info and visuals always seem to help.
Have fun!
I was digging through my files and found these:
Its pretty basic but if you haven't been in there before or gotten intimate with the underside of your car, this might be of some help.
Then there is this one that gives some additional tips for dismantling and what to expect when you break things down and particularly what to look for to reassemble,
This may be overload but more info and visuals always seem to help.
Have fun!
Rob
89 944 Turbo
Musik-Stadt Region
89 944 Turbo
Musik-Stadt Region
