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I have my 88 5spd on jack stands for some other repairs and I’m thinking This would be a good time to change the transmission and differential fluid. I have the STA gear oil that was recommended by Greg Brown and respective crush washers as well as a fluid pump.
My first question is, Do I need to heat up the transmission fluid prior to changing? And if so is it possible for me to do it on the jackstands by spending the rear wheels with the engine in gear? Or is there something that I should drive and then put back on stands and then change?
, Do I need to heat up the transmission fluid prior to changing? And if so is it possible for me to do it on the jackstands by spinning the rear wheels with the engine in gear? Or is there something that I should drive and then put back on stands and then change?
My second question is should I ensure the car is tilted such that I drain the front of the transaxle, Or is it fine to have the car relatively level?
My third question is just how level should the car be when filling the transmission do I need to ensure it’s perfect for approximately level?
I read on the forums that some people have difficulty getting the drain plugs removed. Any tips on getting them to break free? Should I hit them with a heat gun first? Should I blast them with PB blaster? Should I tap them with a hammer?
I wouldn't worry about warming the fluid up. I would, however, let it drain for a while.
My 85 has drain plugs at both front & back. So being level isn't an issue, and you don't need to tilt it to drain it better. I don't think it would hurt, but it's not needed.
The drain plugs can be a pain. Have you had them out before? If not, you are at the mercy of the (potentially) ham handed gorilla who tightened them last.
First off, make sure you take out the fill (upper) plug first. Make sure you can fill it back up before you drain it.
They are big allen head plugs. Standard procedure for removing an allen applies.
Take a pick and get all the crud out of the hole.
Put the socket in and give it a couple of decent whacks with a mallet. This seats the tool in the hole and 'shocks' the threads a bit.
When turning, start easy and add pressure slowly. Do NOT let it slip. If it starts to slip, back off.
If it doesn't want to come loose, try some penetrating oil, give the back of the ratchet a couple whacks with a mallet while putting turning pressure on it, put some heat on the trans case. You don't want to heat the plugs, you want to heat the metal around them. You may want to hit the plugs with 'cold spray'. (think about it: you want to expand the case - heat and contract the plug itself - cold).
When putting the plugs back in, they don't need to be super tight. Just until the crush washer is squished down (use new ones). Torque spec is really low. My copy of the tech specs shows 22 N-M, which is about 16 ft lbs.
They way I have done it is to go for a drive, jack it up from the rear cross member, insert jack stands, (leave the front on the ground) and drain from the front drain plug. You can remove the rear drain plug to remove debris from the magnet but no oil should come out because of the angle.
The oil comes out FAST and will land at least a foot forward of the drain so be ready for it. The above is good advice on the drain plugs. The tightening torque is surprisingly low but it will work.
I will be curious to hear your thoughts about the Sta-lube. This is what is in my gearbox now but I am unsure if it is any better/or as good as Mobil 1. I had flushed my gearbox out with cheap CARQUEST gear oil and strangely, I think that gave the smoothest shifting but it is not rated for limited slip. https://shop.advanceautoparts.com/p/...hTerm=gear+oil
I'm new to the 5 speed 928 game (I've only had mine in my car for a total of 8 days so far), but so far I've had both STP conventional 75w90 limited slip and mobil delvac1 75w90 non limited slip (no lsd) and it shifts great with both of those; no crunching.
Maybe it's an early/late car difference, but my 78 didn't have crush washers, or even a shoulder on the plugs to have seated against a washer.
I was not lucky with the rear drain plug on my car, it wouldn't budge, no matter what I tried.
I'll probably try more aggressive methods next time, but will have a replacement plug on hand before I do so.
Thanks for all the recommendations. I started with attempting to remove the fill plug but it is stuck hard. @waynestrutt recommended that I heat the rear panel with a torch and spray the plug with cold water or use an ice cube to help break the bond. I'll give that a try today. But first I need to drop the custom exhaust because one of the pipes is preventing access to the lower rear plug and better overall access to the fill plug.
They way I have done it is to go for a drive, jack it up from the rear cross member, insert jack stands, (leave the front on the ground) and drain from the front drain plug. You can remove the rear drain plug to remove debris from the magnet but no oil should come out because of the angle.
The oil comes out FAST and will land at least a foot forward of the drain so be ready for it. The above is good advice on the drain plugs. The tightening torque is surprisingly low but it will work.
I will be curious to hear your thoughts about the Sta-lube. This is what is in my gearbox now but I am unsure if it is any better/or as good as Mobil 1. I had flushed my gearbox out with cheap CARQUEST gear oil and strangely, I think that gave the smoothest shifting but it is not rated for limited slip. https://shop.advanceautoparts.com/p/...hTerm=gear+oil
I used Redline 75w-90 gear lube with a qt of their MTL (manual transmission lube). My '82 suffers from a a worn 2nd gear synchro and the combo definitely improved the notchy-ness on the up shift.
Are your plugs 17mm or 10mm hex? In my collection I have a 17mm hex key, popular with the early air-cooled cars, that's a brute. Made when tools were made from real metal. I can get it to you in a P-M box if it will help. Large industrial wrench a couple feet long wraps around it for leverage. Else a 3/4"-drive adapter and a 4' long cheater. Something will move... Let me know. It's snowing now, but should be clear over the passes in a couple days if I need to bring the bigger tools.
For others playing along at home... It's real tempting and easy to over-tighten the fill and drain plugs in the cars. Engine oil, coolant galley drains, auto and manual gearbox drains, differential drains. Almost all are fitted with aluminum crush washers that need to be replaced if they are fitted dry. Otherwise the temptation is to keep tightening until they no longer drip, and they will likely drip at recommended if oil gets on the washers prior to tightening. Kind of like the way Stan recommends DeOxit and DC-111, I keep some Teflon thread sealing paste handy for bolts that have liquid behind them. This is Oatey paste in the grey-and-white can, from the plumbing aisle at Home Depot. Anyway, a bit of that in the threads does a good job of blocking liquid flow through the thread, plus it adds a lubricating film that limits how the steel plug and the aluminum hole become one with corrosion. Add some to the actual sealing faces on the casing, washer, and the plug itself, and you can eliminate the galling that's inevitable with tightening the bolt enough to seal. The net result is a plug that seals fine, comes out easily next time, and doesn't need a new washer every time. Less risk of galling on the threads too. You use less tightening torque since you get the same pressure with the lubricated threads, and actually need less pressure to maintain a seal with the coated washer. For the gearbox plugs and the galley drains particularly, the reduction in tightening torque will save you a bunch of anguish around fracturing the threaded block bosses for the drains. Or trying to add enough heat to a big oil- and steel-filled aluminum gearbox casting to get differential expansion with the drain plug even with an ice cube inside. (Don't bother, you can't with home propane or MAPP gas torches.)
Thanks for the offer bob, my plugs are Allen keyed. I’ll report back today after I drop the exhaust on my head and break my Allen socket from the 300ft lb of torque I’ll need to remove them.
You answered my question on using the sealing paste. Good thing I have some from my coolant change project.
I wouldn't normally recommend thread sealant for a differential plug, but if you're going to use it, then you should use the right stuff. Loctite 567 would be the right stuff. Designed for automotive applications, withstands higher temperatures than regular thread sealant, is much stronger, and overall light years better than anything you'll find at Home Depot.
This is the same thread sealant recommended by Eaton for their Class 8 truck transmissions. I've used it in that and other applications and it's never let me down.
Loctite makes a very wide selection of sealants and thread lockers. Most people don't even realize that there are different grades and types of "blue" and "red". Let alone the grades of thread sealants available.
Again, I don't recommend thread sealant on the light duty differentials like the 928's, but if you're dead set on using it, then don't use the stuff from the hardware stores. Use Loctite 567.
Also, if you end up needing to put a lot of force on the plugs, use an impact hex driver. Much less likely to break off in the plug and cause even worse problems. That driver, plus a proper breaker bar, and you will get most plugs out. I've also had a lot of luck using an impact gun to break loose stuck plugs, but that may be a step beyond what you're comfortable with.
The Oatey product I recommended is good to 500ºF in liquids, at up to 10,000 PSI. In my amateur opinion, it should be more than sufficient for the transmission (or any other non-fuel fluid connection or plug in a 928) drain or fill plug duty.
I agree that there are certainly specific products that have specific recommendations for or use, with duty ratings that may be overkill for this particular service. This is not one of those cases.
Challenges also include the idea that the LocTite 567 may not be readily available in the middle of a system service. Is it on the shelf at the chain POLAPS? I don't know. I bought the Oatey at Home Depot for under $5 at least a decade ago.
Looking at Amazon, at the other end of a brown-truck ride, a 250ml tube of LocTite 567 is a mere $68, and shows an upper temperature range of 400ºF. From that same Amazon source, the 8oz can of Oatey 31231 with the brush is $12, with that 500ºF limit in liquid service. Even disregarding the cost component, the technical info suggests that the Oatey stuff is better. Further, I'll share that I like the much thicker paste form of the Oatey product. But that's a personal preference issue. The can lives in a little Ziploc bag in the chems drawer, because it's insidious -- sticks to everything. Fair warning.
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Virtually all thread sealing pastes and tape products are originally intended to help seal tapered pipe thread connections. In that service, there's a mechanical pressure against one face of the thread, plus the outer edge of the thread. Leakage happens when liquid passes along the unloaded face. In a straight threaded plug application like the subject gearbox drain, we depend on the paste as much for lubrication and protection as we do for sealing. Further, the coating on the sealing faces of the casing, plug and the washer protects from galling, where dry metal is "smeared" by the relative motion of the various parts as the plug is tightened. Ditto on the loaded thread face, where friction includes wear. Since you can get a good seal on the threads and at the sealing washer faces with lower torque, there's less chance of "pulling" the aluminum thread in the case while overtightening for a dry seal.
In the end, I don't really care which if any product folks use, particularly if it's on something that I will never get to work on. Meanwhile, I gently curse the ignorant or inconsiderate person who is responsible for stuck plugs, broken bolts, nuts, and other fasteners that were not prepared well. When a drain plug comes out with the aluminum case threads attached or with the hex too round, it may be slightly more than the gentle curse. As often as not, I'm going to be the next person to work on something I'm working on today. It makes perfect sense to me to use a little extra care so I don't risk having to curse myself some day. Plus, after more than a casual amount of that gentle cursing over the years, I made a promise not to be that a$$hat PO or short-cut tech for the next owner.
For what it's worth, Loctite 567 is available at most local auto parts stores, and I also found it for ~$9 on Amazon.
I have some on hand from a GM engine rebuild years ago, where some of the bolts penetrate the cooling jacket, and require a thread sealant.
09-29-2019, 02:47 PM
Tips needed for 5spd fluid change
