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Tuesday, April 23, 2024

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Doug Vetter, ATP/CFI

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Friday, May 12, 2017

More Transmission Rebuild Research

I've spent some time over the last few weeks reading the ATSG manual, checking out relevant threads on various forums, watching videos on Hiram's YouTube channel to pick up general tips and practices that apply to all transmissions and researching the various parts and special tools required to do the work on the 4L30E specifically.

I'm still not 100% convinced I can do this work in a reasonable period of time or at less cost than a professional but as I can now identify most of the components in the transmission by sight alone and visualize most of the procedures needed for the overhaul as well as many of the typical failure modes, it's fair to say my knowledge has increased dramatically and my justification for DIY will now largely depend on factors other than knowledge, such as time available, finances, and risk tolerance.

If you think I'm considering a DIY overhaul to save money, you'd be right -- and wrong. While the master overhaul kit for the 4L30E is less than a tenth of the cost of a professional overhaul the kit does not include items that can trash a fresh overhaul if not replaced -- like the solenoids or bushings. The list of special tools I'll need is around $500 and growing, and I'll likely have to outsource some labor for various operations (cleaning the case, replacing the bushings, etc.) so figure another $200 for those services.

So I'm approaching a grand and I haven't actually inspected the thing to learn if anything else will need to be replaced. For example, this transmission has known issues with its third clutch housing. I found a new-old-stock replacement but it's $100 on its own. Another sore spot is the servo bore which can wear and allow oil to leak past the pin. There are servo replacements and repair kits available to remedy this issue, but they're not cheap. And heaven help me if the pinion end play on the planetary carriers is out of spec as there is no repair procedure for those -- they must be replaced and I haven't located a source for those yet. I'm not sure there is one for a transmission this old.

When I factor in what will probably be at least 30 hours of labor because this is my first time through I think it's safe to say that, while on paper I'll probably come out $1000 ahead, in reality I'll likely be in the hole by at least that much. But on the other hand, I'll know how the job was done and learn a valuable skill in the process.

I did find a few more local transmission shops that seem to have good reps so I plan to approach them with requests ranging from cleaning and bushing replacement to a complete overhaul. I also plan to ask if they would be willing to let me sit in on the process with their tech so I can have my cake and eat it too -- a quick overhaul for predictable money AND with video of the rebuild process for the blog. My guess is most shops will shrug at this, but perhaps one of them will see it as beneficial to their business -- because that's the shop I'll choose.

Servicing Fixture and Mounting Adapter

I found a reasonably priced source for the original factory transmission servicing fixture (Kent Moore J-8763B). The problem is that this fixture is intended to be inserted into a holding clamp designed to be mounted to the edge of a table. It doesn't take a degree in physics to realize that the table must be heavy enough to counterbalance the weight of the transmission or be bolted to the wall or floor so the whole thing doesn't fall over. I don't presently have such a table and I think it's fair to say that my brother wouldn't want me drilling holes into his shop's newly finished, heated floor in any case.

This led me to research an adapter that would allow me to mate the fixture with an engine stand instead. While I did find what I thought was the perfect adapter, the company that made it (Rack Up) apparently went out of business several years ago and no other company has stepped in the fill this niche. So it appears that if I want to use an engine stand to hold the transmission I will need to have an adapter custom manufactured. That is, fortunately, less than an hour (including drawings) in Solidworks once I have the necessary dimensions, and probably less than an hour of a machinist's time, but it won't be free, that is sure.

Transmission Part Number History

While researching rebuild kits for my transmission I discovered that there are two different kits available for the BMW applications of the 4L30E and these are based on the model year of the car. Most (but not all) seem to indicate 1997 as the cutoff point between the two kits.

Normally this would be an open and shut case -- I'd know what to buy based on the model year of the vehicle. Unfortunately the original transmission was replaced ten years ago with a remanufactured part from BMW's inventory so I can't be 100% sure of the exact part number in the vehicle at this time. For this reason I had to do a bit of research to see if I could identify the same 1997 cutoff point the industry recognizes in BMW's part system.

Realoem.com reveals the following history for the 328's automatic transmission:

I last replaced the transmission in February 2006 and I think it's safe to say that by that time the 651 part was the recommended replacement but unless BMW had already gone through its inventory of earlier part numbers before my replacement unit was installed there's no way to tell exactly what part number is in the car.

However, based on the fact that units after 1/97 are not exchangeable with prior versions and BMW gave the newer transmission a new model code likely means that the A4S 310R is what the industry recognizes as the late model version of the transmission. Thus, I should be safe buying the "97+" rebuild kit.

Overhaul Kit Options

The industry seems to have adopted a nomenclature for service kits used in the rebuilding of transmissions. Briefly:

Several companies make kits for this transmission. Transtar is perhaps the most well known. I contacted them with this information and they gave me their part number for the Master kit: 24006EAF. If there is a downside to the Transtar kits, it's that they appear haphazardly packaged -- they basically just throw all the parts loose in the bag and leave it up to the technician to figure out what goes where. Much of this is obvious from size and form, but to a DIYer like me, looking at dozens of similar o-rings and other seals with no identifying information is intimidating to say the least.

Seal Aftermarket Products markets the Toledo brand of kits and these are, by comparison, awesomely packaged. Each part in the kit comes packaged in its own sealed plastic bag with a clear description of the intended function and / or location of installation. Check out Hiram's video on his 4L65-E rebuild (Part 1 and Part 2) for a good overview of the Toledo kit. Incidentally, as a pro he doesn't find the separate bags helpful, but watch the video and then judge for yourself.

Torque Converter Overhaul

Modern torque converters, including the one in the E36, have a lock-up feature whose aim is to eliminate the losses inherent to fluid coupling by locking the crankshaft to the transmission much in the way a manual transmission clutch does. You can most readily recognize this in the E36 during deceleration from highway speeds. As you pass about 1500 RPM with the brakes applied the engine RPM will suddenly drop to idle. That's the torque converter clutch unlocking.

So, just as there are wet clutches consisting of alternating steel and friction materials in the interior of the transmission, there is another such clutch pack in the torque converter. And like the clutches inside the transmission the clutch materials in the torque converter wear out eventually. So this means replacement of the torque converter clutch pack is required as part of a proper transmission rebuild but, unlike the transmission, the torque converter is welded shut so it must be professionally remanufactured.

While Google was surprisingly worthless when it came to searching for torque converter remanufacturers I read a few forum comments favoring Precision of Iowa. A search on their website by vehicle indicated there several different flavors of torque converters designed to mate with the 4L30E and they vary by, among other things, stall speed. Their search engine did not, however, provide a BMW part number cross reference so I could not tell what variant of the converter belonged in my car.

When I called Precision a friendly rep picked up the phone on the second ring and told me that GM typically embosses the converter housing with a code that indicates the configuration of the converter and I would need to know that number before ordering. As they deal through distributors they could not provide a price but they gave me my local distributor's number so I called them. The distributor confirmed the comments of the Precision rep and informed me that the price would be $150 after the core charge is refunded. Worst case lead time was 4 days from Iowa in the event they did not stock it locally.

Strictly out of curiosity I verified BMW sells the converters but they're $1600. The only thing more insane than BMW charging that much for a remanufactured converter would be paying that much. The sad thing is if I could order the transmission without the converter I'd probably do that instead of rebuild it myself, as it would be around $3K and therefore not much more than an aftermarket rebuild but with an all-important labor warranty included. However they only sell the transmission in conjunction with the converter so it doesn't make sense.

Pistons Ordered

And so it begins.

After a few more pre-sales questions with Steve of Top End Performance I finally decided to place the order for a set of stock replacement 4032 forged pistons yesterday. I also decided to go ahead with the thermal coat for an additional $138. This will likely be the most expensive single part (or set of parts) I buy for the overhaul assuming my crank and head are in good shape. Unfortunately I won't know for sure until the engine is disassembled.

While the engine work won't likely start until July the lead time of these parts demanded an early order. Over the next few weeks I'll be picking up various tools and equipment and setting up my workspace in my brother's garage. Once that's ready I'll call Autohead to have them send me the box I will use to ship them the head, call my machinist to give him the heads-up he requested, and most importantly -- get on my tech's schedule. More to follow soon...

Mileage: 265600