hillpc

So I'm into the 5HP24A trans disassembly now and found the expected broken A drum where the snap ring sits. (I had already replaced the valve body section with pressure regulator and had another section of the valve body welded up where it had cracked.) It seems this trans has been worked on before, as it has a tag on it from Wolf Transmissions Toronto, as well as other evidence (looks like it was painted silver, and a few slightly buggered Torx heads). Car has 180K miles on it. Clutches all look good. The F piston, which I understand is another weak part in these transmissions, looks like new. (Well, what I would imagine to be new; never actually seen a new one.)

Now I'm looking to replace the A drum and have seen several that are supposedly upgraded replacements for original drum # 1058 0270 040. But the ZF spare parts catalog says 1058 270 036 is used in trans 1058 020 004/007/009. I have 004 trans; I think that's the same as trans code DPZ. (The catalog says the 040 drum is for trans 1058 020 014/015/021/029/030/031/033.)

Could I use a replacement drum meant to replace 1058 270 040? What's the difference between drums 036 and 040?

I also saw an upgraded drum listed on cascadetransmissionparts for 1058 270 036; it has a funky-looking snap ring described as an alligator-style snap ring. Says it's tricky to install. Anybody have any experience or comments on this? The photo below is from ZF Heavy Duty Transmission Input Clutch Drum Design BMW Jag Audi 5HP24 5HP24A | eBay

tanya_charbury

I'm sorry I didn't see and reply to this before; by now it's probably too late to help you (unless you work at the same slow pace I do) but maybe what I learned can help others.

I had the same questions as to the 1058 270 036 vs. 040. I learned that this type of transmission was used in the early D2 Audi A8, before it was used in the C5 Audi A6. The early variations of this transmission used a particular design of clutch A drum, part number 1058 270 036, and that was superseded by the interchangeable and slightly-improved 1058 270 040. As I understand things, ZF recognized that this was a high-risk area, and a good place to improve.

As the nice people at Cascade explained things to me, the clutch "A" drum failing was initially thought to be due to a problem in the drum, and ZF wasn't the only one to consider this; more than one aftermarket vendor was tempted to make a replacement drum not least because at the time ZF was out of stock as to this drum and wasn't making any new ones. Right when the aftermarket vendors had invested in the tooling etc. and were bringing their units to market, ironically, ZF had started making these parts again too so then buyers had several options. As explained to me this wasn't intentional timing on the part of ZF; they'd just been overwhelmed trying to keep up with demand for the 6HP units, and that's where their focus was. The aftermarket vendors made a point of beefing up their designs relative to the ZF units. Quick plug for Cascade: they're not just savvy and nice but also very responsive even on weekends and after hours. As to the Cascade unit, I didn't have a hard time assembling it but I don't recall the details any more; it's been a while.

Eventually it became apparent that it doesn't matter how strong a clutch "A" drum is; the hydraulic pressure spike from a worn pressure regulator will eventually pretty much destroy anything (though I haven't seen that happen to a Cascade unit, I do have a lot of respect for hydraulic pressure). Hence the need to renew the pressure regulator in the lower front housing in the valve body -- ideally preemptively.

Sorry to ramble; I kinda got OCD with this subject.

One of the pictures I uploaded shows a blown ZF clutch "A" drum from a transmission I disassembled; the other shows the ZF vs Cascade unit (the latter to the right). Cascade doesn't make them; they sells them and are very savvy as to various sources, and they helped me avoid the made-in-China variant.

hillpc

Actually, the job was interrupted months ago (and tying up my lift) by a honey-do bathroom remodeling, so the trans isn't done yet. I have bought the alligator-style drum from cascade and installed it. My original broken A drum is shown in one of the attached photos. I also found a crack in the upper valve body (maybe also from the pressure regulator spike?) and had it welded up by Eriksson Industries in Connecticut. Nat Wentworth there seems very knowledgeable about these transmissions and was quite helpful. I also bought from them a valve body with upgraded (oversize) pressure regulator, as well as a new manual valve (selector valve in the valve body), which is moved by the shift cable mechanism when selecting the range. The manual valve would jam in its bore and could not be moved out of Drive after the car warmed up while driving/testing it in limp mode, but after cooling down it was OK. The new manual valve cured that (but obviously not the limp mode). It's aluminum, not plastic. Nat said it seems the plastic valves absorb water and swell.

Nat told me a story about how the pressure regulator breaks the A drum. According to him, driving with the old style regulator eventually wears a ridge into its bore, especially when driving granny-style, and then when one goes full throttle, the regulator valve hangs up on the ridge, can't slide past it, and thus can't relieve the high pressure generated from the pump running at high rpms. This breaks the retaining ring groove off the end of the A drum, as seen in the picture.

So the trans is still on the bench, about 95% assembled. Valve body, pan, and some easily assembled gears are left to install. The bathroom will be done this week, at which point I'll get back on the Audi.

There's a wealth of experience on these forums. Thanks for commenting.

tanya_charbury

I'm relieved to hear I'm not the only person whose projects span months on hold.

Wow, your broken A drum picture really tells the story. Thank you for posting that.

Welding that crack in the housing is an impressive-to-me feat, since it's aluminum, as far as I know. Is it okay for me to ask you what Nat charged for that? I know his prices are very reasonable; I'm just curious since I have a few of these valve body housings with the not-yet-cracked examples of the part that cracks (I've started collecting them).

Nat Wentworth of Eriksson Industries in Connecticut is a rock star, as far as I'm concerned. He's savvy and nice.

Wow, that's SO interesting about the driving style that triggers the tragic series of events that blows out the A clutch drum. I didn't know that, but it makes perfect sense now that you explain it.

I'm cheering you on as to wrapping up the transmission project. If you need moral support feel free to message me directly. :-)

Since the "A" clutch from a ZF5HP-24A looks a little like the torch of the Statue of Liberty, here's my homage to her.

hillpc

It was $135 for the aluminum welding repair, but I don't remember the shipping cost breakdown. Uncracked upper valve bodies themselves may be available, but I ran into uncertainty with part numbers so I simply had mine welded.

I like the Statue of Liberty photo.

tanya_charbury

Thank you for the information, and kind words. :-)

ocles_inc

Hello again from Tanya. It's official. I have signed up my company (ocles_inc) to become an official paying Audi World vendor. As such, I wrote an article about the cracked casting 1058327059/1058427059. I used your picture; thank you again for your kind permission to do so. Since you seem very savvy about this transmission, I would greatly appreciate any feedback you would be willing to provide including as to how I tried to obviate part number confusion. Thank you!

hillpc

I'll have to try to find what valve body part number confusion I had, that led to me getting mine welded instead of just buying one. Maybe you've cleared it up!

I assume you have the ZF parts list and diagrams document.

I have more pix of the cracking, including the backside, but never went so far as to figure out what a leak in this particular passage would do. Too much brain work for something that would only be of academic interest to me.

ocles_inc

Since your insights have greatly helped me, I'd be happy to hear if my 1058327xxx vs. 1058427xxx insights are helpful to you in any way.

I do have the ZF Spare Parts Catalogs for the ZF 5HP-24 and 24A and I bought the formal ZF 5HP-24 repair manual too, which covers much of what would go wrong with the 24A, the main major difference being the Quattro drive mechanism.

What I saw in these documents is in large part what puzzled me. I understand the skill set involves in copying and pasting the part numbers from someone else's document but I greatly prefer to squint at the physical parts personally and have first-hand knowledge of the part. That ties in with the premise that I love deeply understanding what I sell. With these transmissions that's been quite the challenge which (dare I admit it) might be what draws me to them. And, while looking at the physical castings in my hand, I would always see the 1058427xxx part numbers and never the 1058327xxx part numbers, so I finally gave up and asked. I emailed Nat Wentworth, at Erikssson Industries, who is a ZF distributor, and very helpful and patient. I asked him to enlighten me, so he gets the credit for this issue having been clarified.

> I have more pix of the cracking, including the backside,

I would love to have those pictures too please, please with permission to use them like you graciously gave as to your other ZF 5HP-24A pictures.

> but never went so far as to figure out what a leak in this particular passage would do. Too much brain work for something that would only be of academic interest to me.

Once I have things more under control, I look forward to installing a known-to-be-bad-in-a-particular-way component into an otherwise-healthy project car and using that to isolate the resultant symptoms so I can more helpfully enable the people who need this part to identify themselves.

Thank you for all the benevolence.