tlebovic

Yesterday was a hot, humid. overcast day so it was a perfect excuse to drive my 89 S4 Auto to a Christening in New Jersey. 60 miles of nice roads and hopefully little traffic. After about an hour, I had made it all the way to the church without a hint of trouble. I saw a shady parking spot so I came to a stop, shifted into reverse and was quite amazed that the car rolled forward! Step on the brake, put the car in Park, shift into reverse again and the same story. I then shifted into Drive, stepped on the gas with my foot on the brake and no forward motion either!.

At this point I coasted into a spot, called for a flat bed, and went into the church.

After a 3+hour ride thru the worst Sunday traffic at the George Washington Bridge, Cross Bronx and Major Deegan (it was the 5 Borough Bike outing and the Yankee game was letting out. Plus trucks can't go on the Garden State and we couldn't figure out how to get to the Tappan Zee Bridge.) we dropped the car off at my mechanic's garage.

I called today and let him know the story and he said "Hopefully it's just a bad seal and all your fluid leaked out. Could be as simple as that". Well, maybe for someone else but it's never that simple for me. He called back about 5PM and said that the case was relatively dry and the reservoir was full. He also said the linkage was moving and the car did try to creep forward when in Drive with high revs on the engine.

He didn't take anything apart but said from experience that if it's just clutch packs or bands it wouldn't be too costly and he'd rebuild it but once you get into metal parts the cost escalates rapidly.

Does anyone have a cross reference to the Mercedes part number? He suggested that we buy a rebuilt transmission from Mercedes and he'd bolt on the transaxle from my car. He recommended this approach because he's had trouble with other rebuilds and the transmission would be dyno tested from the factory. He also said that he got a transmission for a 500E about a year ago and it was appx $2500.

He also said that if I could find a used one with low miles it would probably last another 10 years for me and he'd be willing to install it. Of course without a warranty but even a rebuilt one would only give me 30 days and probably wouldn't cover the labor to R&R it again.

The numbers on the case are:
722 270 3201
722 360 0319 8945
if that helps identify it.

At this point I'm not sure what to do. My car is well maintained with 130k miles on it. I did an intake and cam cover refresh over the winter. Very good paint, nice clean interior, new Cup II 8 & 9" wheels, C&R radiator, recent rack, etc. But even on the best day it's only worth $15k so I'm a little gun shy about spending another $4k on top of what I spent over this past year. Nevermind what SWMBO thinks about "the family car". (Of course it's a family car - it has 4 seats! The kids used to fit back there!). I've also been a 928 owner for 14 years now and have been thinking about trading for a similar vintage 911.

Am I just dreaming about selling it for real value with a broken transmission?

Any thoughts? Anyone BTDT?

Tom
89 S4 Auto Black/Linen

linderpat

For a lot less, contact one of the 928 vendors and source a rebuilt from them (or a used, which may be more of a crap shoot, but the good vendors we use will help with this discussion). Have it shipped to your shop for installation (I do this all the time, and I don't expect the shop to stand behind the unit). Also, make sure it isn't just a broken half shaft.

Mrmerlin

Tom it would help if you could add your location to your signature.
Joey G is selling a 88 S4 trans for 700.00 I will see if i can find his screen name

Here is a thread he started just read through and PM him
https://rennlist.com/forums/928-foru...t-a-928-a.html

One other thing to consider is to check that the torque converter is turning with the engine running start the car and look in the trans grate its quite possible that you snapped a driveshaft and the trans is good

jon928se

Or a broken centre shaft (inside the Torque Tube)

taffelman

Used S4 Auto transmissions go for around 1000$ and re-built ones around 2500$. If you want to cut cost try to find a low mileage used one, it should last for years.

Landseer

The expert 928/benz trans guy in the NJ/NY metro area is Steve Cattaneo who sometimes posts here and has shops in NY I think outside the city.

In my research, some of his posts and others, the transmissions could fail to engage gear if the (weak) B2 piston jams or breaks. I have replaced one in-situ using instructions here (premptively, and thinking it would solve another problem). Cost was about $150 for parts. Read about the B2 and you may conclude it could be the culprit. In fact, I will link some pictures. It is rumored that if an 80s mercedes or one of these 928's fails to engage gears forward, that it is possibly the B2. Not sure if it would account for reverse loss also. Could be something totally different. I don't know enough except to help you start your research. Reverse loss by itself, after reverse engage lag persists for a while, is said to often be the reverse clutch pack breaking down.

89 auto trans has some upgrades over 87,88 trans. 89 is more desireable from shift point perspective. Somebody here would need to weigh-in on whether there exist any electrics within the 89 brain/programming that require inputs from the 89 trans and/or how to bypass in order to give you a wider year spectrum to swap. Probably can use 87 or 88.

An auto trans swap is doable.

Edit: to reinforce points made above, the drive shaft movement is the first place to start.

Gordak

I replaced my trans, I paid $700 bux for a used one and had to give mine in as a core. It's not the end of the world, there are worse things that can happen.
-Sam Johnson
78 Euro 5spd
87 s4 5spd

blown 87

Buy a used one and put it in, I think i saw one for sale here recently for 750.

Landseer

Here's some pictures, last of four is the contrast between old and new B2 piston, a known weakness due to binding --- you can see why.

Landseer

Selling for real money is hard enough running right now.

Tails

Tom,
Checked WSM for condition that you have described.

Condition: Transmission slips in all gears.

No or insufficient modulating pressure.

Correction:
1, Check modulating pressure, adjusting if possible.
2. Remove and service modulating pressure control valve.
3. Check and clean modulating pressure safety valve in shift valve housing upper section.

If this is the problem, it can be accomplished with transmission in the car. I would suggest that you consider taking it to a Mercedes Benz auto technician and get them to have a look, however, I would first post a question to Steve Cattaneo via this forum, as he is the resident expert on 928 auto transmissions. Steve also has a website, however, I don't have the address available at the moment. Some member may chime in with the address, which would be very helpful for you.

Tails 1990 928S4 Auto

WallyP

If I were anywhere near Steve's shop, that would be my choice. He is probably the most knowledgeable tech in the USA on 928 automatics.

dr bob

Get the car on stands and see if the torque converter is spinning at all with the engine turning. The outside of the housing turns at engine speed so it's easy to spot. You can rotate the engine with a 27mm deep socket (1 1/16" will do the job...), rotating clockwise only from the front. You can see the torque convretr housin through the grate in the front bottom of the transmission housing. Put a paint mark on the converter for reference so you can actually see if it moves.

This would be after confirming that the fluid level is close to normal in the reservoir, and that both halfshafts are still connected to the sides of the differential.

Does the car move with the gearbox in Park position? If not the halfshafts are the first place to look.

tlebovic

Thanks for responding.

The problem is not in the torque tube or the halfshafts - it's in the trans.

I'll probably end up buying a used one and have my differential swapped in if it's not from an 89.

Tom

Bill Ball

Very, very unusual for an AT to fail suddenly like this at this low mileage. I sure would want to have Steve Cattaneo's opinion before I did anything drastic. He owns Mastertech Transmission, the shop Wally recommended, and it's somewhere near you I believe (well, it's in NY). At least call him.

http://mastertechtrans.com/contact.html

I trust your mechanic is smart enough to know the pinion gear needs to come off your tranny and put on the replacement tranny if you are reusing your diff. This is a pain to do and I don't know why he thinks the diffs on replacement trannies are often bad, unless you have a limited slip diff. Standard open diffs are hard to hurt and he could easily inspect it for gear wear, backlash and small gear bearing play. Swapping diffs involves not only the pinion swap but some tedious setup, so if the replacement tranny's diff is not bad, it should be used. It is true that the 87-88 trannies have different rear-end ratios, if that is one of your concerns; 2.2 vs. 2.54 for 89.