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new transmission, new torque converter...still 14 miles/gallon. About to give up.

4K views 20 replies 17 participants last post by  Imanewbie 
#1 · (Edited)
So I bought my 2003 e46 at 158,000 miles....didn't know what to look for and was ripped off as the transmission was on the way out.

Symptoms very typical of only a faulty torque converter though - little motion below 2000rpms from a standstill, need to generally sit at 3000rpms to slooowly get up to 30mph...but once rolling less of a problem, and on the freeway economy is fine at around 30miles to the gallon.

City though, I was getting 12-14. Into the shop, who would not take the risk that it wasn't needing a transmission rebuild and wouldn't just replace the torque converter - but would fully guarantee the work if I did the fully transmission job.

I posted previously about this, and ultimately went for the full rebuild option - rebuilt transmission, main seal replaced, and new torque converter.

Picked it up - exactly the same. Revved it round the block, drove it straight back in asking what the deal was.

They thought it was fine (only having another one in exactly the same state to compare it to) - but I was then able to compare it my friend's same year model to verify that in that car, it did indeed immediately jump(/move) forwards when you start to depress the accelerator. Mine doesn't. Also idles low, so still symptomatic of TC problem?

Fortunately the guy who actually rebuilt the transmission offsite happened to be there - I got him in the car, drove around the block explaining the issue, he said 'yup, it's definitely the torque converter' - so back in the shop it went.

Because they had now guaranteed the work, they were in a way really good about it - took it back, gave me a hire car for a trip on the weekend, then a runabout for another week while they (apparently) put in another new torque converter.

Got it back again, with apparently another new torque converter, plus the transmission rebuilt for the second time.

Exactly the same again. Except this time making a low humming noise from the trans around 40mph. Got the runabout back (at this point I've been driving this runabout for the bulk of my time in California, longer than my purchased car originally).

This time, (again, apparently) they asked for a different (still second-hand obviously but rebuilt) transmission entirely rather than rebuilding my original one again. Plus another torque converter.

When I found it was exactly the same again (except the hum - that was introduced - was at least gone again), I just kept it - I'm an intern only here for a year and needed the car, and at this point I was 5 months into my internship and still didn't have a daily driver.

Does anyone have any clue at all what the hell is going on before I just have to give up and sell this? It feels like it would be a faulty torque converter. Obviously that's not the issue!

The shop is out of ideas and I don't really want to take it back and lose more time without at least being able to direct them with something else to check! I don't really have a reason to doubt they at least rebuilt the trans and replaced the torque converter, and they were pretty great about giving me a hire car (twice) and runabout twice for extended periods....

But it's sitting in the garage and I cringe every time I need to use it to do the food shopping! I get about 190 miles to a tank...... ><
 
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#3 ·
Did you ever see the transmission out of the car? When I was younger I went through a similar situation and found out it was all lip service. They never did the additional work they were saying they did.

Did you get your money back?
 
#4 ·
Yeah lip service. Theft with a smile on your face.
 
#14 · (Edited)
Yup - this - the transmission will still try to shift at the same rpms and under the same conditions until this is reset.

I recently had a similar prob in my wife's X3 - after a firmware upgrade for the tranny module and a reset of the adaptations for both the tranny and the transfer case the vehicle shifted fine. Yours would just deal with the tranny - since you don't have AWD.

Edit: - One last thing - these guys should know what they're doing but I found with one of my E46's that about a litre short of tranny fluid and the tranny was all over the place and the mileage sucked - especially city driving - also took a little while to get up to speed and it wouldn't go at all when freezing. I had to tilt the car and rev it while filling the last liter to make sure the transmission was really full.
 
#7 ·
30 mpg on highway is good. 12-14 around town is low, but could be reasonable in a congested town, with short trips.
I don't know how an e46 automatic bmw should drive. It could be they put in a "race" torque convertor - one that does not really engage until revs get to 3000 rpm or so. I'm assuming in your test drive it seemed OK to you. Not sure why it does not feel OK now. Seems nothing has changed even after dumping in more money. I'd drive it and quit worrying. Sell it when your visit is over.
 
#8 · (Edited)
There have been some really detailed explanations and tear downs of the ZF transmissions in the last 6 or 7 weeks, if this is what you have. Search "glhx and transmission" jjrichar, lloxley and others have really dissected it down. May help you or the shop, photos, diagrams, explanations etc.
You may have to be a little more assertive (a-hole) at this point. But both parties realize there's an issue.

Sent from my SAMSUNG-SGH-I317 using Tapatalk
 
#10 ·
Is it still requiring you to rev it past 2000 rpm to get moving?

If so, is it only the first time you drive it after sitting or all the time?
 
#11 ·
I think the mechanical side and torque converters are very solid on these trannys. You are probably looking at a fluid pressure issue which is solenoid, valve body and software controlled.

That aside, I'm not sure why your mpg sucks so bad. That could be entirely unrelated to the tranny but I can see how people can get hyper focused sometimes.
 
#12 ·
Yeah, what about those internal seals which hold pressure? Either they are playing you or don't know how to work on thus transmission and what seals may cause the problem...ever hear of a mechanic that talks a lot but never actually knows or can do what he says he can do?

I'd do some inquiries on his knowledge level and see if there's a seal kit available
 
#15 · (Edited)
Thanks guys - fluid not filled up and/or computer not reset could be possible...though if it drives the same as before and one of these fixes it, then I won't even know if it ever even needed a rebuild :p It really feels no different to when I first took it in. To answer the question, it's like this all the time, not just when cold.

If they never did any work at all, it would be a fairly elaborate scheme from a well-reviewed shop...

In any case, I've forwarded them this forum link, so maybe it will turn a fresh approach up!
 
#17 ·
You're in CA. Is traffic not atrocious there? Then is 12-14 mpg really that bad? You get normal MPG on the highway so your TC is locking up fine and your transmission isn't slipping. Any fanatics with autos want to go drive this guy's car and tell him if it's funny? I seriously would if I was nearby, but I'm across the country.
 
#19 ·
As I said, I directly compared it to my friend's car of the same year and model. The difference is obvious within driving it 5 metres in the car park. I live in a reasonably light traffic area, they usually get about 20mpg around town anyway.

I also wouldn't ever expect 12 miles per gallon to qualify as 'not that bad' given the last SUV 7-seater I hired got 16/g fully loaded around the same area ;)
 
#18 ·
Make sure your AT was filled correctly... You don't fill these trannys like you do normally and refresh TCU... Did you take it to a shop that specializes in BMW? if not there was your first mistake =)
 
#20 · (Edited)
new transmission, new torque converter...still 14 miles/gallon. About to give...

There's a chance your cars have different transmissions. One ZF and one GM depending on month of manufacture. That wouldn't explain the mileage difference though.
Are any of your brake calipers stuck?

Edit: duh if that were the case you wouldn't get 30 hwy. doh
 
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