Transmission Advice - GM A5S 390R

[stewey]

My transmission slips a bit on cold starts and the other day it slipped a bit on a hill start. From what I've read these transmissions tend to fail between 80-100k miles due to soft valve bodies and insufficient pressure leading to excessive wear and then boom. Mine has 90k miles on it. I think a lot of us are in a similar position with these 3.0 models.

"If you already own a vehicle with this transmission, keep the above information in mind and try to catch the problems before they destroy the transmission."
Beware Of the GM/BMW 5L40E Transmission - ETE Reman - Keep An Eye Out For Problems With The 5L40E Transmission

"…the mechanical problems are the result of reduced hydraulic pressures caused by wear & subsequent leakage in the hydraulic valve blocks."
http://www.xoutpost.com/bmw-sav-foru...-teardown.html

So far I have done an EGS upgrade. That has helped with the cold start delay. But what else should I do? I'd like to keep the truck for a while and a new or rebuilt transmission is about $5k

I can do fluid and filter for $250
I can get a rebuilt valve body for about $1000.
I can wait for it to go boom for $0 now, $5k later
Other options?

What should I do? Will a new valve body significantly extend the life of this transmission?

Thanks!
Stew

[stewey]

Another option I am considering is to do the fluid, filter and TCC solenoid. I imagine this would add $150 or so. Any opinions?

[JCL]

I would be checking the fluid level (properly, vehicle level, temperature to spec) first. Low fluid level is a potential cause of your problems.

I don't think it is right to say that these transmissions fail at 80-100k. There have been failures, but they are by no means concentrated in that mileage band. They tend to be all over the place. That suggests to me that the failures are not related to the transmission wearing out as much as they are due to random failures of wiring harnesses, sensors, actuators, and so on. Valve body seals can be a part of that, certainly.

This is supported by the observation that different transmissions in these vehicles fail more often that we would like to see, even though they are from entirely different suppliers (GM Powertrain vs ZF) and are different models (5 and 6 speeds). The common elements are the controls, wiring, etc.

If the fluid was not burnt when I checked it, and the level was correct, and if the problem persisted past a couple of occurences, I would be looking to the valve body before overhauling the transmission. I am not clear on why you jump to $5000 for a transmission in your analysis, as that sounds like a full exchange. It would likely be cheaper to have your own transmission rebuilt, and if you don't drive it to destruction with overheating and slipping, then you are unlikely to need that many parts for it.

[stewey]

Thanks JCL, I checked the fluid before I did the EGS upgrade. The level was good and it looked clean. Definitely not burnt.

It is nice to hear that you have a more positive opinion of this transmission. The research I have done paints a more dreary picture. For example:

"You may have seen my post on stripping down a broken 5-speed GM 5L40-E automatic transmission and it is clear from the comments on this and other L322 forums that this model ... has an unenviable reputation for failure usually between 80,000 & 100,000 miles."
‘Sonnaxification’ of GM 5L40-E valve bodies

When you say you would look at the valve body, what would you do? Are you suggesting a more modest repair? I was thinking that the bill for any type of valve body work would be close to $1000 (the cost of a sonnaxified unit).

[JCL]

The threads you are referencing are about an X5 diesel. The diesel 3.0 had much more torque, and experienced a relatively high number of failures with this particular transmission. BMW subsequently switched over to a stronger transmission for the diesel. I don't think that the diesel transmission failure rate is applicable to your 3.0 gasoline engine. I think that the general information about that transmission contained in RRPhil's excellent posts is very good.

If you are not going to be working on it yourself, I would find a good independent transmission shop familiar with this model of transmission. I would ask them to diagnose it, specifically referencing the 1-2 shift issue, and would lean towards trying a valve body repair or replacement (if that is what their diagnosis pointed towards) before beginning a transmission overhaul. If they can't find a likely cause, I would consider a transmission overhaul of my own transmission (not an exchange).

I can't point you at a specific likely cause (other than the solenoid and accumulator spring associated with the 1-2 shift) but I would be trying to test that circuit before removing the transmission. The fact that your fluid isn't burnt suggests you don't have a problem with clutches slipping, but rather with a single circuit relating to the problem shift. All in my opinion.

I wouldn't change the fluid on the faint hope that that would resolve the issue, but it is a gamble that you may want to take based on your own cost/benefit evaluation. It is certainly the cheapest place to start.

Hope that helps. Good luck.

[stewey]

It makes sense that the diesel would put more strain on the transmission. Thanks for pointing that out. I don't have a 1-2 shift problem that I have noticed. Mostly a park to first or a reverse to first problem and two or three times some slippage on steep hills when cold.

I won't be doing the work myself. My experience is limited to brakes and control arms, etc. Can the circuits be tested without dropping the pan? Can they be tested with the valve body in the trans? At any rate I'll chat up a local trans shop and report back.

Thanks again!

[JCL]

Sorry, the 1-2 shift issue I was thinking of was in one of your links.

Some tests can be done without dropping the pan. Second step is checking the valve body with the transmission still installed.

Let us know what they find out.

[stewey]

Quick update. I talked to one of the local transmission shops. Based on my description of the symptoms and the age of the vehicle he suggested I rebuild the transmission. He said whatever is wrong is internal and there isn't much he can determine without pulling the transmission from the vehicle and tearing it down. Ballpark he said $2000 labor plus parts. He couldn't guess at how much parts would be as he said it would depend on what needs to be replaced which he won't know until it's torn apart and can be inspected and tested out of the vehicle.

I'm not convinced my problems are severe enough to warrant this yet. He warned that if I 'melt' the transmission, the cost to repair will go up significantly. So, I need to factor that in.

Still collecting more info, so opinions and suggestions are welcome!

[absentmathis]

^ I think you can do better than that. Heck, Aamco does free scans and diagnostic. I bought an e53 that I thought needed a new trans. A non car-savvy buddy told me they do free diag, so I took it in and was extremely impressed with their car-specific knowledge. I mean a national chain and a German car? I was very surprised. Like any shop, service depends on how good their techs are, but my advice would be to have someone knowledgable look at it before making any big decisions.

[stewey]

Thanks absentmathis, we don't have Aamco here but I will get a second and possibly third opinion. I will report back!