Excessive AT 2-3 flare & fluid level (722.3)
 

Greetings Benzizens,

So recently I've been convincing the wife how much a transmission rebuild is in order by demonstrating a horrible 2-3 flare on my 95 E420 (722.366 AT) in the morning. Until engine coolant reaches 80 *C, shifts are jolting and the 2-3 races a couple thousand before catching. My copy of the 722.3 ATSG suggests worn clutch packs and a full rebuild.

Hold onto your wallet, folks.

Turns out my diagnosis may have been proven wrong this weekend. When all this shifting nonsense started a few months ago, I changed the ATF and dropped some Lucas in for good measure. Cranked the modulator down a bit and the problem seemed to resolve itself. About one week after that, the 2-3 flare returned with a vengance. Fluid level remained the same (topped off) and so did the predictable morning shifting.

This past weekend, I decided to do something my father warned me never to do -- added 500ml of fluid to the already "full" level in the housing. Guess what? Shifts softened to where they should be per the modulator, no 2-3 flare, and the transmission is well-behaved now even when cold. Dipstick still shows more fluid than needed... but the extra fluid seems to have solved the problem.

Questions:

a. How do you explain the effects of extra fluid? Even with leaky internal seals, there is no reason (IMHO) why extra fluid should have done anything positive.

b. Given the apparent resolution, was my transmission ever actually "flaring" during shifts the past three months? In other words, should I be worried about the clutch packs even with clean red fluid and just a slight burnt smell?

Many thanks in advance,
-DM

Three days and over 40 views without a comment? Surely someone out there has a clue about these transmissions...

-DM

OK, OK, I'll jump in. I have two thoughts on the matter.

Slow, flaring shifts and slow engagement when shifting from park/neutral are typical symptoms of low fluid level. How certain are you that you're reading the fluid level correctly? It can be a bit tricky. Fluid from the dipstick tube (as opposed to the pan) gets on the dipstick and gives a false high reading. Since it can be difficult to see good, clean fluid on the dipstick, I use the following technique. Check the fluid when the light is good. Read both sides of the dipstick - front and back. Check it three times. When you get consistent readings front & back two times in a row - that's the true level.

Second thought. Some models have a gizmo which softens the shifting of the transmission until the engine reaches a certain temperature. I have seen transmissions immediately gain a cold flare when switched to synthetic fluid. The solution is to disconnect this "shift softener" device. It's as simple as unplugging the electrical connector from a switchover valve. Don't know whether your E420 has such a thing, but if so you might want to disconnect it. You'll have to search the electrical/vacuum diagrams for your car to find out if it exists. What brand of transmission fluid are you running?

- JimY

Well, I'm hopefully at the end of my tranny problems - I pick up my car with a rebuilt tranny in a couple of hours. :)

I had a similar problem that you are describing, and can tell you that by adding some Lucas, and then changing to RedLine synthetic ATF, I was able to see some improvements - and I was able to drive the car (with it getting progessively, but slowly, worse) for over 15,000 miles before it actually starting "slipping" in gears (at which point I was afraid it might leave me somewhere, so I had it rebuilt...)

For the record - you can find places that will rebuild these units (or exchange your damage unit for one of their rebuilt) for about $1300. I got real lucky (I hope) and found a reputable garage (that does tranny's only) and they did it for $1200 (complete, including R&I tranny in car).

-David

Wow. I actually "provoked" a response from the readership? ;-) Seriously, thank you for responding!

Regarding the fluid level, I am 99% confident in the method used -- checking it on a level surface with coolant temperature at 80 *C, reading the correct level marking on the dipstick, and doing so at least three times.

What you described is a computer-controlled shift delay until the coolant temperature reaches 60 *C (?). My vehicle has that by default in the stock program, but it's removed in the chip currently installed. The shifts would actually flare under load well after reaching operating temperature as well. Shift problems existed well before installing the aftermarket ECU, for the record.

With 500ml extra fluid, the condition no longer exists in either operating scenario.

I typically use Valvoline dino fluid, most recently switched to the "high-mileage" blend. From what I can tell, this formula maintains viscosity at lower temperatures without relying on synthetic additives. I will probably change the fluid and filter again within the next 5000 miles, and not worry until clutches start slipping again.

-DM

DaveL, good luck with the rebuilt transmission! I have yet to approach a local transmission shop for a quote, but can tell from this forum that rebuild price ranges all over the map. I hope the fluid level gremlin can extend the transmission life at least another year.

-DM

Synthetic A.t.f.
 

D.M.,

The question about "What fluid do you use " refered to your choice of A.T.F.!

If You are using a synthetic ; certain allowances are in order.

As did my answer --

http://www.valvoline.com/pages/products/product_detail.asp?product=6

It's nothing more than regular Dex III (i.e. "dino fluid") with an additive to increase viscosity at lower temperatures. Not sure you will find me using the "MaxLife" motor oil though... Mobil has treated my cars just fine for years.

-DM