[Cruiser Jimmy]

Well an end result has come sooner than later. The transmission I rebuilt finally sh*t the bed. In mid to late August while driving down the interstate, the transmission over heated bad enough to start leaking ATF out the from main tranny seal (basically I boiled off the ATF.) My newly added Autometer gauge I put on about a month earlier told me that the temp was well over 260º (the upper limit of the gage), I bet I reached 300º. So it lasted 8 months and a GSMTR trip, not too bad. My purpose in rebuilding the tranny was educational.

The conditions at which the tranny operated at from rebuild to August were mostly a 22 mile round trip to work and back, some highway driving that lasted about 30 miles on the weekend and two very long trips, one to GMSTR and one to Slade Kentucky for some wheelin with some Bluegrass’ers.

Getting the rig back on the road was not so bad. A while back I remember seeing Lowtideride selling an A440F that he had laying around. So over Labor Day I drove down to FL to pick it up. Thanks again Al.


So what happened?

The cause:
Well, if you read the first thread you should’ve picked up several items I did not replace on the tranny. The springs inside the VB were never replaced. In fact, I was even considering not rebuilding the VB at all when I first did it. But since it was down I thought I might as well, I figure it’s better to be a little educated on the VB then ignorant.
As I reassembled the VB I was tasked with putting the springs and pistons back together. This was not hard because the tranny FSM told me what the spring should look like (Number of Coils: 8.5, Length: 25mm, Color: blue, Diameter: 10mm). Well I measured the overall length on some, not all, and found small variations in the length. I was not too concerned about it so I reassembled.

From then until now I have been casually researching the net and asking transmission specials in the Indy area what could have gone wrong for the tranny to over heat like it did. As a result of not changing out the springs in the VB I did not have enough hydraulic pressure at the Lock-up spring(s).

The effect:
As a result of insufficient lockup hydraulic pressure to the torque converter, the lockup would not fully engage. As a result of insufficient engagement of the lockup, heat was able to build up and slowly started to degrade the clutches and brakes inside the tranny.
One of the best explanations on auto tranny and lock-ups is here:
Torque converter lockup | Motor | Find Articles at BNET.

In my early research, I came to understand that fluid turbulence generates heat just like air molecules above the trailing edge of a fixed wing aircraft. So thinking that turbulence played a role in the impeller and turbine, I started there to understand the thermal dynamics of TC’s. For whatever reason back in high school I did not take physics class, so I headed to a co-worker, a design engineer, to explain my overall situation and to understand a little bit about the basic principals. I asked the question, why would liquid hitting again liquid generate heat. He could not answer that, so I had to go to anything source to find out.

Although heat is a byproduct of turbulence in between the impeller and the turbine this was not the root cause of the problem. My condition for heat was being generated during highway speeds, when the lockup was supposed to be in effect. I wanted to know a little more about TC’s so I decided to cut mine open to see the internals.

Pics and other info:
Below are the guts of an A440F Torque Converter. This is considered to be a middle stall torque converter based on the angle of the impeller fins. The impeller is the rounded portion of the TC. Note the raised fins toward the end were its cut open. A vertical (raised) fin means it’s a middle stall torque converter. An angled (raised) fin means it’s a low stall TC. Stall is the full engagement of the engine and tranny via the TC, or a 1:1 ratio. You can find the stall speed of the tranny by holding the brakes down and fully pressing the skinny pedal. WARNING, don’t do this for more than 5 seconds or you’ll burn up the clutch packs. Once it’s engaged note the RPM’s, this is the stall speed of the tranny.

Enjoy.
Jimmy.

Pic 1: you can see the entire TC.
From Left to right: Back cover (lockup surface), turbine with lockup, one-way clutch stator, impeller.
Pic 2: Impeller fins.
Pic 3: Oneway clutch stator

[Cruiser Jimmy]

pics


1: Turbine. This directs the oil to the impeller to create a force needed to turn.
2: Lockup. This plate actually seperates from the turbine and mates against the cover surface at speeds under 40-55 mph.
At speed over 40-55mph the turbine and lockup and back cover come together as one.
3: Lockup seperated...........................................

[Cruiser Jimmy]

more pics

Pic 1: Back side of lock up damper with lockup plate off.
Pic 2: Lockup plate.................................................. ......................
Pic 3: Cover lockup surface.................................................. ..........

[Cruiser Jimmy]

and more pics

Pic 1,2,3: Turbine.

[Cruiser Jimmy]

and even more pics

This is a reassemble of the TC.

Pic 1: Stator on impeller
Pic 2: Turbine on stator on impeller
Pic 3: Lockup plate on Turbine on stator on impeller.

And not pictured, finally you would have the cover over the lockup.

[Cruiser Jimmy]

Here's an illustration of the impeller fin direction, They're the raised fins around the outer most circumference of the TC.

[IdahoDoug]

JK,

Well, sorry to see that it didn't work out but that was a mighty impressive rebuild effort. So, I take it these pics are the aftermath of the failure?

DougM

[Cruiser Jimmy]

Doug,
Yep, with the TC out I decided to put the grinder to work. The tranny is still sitting in the corner of the garage cooling off.

[alia176]

couple of pics show what is similar to a pressure plate from a manual tranny. Does it behave similarly to a manual tranny?

[RavenTai]

Originally Posted by alia176

couple of pics show what is similar to a pressure plate from a manual tranny. Does it behave similarly to a manual tranny?

that is the lock for the torque converter, it kicks in at highway speed to stop any slip in the TC, improving efficiency and reducing heat in the transmission.

[cruiser larry]

Jim I would say you are not going to have it done for toys for tots.Glad to hear you have another one to put in.

[Cruiser Jimmy]

Ali,
Same concept, force is applied after about 40-55 mpg w/ hydro fluid, like RT stated. I would imagine that the force on the lockup plate/rear cover is similar to a manual trannys preassure plate.

For the 442 and 343 guys, a solenoid is used to send the hydraulic preassure to the lockup which in turns forces the turbine to the cover (and the lockup plate) and sequencually the turbine is connected directly to the drive gear inside the tranny.

The two connection points between the TC and Tranny are:
1. Turbine to the tranny drive gear which is rotating mass.
2. Oil pump to the stator. In these two objects, the oil pump is stationary (bolted to the tranny) and the stator rotates (only in one direction). The stator has a one-way clutch on it which prevents counter rotation. The clutch in the stator is nothing like a clutch say. . like on a manual tranny. The stator uses steel rod in a wedged shaped faction around the circumference to achieve one-way direction.

[lowtideride]

Hows the tranny and t-case holding up? I hope well...

[Cruiser Jimmy]

Holding up good. The temp is a little high. Yesterday it got up to 200 while going to and coming from the Hoedown in Attica, IN but hold steady at 190 while on the road after the cool had time to kick in. 3 Weeks ago it got up to 210, 94 degrees outside. I expect the temp to be back to around 170~180 in the Fall/winter time.

[lowtideride]

Hope it holds strong for you...



How big of a cooler you got on it?

[Cruiser Jimmy]

Hayden's 12"X11". You don't want the tube with the heat fins, it's not as efficient
as the sandwich plates style with heat fins.

Advance Auto Parts, Discount Auto Parts, Autozone should have them on the shelf.

[lowtideride]

Originally Posted by jklubens

Hayden's 12"X11". You don't want the tube with the heat fins, it's not as efficient
as the sandwich plates style with heat fins.

Advance Auto Parts, Discount Auto Parts, Autozone should have them on the shelf.

I have the same haydens on my PS, hydro set up...

[NaterGator]

Sorry to hear about your troubles after all! Impressive effort though, and cool pics.

For those curious, here is a link to the original rebuild thread:
Tranny Rebuild -Shadetree Mechanic Style

[Cattledog]

Thanks for the follow up jklubens.

Do you have any thoughts on shimming the VB springs? The idea would to be to increase the clamping force of the clutch packs and create less slip in shifts due to the higher oil pressure. I have read on a supra site that they suggested this to improve reliablity in high HP/TQ supras.

Any thoughts would be great.

[wildsmith]

Lock up stopped working on mine recently. Electrics check out ok but there was no flow through the cooler. Bypassed the cooler but still no lockup. Changed the valve body for one from Rodney, still no lock up. Waiting for a TC from Rodney now, see if that fixes it. Jury is still out as to wether the cooler failed and killed the TC lock up, or did the TC lock up mechanism fall apart and block the cooler? Don't know if the direction of flow etc makes it possible for a TC to kill the cooler.

It's worth checking you're getting good flow through the cooler if you have any transmission heat problems.

Jon.