Cruiser Jimmy
Moderator
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
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
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