Fmx - Torque Convertor
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From: Longwood, fl
Fmx - Torque Convertor
Have a 55 F100 with a slightly warmed over 351C and a FMX tranny. Don't know what the torque convertor is that is in it but am being told I should change for something in the 2000rpm range for better ride/performance. Am looking at a DACCO model no. PP0612LS that ranges 2000 to 2300 rpm for 289$ to the door. Don't know what spline it is until I get the old one out. Also am planning to add a Lokar floor shifter while I got er broke loose. Anything unusual to be expected for that install as well. Thanks in advance for your input...
Fleet Owner
Joined: Jul 2004
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From: NM
Your stock converter (depending what year it's out of) should have a stall speed of 1800 - 2000. Late 70's were a little lower I think because of trying to "lock up" for better mpg. Why exactly is this being recommended? Is your t.c. just plain bad? It's not a stunning amount of difference, is my point. I'd check the stock specs before making that much of an investment. If you are doing this for performance, I am not sure the difference would be noticeable.
PS -- besides spline count, check ring gear tooth count, converter bolt circle diameter, and pilot (nose) diameter. Last time I bought a C-4 converter, there were 20+ different stock choices!
PS -- besides spline count, check ring gear tooth count, converter bolt circle diameter, and pilot (nose) diameter. Last time I bought a C-4 converter, there were 20+ different stock choices!
Last edited by ALBUQ F-1; Aug 28, 2006 at 01:08 PM.
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From: Longwood, fl
Both the engine and tranny guys have recommended replacing the tc since the idle drops significantly when you put it in gear they believe the tc installed has a to low stall speed. What is the general reputation of the FMX tranny? Thanks for the tips on the spline count, etc.
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Joined: Jun 2004
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From: Riverside, So Cal
Joe -
I run a warmed up 351C with an FMX and stock converter in my 56.
The FMX tranny is very reliable, plenty strong enough for our engines and sucks less power than a C6. My idle in neutral is around 1000 rpm and in gear drops to around 700 rpm. Sound about the same as yours? My converter was new about 17,000 miles ago.
I wouldn't change it. If it was good enough for Henry, it's good enough for me.
P.S.: If you changed the Torque Converter based on those guys' recommendations and it didn't fix the problem, what would they say? Rebuild the tranny?
I run a warmed up 351C with an FMX and stock converter in my 56.
The FMX tranny is very reliable, plenty strong enough for our engines and sucks less power than a C6. My idle in neutral is around 1000 rpm and in gear drops to around 700 rpm. Sound about the same as yours? My converter was new about 17,000 miles ago.
I wouldn't change it. If it was good enough for Henry, it's good enough for me.
P.S.: If you changed the Torque Converter based on those guys' recommendations and it didn't fix the problem, what would they say? Rebuild the tranny?
Roast em' if you got 'em
Joined: Mar 2005
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From: Rio Rancho, NM
Randy brings up a very good point. Despite how much we complain, the factory engineers are a sharp bunch and knew what they were doing.
How much of a difference is there between neutral idle and in gear idle? Maybe its just a tuning issue.
I'd definately opt for a 2nd (3rd, 4th.....etc) opinion.
Bobby
How much of a difference is there between neutral idle and in gear idle? Maybe its just a tuning issue.
I'd definately opt for a 2nd (3rd, 4th.....etc) opinion.
Bobby
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From: Longwood, fl
Thanks for the feedback as usual. When shifting from park into gear she goes from about 1500rpm to 700 to 800 rpm. Also, when she shifts from first to second which is almost instantly when she rolls I get a hesitation almost as if losing power for a second, then everything is fine. Have just replaced the distributor with a new stock dist. Have gone through and added all new performance parts, plugs, wires, 670 holley, headers, etc. Can't seem to get rid of the hesitation when she shifts into second. Also changed the rear end to 3.00 gearing. Also are there any tricks to adding a Lokar floor shifter on the FMX tranny? BTW the engine is supposedly out of a 71 Gran Torino.
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From: NM
Originally Posted by Randy Jack
Joe -
P.S.: If you changed the Torque Converter based on those guys' recommendations and it didn't fix the problem, what would they say? Rebuild the tranny?
P.S.: If you changed the Torque Converter based on those guys' recommendations and it didn't fix the problem, what would they say? Rebuild the tranny?
That's ridiculous, if you ask me. There are dozens of things that could be causing this problem. First off, why is it idling in neutral at 1500?? That's way too high, unless you've got a big cam in it. What is the initial timing set at? Sounds like it could be too advanced, but it also sounds like you've done a lot of tuning on it. I can see why they are suspecting the t.c. but have they done a stall test? That would say definitively if that is the problem. Honestly, I'd be suspicious of the carb jetting, sounds like the idle/low speed circuits are too lean, causing the throttle plates to be open too far to maintain idle in Drive which gives you a high idle in Park. The early shift to 2nd is a linkage or vacuum modulator problem.
These guys could very well be right, but I'm not hearing the evidence right now. Keep in mind a high-stall t.c. is going to flush your fuel economy.
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Roast em' if you got 'em
Joined: Mar 2005
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From: Rio Rancho, NM
I must agree, I think it sounds like a tuning issue. It kinda sounds like a vacuum leak to me. A vacuum leak will also give you a high idle.
Can you adjust the idle down below 1500 RPM or do you have to set it at 1500 RPM so that it doesn't stall when you put in in gear?
A lean condition as Ross explained could also be the culprit. What is the condition of the fuel filter? new? plugged? don't know? how is the fuel pump? good pressure?
If the engine is not getting enough fuel it will also cause a lean condition that can effect transmission shifting as you describe.
Hope this helps
Bobby
Can you adjust the idle down below 1500 RPM or do you have to set it at 1500 RPM so that it doesn't stall when you put in in gear?
A lean condition as Ross explained could also be the culprit. What is the condition of the fuel filter? new? plugged? don't know? how is the fuel pump? good pressure?
If the engine is not getting enough fuel it will also cause a lean condition that can effect transmission shifting as you describe.
Hope this helps
Bobby
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From: Longwood, fl
Will do a stall test Thursday night to check the tc and in the meantime order a new vacuum mod to replace the old one. The truck has been doing the same thing since I bought it and all the new parts have had no effect on the second gear studder. I am running a cam but don't know what it is, already installed by previous owner.
Fleet Owner
Joined: Jul 2004
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From: NM
Bobby's nailed it, I'd bet! A leak would cause the vacuum modulator to be ineffective and result in instantaneous shift to 2nd.
I'm afraid that if you ask a transmission guy why your truck isn't performing right, the answer is always going to be something he can fix!
I'm afraid that if you ask a transmission guy why your truck isn't performing right, the answer is always going to be something he can fix!
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From: Longwood, fl
I owe you guys a cold beer. The vacuum modulator did the trick and she drives like a different truck. Didn't even bother with the torque converter. Best 13 dollars I have spent so far. Tweaked the chocke, fast idle and timing and she runs great.Will proceed to add a Lokar 23" Nostalgia floor shifter. Then onto tire and wheels. But for today she shifts great and is much more fun to drive. Thanks
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From: Lancaster CA
I installed a 12" shifter in my 50. It worked great. The hardest thing was to drop the pan and switch out the tranny levers they give you. Just take your time and if I remember follow the directions. I never had any problems with my fmx.