Lockup torque converter ?
Team Owner
Joined: Jan 2006
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From: Crossville TN
You would be much better off swapping a 700R4 (or 200-4R) overdrive transmission with lockup capabilities for the THM-400. Lockup benefits are not going to come close to cancelling out the 400's inefficiencies.
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From: New Or-leens Loo-z-anna
Team Owner
Joined: Jan 2006
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From: Crossville TN
I am unaware of any 'add on' kit that would provide THM-400 with lockup capabilities. You could put a lockup-capable torque converter on it; but how would you power it and what available pressure source would you 'borrow' to get it to apply??
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From: New Or-leens Loo-z-anna
And then there is the bolt-on "Overdrive"--same cost as a new A/T. My piggy bank isn't big enough to purchase either kit.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
Or, remove yours and take it and the O/D unit to a local (and honorable) transmission shop. Ask them to rebuild the O/D trans to the power level you need; also ask them how much they would offer for a good Turbo-400 core transmission that still works. If they will 'deal', tell them you will need to have them set up the T.V. cable on yours after you get it installed. That may be the route for least expense AND least trouble.
In any event, have fun with it!!!
In any event, have fun with it!!!
Safety Car
Joined: Oct 2004
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From: Youngstown Ohio
Team Owner
Joined: Jan 2006
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From: Crossville TN
Considering that the lockup function merely saves some inefficiencies in converter performance which results in less waste heating and 1-3 mpg savings at highway speeds, I'm pretty sure one could not justify spending $1K and a lot of work for that amount of "gain" 
I have no idea what application would save enough expense to justify buying one.?
I have no idea what application would save enough expense to justify buying one.?
Safety Car
Joined: Oct 2004
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From: Youngstown Ohio
Considering that the lockup function merely saves some inefficiencies in converter performance which results in less waste heating and 1-3 mpg savings at highway speeds, I'm pretty sure one could not justify spending $1K and a lot of work for that amount of "gain" I have no idea what application would save enough expense to justify buying one.?
I have no idea what application would save enough expense to justify buying one.?
Team Owner
Joined: Jan 2006
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From: Crossville TN
Hmmm..... Lockup would give you a direct-drive and bypass the converter, altogether. But, that would also eliminate torque multiplication advantage of the converter.
But, if that is the purpose for the Coan lockup device, so be it.
But, if that is the purpose for the Coan lockup device, so be it.
Safety Car
Joined: Oct 2004
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From: Youngstown Ohio
Lockup doesn't bypass the converter. It eliminates the slip only at top end where no torque multiplication is used. The kit allows you to install a lockup converter, not bypass it.
Last edited by C3 Stroker; Sep 13, 2021 at 03:14 PM.
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
I'll keep my 9" convertor and save probably 20 maybe 30 pounds of rotating weight and the power loss to drive it.
I'm sure they perceive a benefit for some obscure application but I'm not seeing it. Fuel mileage improvement? Not sure I buy that either maybe a couple.
I'm sure they perceive a benefit for some obscure application but I'm not seeing it. Fuel mileage improvement? Not sure I buy that either maybe a couple.
Safety Car
Joined: Oct 2004
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From: Youngstown Ohio
I have a 9" converter also. A good one will multiply torque quite a ways down a 1/4 mile dragstrip with good top end efficiency. I've read some tests where the conventional ones were quicker on the drag strip than lockups.
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From: New Or-leens Loo-z-anna
Team Owner
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From: Crossville TN
Lockup provides a direct connection between the converter pump and turbine, which in my world "bypasses the converter". The converter is a fluid connection between pump and turbine; lockup 'bypasses' that action.
Safety Car
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From: Youngstown Ohio
I know what a converter is and what a lockup does, but lockup doesn't occur from idle. It occurs near top end or a specific RPM point. The converter works normally until that point. That top end point is the only place any bypass/lockup occurs, making the converter 100% efficient rather than the usual 94% or so. Generally, your lockup doesn't even work below 40 mph or so. Some racers like the 100% at top end vs. 6% slippage.