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V-drive overdrive

welldigger00

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Has anyone ever heard of running a Gear Vendors auxiliary overdrive behind their transmission on a vdrive boat before? I don't know if this has been brought up in the past, but I would love to see if it's been done, and the pro's and con's with it.
 

BUSTI

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Don't think it would be needed. You can just increase the OD with the v-drive gears. A turbo 400 will reduce it plenty for take off.
 

welldigger00

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I got a th400 in it now, and 32's. I don't know if it's been done, maybe not successfully? That's why you don't see them? I was thinking it might be cool to have a higher end gear to cruise at lower RPM, but not have a faster docking speed in 1st...
 

BUSTI

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I know someone will correct me if I am wrong but cruising at a lower rpm may not be a good idea. I think you would want to know your engine vacuum at cruise. Engine vacuum may be the best way to determine actual load at cruising rpm.
 

Jed-O

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Has anyone ever heard of running a Gear Vendors auxiliary overdrive behind their transmission on a vdrive boat before? I don't know if this has been brought up in the past, but I would love to see if it's been done, and the pro's and con's with it.
7
I have thought about this too John. My idea was to swap my TH350 with a 700R4. But I wasn't sure if it would give me better mileage at cruising speed 50-60 or just flat out bog the motor down to the point it is hurting the mileage more than it helps. I know our boats are apples to oranges in weight and H.P. and what may work on your blown Schiada might not work on my 425 horse Cougar tunnel.
 

tony

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Alexi from boostpower has changed the third gear in a turbo 400 from 1 to 1 a slight over driven gear I think .85 because he couldn't fit any bigger gear in the V-drive!! It was for his 21 Schiada with 2000+HP......
 

welldigger00

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I know someone will correct me if I am wrong but cruising at a lower rpm may not be a good idea. I think you would want to know your engine vacuum at cruise. Engine vacuum may be the best way to determine actual load at cruising rpm.
I'm not so much worried about vacuum, because I'm gonna be pushing around a 1000 HP with a blown 598.
 

Jed-O

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Interesting thought :thumbsup
 

welldigger00

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Hey Jed-o. I think it would be cool if it could handle the power.When are you gonna get me some numbers on my remodel?
 

Jed-O

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getting ready to call your wife right now :D Finished my ball park numbers this morning
 

Racey

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I don't think a gear vendor would hold up to the sustained load of a marine application where you had enough power to warrant the od, a turbo 400 doesn't have a high "gear" so to speak, high just becomes a straight through clutch lock up, no gear meshes are transferring power in high, I remember Alexi saying he was running an old in his trans but I'm not sure exactly what they've done unless they have re ratioed one of the lower gears to become an OD and 2nd gear takes the roll of 1:1. Maybe he'll chime in and clarify exactly what he has. You are always better off running a 1:1 clutch lock at high HP/tq as it's stronger and doesn't build heat like an additional gear mesh does.

The right way to do this is to put bigger gears in the drive.

Typed this from my phone so excuse the brevity
 

welldigger00

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I agree the correct way to do it is to change gears as well. I was just curious to see if it was a possibility. I had one(gear vendors) in a truck that I had that I used to pull my Fifth wheel. It was pretty tough, but maybe not for 1k hp in a 21 rc....
 

Racey

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I agree the correct way to do it is to change gears as well. I was just curious to see if it was a possibility. I had one(gear vendors) in a truck that I had that I used to pull my Fifth wheel. It was pretty tough, but maybe not for 1k hp in a 21 rc....
Not only that, but in your truck, even towing, you maybe only need 50-100 hp to keep the thing moving down a flat road, and maybe only 100-300 pulling a grade, in a boat 300 hp is your cruising speed, imagine pulling a grade for an hour solid.... the loads and duty cycles are way greater in a boat, with no cool off periods. Not to mention that if you were pulling a heavy grade you'd most likely bypass the overdrive in a truck anyway.
 

alohajeff

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Offroad racers are running underdrives because they can use stronger ring and pinion sets without having to increase ring gear or housing diameter. Call Jayson at Tubeworks and ask him. He might have something "overdrive" related sitting on a shelf you could try. If it holds up to 800hp in a trophy truck it might stand up to marine use.

Aloha
 

welldigger00

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I had another thought. Instead of a th400, how about an Alison? Just thinking outloud here. I think direct is like 4th gear,and there is 2 more overdrives beyond that.
 

BamBam

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I had another thought. Instead of a th400, how about an Alison? Just thinking outloud here. I think direct is like 4th gear,and there is 2 more overdrives beyond that.
Or a GM 4L80/4L85 in full manual (electronics removed) that way you have the strength and basic ratios of a TH400 in 1st to 3rd and then an OD with 4th to cruise with. This idea was tossed around when we put my boat together.
 

welldigger00

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I think it would be cool. Especially on a big lake like Powell or mead, where you are covering 30 miles in one run.
 

Jed-O

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...And not have to worry about fuel stops along the way.
 

BigSteve

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Has anyone ever heard of running a Gear Vendors auxiliary overdrive behind their transmission on a vdrive boat before? I don't know if this has been brought up in the past, but I would love to see if it's been done, and the pro's and con's with it.
We ran a TH 400 trans in a boat before worked great at the docks and pulling skiers.

I think the cons win ! Don't see any pro's to running a overdrive on a TH 400

I would talk with the K-69 team. They had a # of custom props for the Kilo record.

The correct prop and gear selection for your power can be found with some testing
 

welldigger00

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We ran a TH 400 trans in a boat before worked great at the docks and pulling skiers.

I think the cons win ! Don't see any pro's to running a overdrive on a TH 400

I would talk with the K-69 team. They had a # of custom props for the Kilo record.

The correct prop and gear selection for your power can be found with some testing
It seams that the consensus is that it's not feasible. Thanks for everyone's input, it has been enlightening.
 

025

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Offroad racers are running underdrives because they can use stronger ring and pinion sets without having to increase ring gear or housing diameter. Call Jayson at Tubeworks and ask him. He might have something "overdrive" related sitting on a shelf you could try. If it holds up to 800hp in a trophy truck it might stand up to marine use.

Aloha

Jason and I talked about this last week (they use 5 planets, I think gear vendor is 3) for the 28' speedster project. It's basically an under drive turned around. 1000hp shouldn't be a problem. Even a couple thousand hp. They hooked a stress gauge to the drive train of a TT and the stresses were off the chart in whoop sections. Acceleration when the tire had to "climb" the whoop when running through them. Exact numbers slip my mind. Down side is
1. It's $8k
2. It's not shiftable, so gears might as well be the same. For $300

I don't think the gear vendor will take the sustained power and really don't think it'll like a full throttle up shift.

Basically a geared right set up will pin you in the seat with a 3 blade to 90 +\~. Faster and a 2 blade, just have to roll into it more.

Save your money for the mufflers:)
 

welldigger00

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Actually, I am thinking a whole new direction now. I'm thinking about a fan boat like the ones in Florida. With a variable pitch prop. The upside is I don't have to wait for anyone at the launch ramp. I'll just launch in the parking lot and haul ass down the ramp like the marines would do it. Or better yet, I'll just launch from home and run it down the highway! With a 1000 horse, and some casters, or maybe Teflon on the bottom, I should be able to get it done.
 

welldigger00

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Jason and I talked about this last week (they use 5 planets, I think gear vendor is 3) for the 28' speedster project. It's basically an under drive turned around. 1000hp shouldn't be a problem. Even a couple thousand hp. They hooked a stress gauge to the drive train of a TT and the stresses were off the chart in whoop sections. Acceleration when the tire had to "climb" the whoop when running through them. Exact numbers slip my mind. Down side is
1. It's $8k
2. It's not shiftable, so gears might as well be the same. For $300

I don't think the gear vendor will take the sustained power and really don't think it'll like a full throttle up shift.

Basically a geared right set up will pin you in the seat with a 3 blade to 90 +\~. Faster and a 2 blade, just have to roll into it more.

Save your money for the mufflers:)
You still haven't given me a price for the mufflers yet. Better do it soon before I run out of money!
 

Jed-O

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Actually, I am thinking a whole new direction now. I'm thinking about a fan boat like the ones in Florida. With a variable pitch prop. The upside is I don't have to wait for anyone at the launch ramp. I'll just launch in the parking lot and haul ass down the ramp like the marines would do it. Or better yet, I'll just launch from home and run it down the highway! With a 1000 horse, and some casters, or maybe Teflon on the bottom, I should be able to get it done.
Yeah Air Boat! :beer
 

BoostPower

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Alexi from boostpower has changed the third gear in a turbo 400 from 1 to 1 a slight over driven gear I think .85 because he couldn't fit any bigger gear in the V-drive!! It was for his 21 Schiada with 2000+HP......
Yes. Mine equates to a total ratio of 84.94 62's in the box .74 overdrive with a 12 x 16 1/8. I like it🏻
 

AzGeo

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Were the T-400 parts from John Killgore ?
 

BoostPower

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No mine are a few custom parts and a few other basterd 4l80 parts and some misc. Today I would just do a 4l80 custom build with ecu control and lock up
 

BamBam

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No mine are a few custom parts and a few other basterd 4l80 parts and some misc. Today I would just do a 4l80 custom build with ecu control and lock up
I like the idea of the 4L80 beefed up. I'm not sure I would want it for top speed runs but to knock the RPM down while at cruising speed. Please explain how you would use the ECU control and Lock-up. I understood that lock-up in these transmissions had to do with the torque converter and we don't use torque converters in the boats so I don't know what you would lock-up. Let me know so I can learn.

Thanks
 

BoostPower

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I like the idea of the 4L80 beefed up. I'm not sure I would want it for top speed runs but to knock the RPM down while at cruising speed. Please explain how you would use the ECU control and Lock-up. I understood that lock-up in these transmissions had to do with the torque converter and we don't use torque converters in the boats so I don't know what you would lock-up. Let me know so I can learn.

Thanks
Mine is not a 4l80 but we do use a special made converter for the boats that have a 2 pitch lock up. Ecu can control the pressures and shift points if you were to use a full auto setup.
 

vdcruiser

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Whats involved in changing the second gear ratio in a turbo 400 to a higher gear,(lower number), so it would work better on take off? I can use it now, but it will over rev quickly if you stand on it. My boat is a 21 Howard with a blown 548 and 48% gears in the V drive.
 

BamBam

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Whats involved in changing the second gear ratio in a turbo 400 to a higher gear,(lower number), so it would work better on take off? I can use it now, but it will over rev quickly if you stand on it. My boat is a 21 Howard with a blown 548 and 48% gears in the V drive.
I don't think you'll ever make 2nd so tall that it doesn't hit the rev limiter with a blown 548. You just need to short shift that thing, or start in 3rd.
 

BoostPower

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Whats involved in changing the second gear ratio in a turbo 400 to a higher gear,(lower number), so it would work better on take off? I can use it now, but it will over rev quickly if you stand on it. My boat is a 21 Howard with a blown 548 and 48% gears in the V drive.
They make higher first n second planetary sets! It works good
 

AzGeo

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He was in Burbank Calif. when I did business with him over 15 years ago . He had a .32 second gear VS the factory .48 . It is perfect for 32% + gears in the V-drive . It's also nice if you have taller gears in the V-drive for pulling skiers in second at lower speeds, but at good oil pump RPMs .

He also has a couple of 'super low' first gear sets for T-400, perfect for a 'boat tow-r' that has 3.50/3.70 rear end gears .

The old factory GM 'Dual Range Hydramatics', had a 'switch pitch stator' in their converters . The front pump housing has an electric/magnetic system in it, like a compressor clutch . The converters were available in 1600/2600 and 1800/2800 RPMs . We would use these in our cars/trucks back in the 1970's, for towing and 'jump off the line' .

I would not use a converter in a boat, the prop is where the 'cushion and slip' are .
 

BoostPower

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He was in Burbank Calif. when I did business with him over 15 years ago . He had a .32 second gear VS the factory .48 . It is perfect for 32% + gears in the V-drive . It's also nice if you have taller gears in the V-drive for pulling skiers in second at lower speeds, but at good oil pump RPMs .

He also has a couple of 'super low' first gear sets for T-400, perfect for a 'boat tow-r' that has 3.50/3.70 rear end gears .

The old factory GM 'Dual Range Hydramatics', had a 'switch pitch stator' in their converters . The front pump housing has an electric/magnetic system in it, like a compressor clutch . The converters were available in 1600/2600 and 1800/2800 RPMs . We would use these in our cars/trucks back in the 1970's, for towing and 'jump off the line' .

I would not use a converter in a boat, the prop is where the 'cushion and slip' are .
Converters are almost never used! In an ultra custom deal with super high gears they can be setup custom to lock up 1-1 and have a slight slip with 2 ranges depending on drivability needs. 🏻
 

AzGeo

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I just like them 'simple and clean', which usually equals low maintenance . Built a couple with an 'automotive clutch', just to make them more manageable around docks . Considered a 'Brinn 2 speed" (circle track car trans) with it's own built in clutch system, but don't know if it will hold all the torque without slipping .
 
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