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You guys know that the splines on the mainshaft for 5th gear on the nv4500 only go halfway through the gear, right? What are you going to do when that strips out? Torque King doesn't make their fully splined mainshaft anymore. My truck's been sitting half the summer thanks to the nv4500.
 

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Discussion Starter #22
You guys know that the splines on the mainshaft for 5th gear on the nv4500 only go halfway through the gear, right? What are you going to do when that strips out? Torque King doesn't make their fully splined mainshaft anymore. My truck's been sitting half the summer thanks to the nv4500.
I am fairly new to nv4500s. Driven trucks with them but not swapped one yet. Soon to be swapping 2 . My wagoneer and my 86 Chevy.
What is the cause for 5th gear issues? Towing in 5th? Hard acceleration?
I have heard of fixes but haven’t researched
 

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Ed, hadn't really studied those transmissions but did they correct the problem with the NV5600. I know it is a completely different transmission than the NV4500.
 

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I am fairly new to nv4500s. Driven trucks with them but not swapped one yet. Soon to be swapping 2 . My wagoneer and my 86 Chevy.
What is the cause for 5th gear issues? Towing in 5th? Hard acceleration?
I have heard of fixes but haven’t researched
It's just bad engineering, and there is no fix other than replacing the mainshaft with a fully splined one. Mine failed driving on a gravel work to work, nothing in the bed, not towing or anything. I've only towed once or twice with my pickup since I swapped it in, and never anything heavier than a trailer with a jeep on it. Cummins turned up a little, but still on the stock clutch. I'm looking for a zf6 s650 or s750. The zf 6 speeds are supposedly the best manual ever put in a pickup. GVWR of 26 or 30k. The nv4500's gvwr is half that.
 

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If you're thinking about one of the ZF6 transmissions then you may need a new adapter plate/clutch setup. Both Ford and GM used the S6-650. Pretty sure Ford was the only one to use the S6-750. The GM S6-650 was used on the 6.6L Duramax and 8.1L gas engine. From what I've read, the 8.1 version might bolt up but you may have to work out the clutch parts.
 

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Standard clutch for a 96 NV4500 GM is 12".

That will handle a pretty decent 12 valve fine. 12" organic should handle around 600 lb/ft if your nice with the pedal. Get side-steppy with it and you need ceramic and a tranny with a bigger input shaft.
The stock 12" clutch in my Dodge 1998 12 valve held fine until I installed the #12 fuel plate. The #12 fuel plate is the mildest off-the-shelf fuel plate available (to my knowledge). It allegedly increases power from 215/440 to 230/605. After I installed it, the stock 12" clutch would slip in 5th gear when the turbo would light. I now run a 13" SouthBend 13125-OK-HD. My truck has 3.54:1 gears and 33" tires.
 

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It interesting that the #12 plate gets you the 230 HP on the 215 HP P7100 but it takes a #6 on the 160 HP or #8 on the 175 HP. I guess it's all in the way the pumps are set up. That near 200 lb ft of torque could sure make a clutch slip.
 

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Every NV4500 mainshaft made since the early 2000's has been for full 5th gear splines. Torque king used to sell really nice shafts and gears that 100% solved the problem, but the current basic mainshaft is full spline wherever you buy it and works fine for most anything guys are going to use one for today.
 

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The stock 12" clutch in my Dodge 1998 12 valve held fine until I installed the #12 fuel plate. The #12 fuel plate is the mildest off-the-shelf fuel plate available (to my knowledge). It allegedly increases power from 215/440 to 230/605. After I installed it, the stock 12" clutch would slip in 5th gear when the turbo would light. I now run a 13" SouthBend 13125-OK-HD. My truck has 3.54:1 gears and 33" tires.
There are a ton of variables. Fuel plates don't mean much of anything quantifiable because of all the settings involved.

That being said, let's suppose you made only 230 HP at the crank. It's really not a stretch that you were making 600 lb/ft or really close to it.

My experience with the GM clutch is it works fine behind a 4BT or 6BT for spirited daily driving and towing, but don't drop the clutch and get stupid with it or expect to put 400 HP through it.
 

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Every NV4500 mainshaft made since the early 2000's has been for full 5th gear splines. Torque king used to sell really nice shafts and gears that 100% solved the problem, but the current basic mainshaft is full spline wherever you buy it and works fine for most anything guys are going to use one for today.
My NV4500 has a full spline shaft. I bought the shaft in 2017 when I converted my truck to 4WD. For added insurance I used one of these. The price has increased $25 since I bought mine.


These only work with a 4WD NV4500.
 

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There are a ton of variables. Fuel plates don't mean much of anything quantifiable because of all the settings involved.

That being said, let's suppose you made only 230 HP at the crank. It's really not a stretch that you were making 600 lb/ft or really close to it.

My experience with the GM clutch is it works fine behind a 4BT or 6BT for spirited daily driving and towing, but don't drop the clutch and get stupid with it or expect to put 400 HP through it.
I believe I said in my post the advertised torque for that fuel plate is 605.

I wasn't trying to discredit your experience with a 12" clutch behind a 4BT or 6BT. I was, in fact, sharing my experience with my stock 12" clutch working fine with my stock 215/440 12 valve. I was also sharing my experience with it not holding with my moderately turned-up 12 valve.

I do agree that it's not just the fuel plate that affects performance. I attached a link to TST Products site showing the published results for the fuel plates they sell. The owner is Mark Chapple, a former Cummins engineer. I had a lengthy discussion with him before deciding on the #12 plate. He also shared with me he was on the team that originally developed the 6BT engine.


 

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Discussion Starter #33
Well this went sideways with getting the sbc adapter and nv4500.

thank you everyone for your time.
I will be starting another post shortly about zf5s!
 
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