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6 speed manual upgrade

Lacelle

Lacelle

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I am looking to upgrade my manual 4 gear to manual 6 gear on my 1969 K5 blazer.
Has anyone done this ?
I have a SBC 350 in the truck and original trans and transfer. Axles have been changed to 3/4ton 8 bolt. Disc brake.
My research is leading me to the T-56 or TR6060
Which should bolt up !?
Any feed back on this before I get started would be greatly appreciated.
Thanks
 
All of those transmissions start out as 2WD, so there is one hurdle there.

Aside from that, 1st gear on a T56 is super tall. 1st gear in a T56 is closer to 3rd gear in your current trans than it is to 2nd.
 
I don't think a t56 or tr6060 was ever offered in a 4WD application, I believe that ZF6 or a NV5600 would be better options, but you'd have to hope for more folks to chime in if you want any more info, that's all I got...
 
I agree, I don’t think those trans were offer in 4wd applications so they’d never be strong enough to last even if you figured out a way to adapt one.

As for the trucks transmissions, I’ve never seen a ZF6 but I know the NV5600 and G56 (like my Dodge) are HUGE. I’d bet you could see half of it hanging below a stock floor pan.
 
All the 6 speeds are gigantic. There is a reason almost nobody does a 6 speed swap in these trucks. Even the 5 speed swap (NV4500) isn't tremendously more driveable other than offering an overdrive. Expensive, somewhat fragile compared to the SM465, very specific fluid needed.
 
nvrenuf said:
As for the trucks transmissions, I’ve never seen a ZF6 but I know the NV5600 and G56 (like my Dodge) are HUGE. I’d bet you could see half of it hanging below a stock floor pan.
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I too like to shift unnecessarily often.

A car trans seems to be what you're looking for but the ratios may not do well in a full-size truck.

Nv4500 is a nice in between. And a cakewalk swap.
 
ZF6 fits in these trucks. Its no taller than an NV4500, but it would hang down an inch or two lower. They drive like car transmissions, especially with a short throw kit, and are pretty dang stout. You'd need to make a Frankenstein clutch, flywheel and pressure plate assembly to mate it up to a small block though. You'd probably need to get a custom machined bushing for the back of the crank as well. The ZF6 input shaft is much larger than an NV4500 or SM465. Bellhousing bolt pattern is the same as the older transmissions. It runs a 29 spline output shaft with a standard 6 bolt round t-case adapter. You'd need to put a 29 spline input shaft from a ZF or Allison equipped duramax or 8.1L big block truck into an NP241 if you want to run a flanged front output. This requires some minor machining on the front bearing surface or a spacer to set the gears into the planetary ring gear properly.
 
Anything can be done with enough time and money, but the reasons noted above are why you don't see it frequently. Too much hassle and cost for minimal advantages, and you have some choice in 5 speed transmissions. You can run a later model NV3500 which shifts nicely and will be fine for light duty, or you can use an NV4500 which doesn't really address the wide ratio gaps of the SM465 but it's strong and has an overdrive. Both of these transmissions go in a lot easier than any of the 6 speeds.
 
Russell said:
ZF6 fits in these trucks. Its no taller than an NV4500, but it would hang down an inch or two lower. They drive like car transmissions, especially with a short throw kit, and are pretty dang stout. You'd need to make a Frankenstein clutch, flywheel and pressure plate assembly to mate it up to a small block though. You'd probably need to get a custom machined bushing for the back of the crank as well. The ZF6 input shaft is much larger than an NV4500 or SM465. Bellhousing bolt pattern is the same as the older transmissions. It runs a 29 spline output shaft with a standard 6 bolt round t-case adapter. You'd need to put a 29 spline input shaft from a ZF or Allison equipped duramax or 8.1L big block truck into an NP241 if you want to run a flanged front output. This requires some minor machining on the front bearing surface or a spacer to set the gears into the planetary ring gear properly.
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Is that the same 29-spline as the Dodge 29-spline ?
 
Thank you for all the info guys, I'm gonna wait it out for a deal on a 5 or 6 speed trans. After researching the cost on these options i don't know I'll save enough with the Hyw gears to justify the project at new value. i am setting this truck up as my daily driver and just want some Hyw gears but at the same time don't want to loss my pulling gear as I need to be able to pull my boat out of the water.
Thanks for all the great info,
 
Lacelle said:
Thank you for all the info guys, I'm gonna wait it out for a deal on a 5 or 6 speed trans. After researching the cost on these options i don't know I'll save enough with the Hyw gears to justify the project at new value. i am setting this truck up as my daily driver and just want some Hyw gears but at the same time don't want to loss my pulling gear as I need to be able to pull my boat out of the water.
Thanks for all the great info,
Click to expand...


Can always use low range for pulling the boat out of the water .
 
I don't see your gear ratio and tire size.

As mentioned, 4lo, hubs unlocked, is excellent for backing up a trailer, and being able to pull things without spinning the tires. The NP241 t-case has a good low range (2.72) so much better than a 205 if you have that. Just an idea.

If your gears and tires don't have the engine screaming at 65MPH, and you don't plan on driving tens of thousands of miles, I don't think I'd worry about the NV4500. You'll find it very hard to use cost savings to justify modifications to these rigs.
 
The overdrive gears in the car 6 speeds really reward deep axle gears. Like really deep. 6.17s and 35s deep if you get the 50% over version. That makes the shallow 1st gear more usable but you have to factor a gear swap that may not even be possible into the whole deal.
 
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