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T56 Transmission Swap


PittySS
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I was wondering if anyone has done a T56 swap with 2wd in their SS? All I know about this swap is it will need a custom driveshaft, bellhousing, the gearshift is 6-8" furter back than the NV3500's, and obviously that it only works with 2wd, and that it should bolt in! I know its a big project but i cant resist a 6speed manual.

I also have a RCSB 2004 Silverado 5speed (nv3500) 4x4 with a 4.8L. Will the T56 work with all the same components (clutch pedals, cables, brake booster, etc.) as the NV3500 uses? If anyone has any info or tricks/hints let me know!

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will (boosted silverado) has done it in his rcsb. its definitely possible. you have to take into consideration the weight difference in our trucks vs corvettes. it does play a role in the clutch and transmission longevity

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KellyPerformance did this but the clutches kept breaking I belive

 

will (boosted silverado) has done it in his rcsb. its definitely possible. you have to take into consideration the weight difference in our trucks vs corvettes. it does play a role in the clutch and transmission longevity

^^This.. I was considering it myself. In an RCSB, such as Will's truck, I see it as a reasonable option. But in a full size pickup, HP/Weight makes clutches a maintenance item. John and others that have done this swap, but have converted back to a 65/80e not even 2 years later. They got tired of doing a clutch job every summer. Lol. But yes. The T56 can take abuse, but these trucks just weigh too much IMO. But if its what you really want, go for it. Just don't cheap out on the clutch when you're buying parts..

Again. Not saying it cant be done. Just others haven't had much luck.

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Ya the weight would be harder on clutches, but it should take it. My 04 RCSB 4x4 has the nv3500 5speed with 260,000km still has original clutch! Release bearing is getting tired tho. So i guess an nv3500 (1500) or nv4500 (2500hd) 5speed would be a possibility aswell, but its not a T56....

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iv put a t56 in a reg cab. I can tell you that all the NV3500 stuff is all compatible. atleast hydaulic wise. You will need to use a f body clutch and throwout but crossmember will work. BUT these trucks are very very heavy and the t56 is not meant to throw around that kind of weight. It will eat threw clutches as well. the sheer weight of the truck is destructive.

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yes I did do this, and the transmission is not the issue. we have since done this in a RCSB, and it worked fine. my heavy ass SS that was pushing about 570-580 whp at the time on 3.73 gears was eating up clutches. however, if I would have thrown a ZR1 twin disc with a Katech or LPE 6 bolt flywheel, and swapped my gearing to 4.10 or 4.56, it would've been okay. I used the absolute PERFECT transmission, but it was freeking impossible to find when I did this first, back in like 2006 or 2007. it was the T56 out of an 05-06 Chevy SSR LS2. they were beefed up to hell, even heavier duty than the viper units. a t56 magnum would suffice just fine though. I wouldn't do a tr6060 tho, the earlier ones had lots of issues, and I prefer the T56 for other reasons anyways.

 

so to sum it up here is what you will need- unless you can find an 05-06 SSR T56, you will need a 98-02 F-Body T56. this will bolt up to your motor, with any LS1 clutch. USE either a very heavy single disc, which is miserable to drive... or a nice twin disc. honestly we find the ZR1/LPE twin disc works great, and the pedal is light and forgiving. they hold up to 900 whp that ive personally seen, zero issues (this is in a car! truck is way heavier, so cut a few hundred lb.ft off that).

-F Body T56

-HEAVY DUTY single disc/twin disc clutch setup for LS1 F Body

-LS1 slave cylinder from an F Body

-Clutch pedal and master cylinder (comes together) for a 5 speed GMT800 truck (99-07)

-2.5" hole saw

-plasma cutter or die grinder (to make that fairly large hole in your floor :lol::banghead: )

-there is actually a bracket for the clutch pedal under your dash: you simply need to rivet some rivet nuts into the two holes. the pedal assembly will then bolt in.

-master cyl twists into the pedal assembly that comes through the firewall, right under your TAC module. (there is an outline of a circle on the firewall where you will need to dril the 2.5" hole for the pedal. punch it perfectly in the center, pilot hole and drill it.)

-hook up the slave and master, already bled if you buy them new.

-buy a 5 speed trans crossmember, or modify your automatic one

-you will need to custom make shifter linkage to your desired location: mine was in the OE console next to cup holders

-if you have a 1 pc. driveshaft, it will most likely need to be modified. the 2 pc. will work with the T56

-you will need a PCM tune, the truck will not start. if you have a late 2005 or 2006-2007, you have to bypass the "auto cranking" feature or the truck wont crank. this requires soldering a wire from a leg on the starter relay and running it into a pin in the pcm (don't recall pin location)

-for a temporary solution you can leave the "black box" that is on the side of the 4L65, where the shift linkage hooks up. you will need to put it in neutral and keep it plugged in. only issue here is, yes the truck will crank, but it WILL STAY in idle spark tables. also, the fuel level sender for the fuel gauge uses a different algorithm for Park/Neutral and for Drive. your fuel gauge will be bouncing around like crazy.

 

so, is it possible? yes. would I recommend you do it to an SSS? not really. I dumped a nearly unlimited amount of money into the project and it was still a pain in the ass for a DD. now if it was a RCSB, go for it. they are fun as shit. but now that you know whats involved, hopefully it will help educate you on just whats all involved :)

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  • 2 weeks later...

Ya i've read a couple write-ups on the swap, lots of work i know! I have a 2004 so I don't have the blackbox :D but didnt realize the extra weight of an extended cab would pose such an issue with a 6speed.... Maybe this project should wait for a RCSB build one day. Thanks for the great info!

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