Hump vs transmission and other related questions

[65 wonton]

I have a 66 with, I think, a high hump. It can be seen here on post #18.

I am vasilating between a 4l60 transmission (that came attached to the ls1 from my 98 T/A, which I already have), a T56 or a NV 4500.

Hydraulics doesn't scare me. wiring, cabling, speed-o, crossmember issues are all a wash. I know that I can acquire bolt-up transmissions for the LS! in all 3 models (at least the T-56 and 4l60).

One question is:
1. What are the physical size/footprint differences between the 3 transmissions?
2. Will the firewall and floor take any of these without alteration (no issue with the shifter location for me)?


The LS will not likely go above 500 HP intentionally. The original truck was manual 4 speed. The steering column will be changed (tilt) anyway. 2wd. Daily driver.
A. Is there a difference as far as sturdiness of the transmission for the LS1, power wise?

I know that there will be a question of differences in cost, $600-1400 and driving preferences Stick vs manual and am not asking that.

I just haven't seen these transmissions in real life or side by side to have an idea of fit or experience to know function.

Thanks,

Dave, this should be as easy as 4,5,6.

[theastronaut]

I don't know about the automatics, but here is how the 5.3/T56 combo fits in my '66 with a low hump floor and F-body oil pan. It's lower and farther back than most swaps since I wanted better weight placement. You'd have plenty of room with a high hump.







Clearance around the T56.






Header clearance.

[66Submarine]

Those are all very different transmissions. NV4500 is a wide ratio truck trans, T-56 is a close ratio double OD sports car trans. And a 4L60, well, I'm not a fan. It seems like some people are using them with success, though. In stock form they are a POS, IMO.

[gofastnut]

Originally Posted by 66Submarine

... A 4L60, well, I'm not a fan. It seems like some people are using them with success, though. In stock form they are a POS, IMO.

Yep, stock they're just big paperweights.
But, rebuilt they're NICE! Although it's about $1500 just for the rebuild....

[65 wonton]

theastronaut, thanks for the pictures. There does seem to be a lot of room that I never would have expected.

66Submarine and gofastnut, thanks for the reply. See, that's what makes this place. Other sites have raved the 4l60 as the greatest automatic transmission ever built! Maybe it was the manufacturer's site or something.

The only other thing I've heard about the 4l60 is that the ls1 torque rips it off the rear t-mount when romped.

So does the $1500 mean post acquisition?

I have 2 dodge cummins, one with a G-6 and one with a NV 5600. I like them both but assumed that neither would fit without cab modification. What other choices are out there?

[theastronaut]

Originally Posted by 65 wonton

theastronaut, thanks for the pictures. There does seem to be a lot of room that I never would have expected.

Don't forget that that's with the engine dropped down right on the crossmember with about 1/2" clearance to the oil pan. That will make header clearance tight, but I'm planning on building my own headers to solve that. Stock manifolds may clear though. You already have a F-body oil pan to help drop the engine lower. As far back as my engine is, the valve covers are close to the firewall but there is room to remove them. I'm relocating the coil packs so I haven't checked to see if they clear the firewall. A stock T56 is rated at 450 ft/lb and they've been known to hold up to more than that so you should be good there. If you're planning on keeping the bench seat then you'll need a shifter relocation kit from Keisler.