Looking for transmission knowledge

[TWKundrat]

I'm fairly early in a GMC inline 6 powered XO lakester build for El Mirage and Bonneville and I'm just looking for some advice on my transmission selection. It's not exactly my area of expertise. Right now we're thinking about running a modern 6 speed auto like a 6R80 or 6L80 with a stand alone controller. I don't know how much HP we'll be able to coax out of the old inline so it seems like a 6 speed could be helpful to keep it in the power band. Does the 6R80 or 6L80 sound like a reasonable choice for what we're looking to do? If so, is there any particular models that would be better suited (car vs. truck, etc.) or any upgrades we should be doing? Thanks in advance for any advice. I appreciate any knowledge that people are willing to share

[Seldom Seen Slim]

Here's one way to "keep it in the power band":  Run 75% and and you'll have lotsa torque and need fewer gears.

At least - - - 'til you drive over the crankshaft at the 4.  But that's another story.

[Stan Back]

Whatever you choose, try for a set-up where the top two gears are the closest together.

And I'm so old-fashioned I believe that a manual uses less HP than an automatic.  And straight thru on top gear uses less horsepower than a manual with an overdrive.

[floydjer]

***Disclaimer*** I do not have a clue as to what I say..But, The top 2 gears in that trans are overdrive ratios. You might want a 1:1 final drive.

[jdincau]

Send member "jimmy six" a PM. He runs a GMC in gas and fuel roadster classes.

[TWKundrat]

A manual was the original idea but it's a mid-engine, driver up front configuration so building a shifter linkage seems like it would be a challenge.
Does a six speed vs. four really make much of a difference in this type of application? My only land speed racing experience is as a spectator so I'm very appreciative of any advice.

[TWKundrat]

Send member "jimmy six" a PM. He runs a GMC in gas and fuel roadster classes.

Thanks, I'll have to contact him

[TWKundrat]

***Disclaimer*** I do not have a clue as to what I say..But, The top 2 gears in that trans are overdrive ratios. You might want a 1:1 final drive.

Good to know. Thanks

[Stan Back]

My comments don't have a clue about GMCs.  It's just that as you get going faster and faster it takes more HP.  And if you're over the peak in the next to last gear and need to upshift to go faster, you don't want to fall far behind that peak as you may never get there again.

Jimmy, Chevy, Harley -- they're all the same.

[TWKundrat]

Makes sense. Are there any upgrades that you all would recommend to a modern auto trans, or would a stock low mileage one likely suit out purposes?

[Stan Back]

I don't have a clue about automatics -- but I'm sure there are folks here that might chime in.

But with a standard -- with no other gears involved and the power going straight thru makes the most sense (to me) -- you're getting the most HP available when you need it.

[TWKundrat]

I don't have a clue about automatics -- but I'm sure there are folks here that might chime in.

But with a standard -- with no other gears involved and the power going straight thru makes the most sense (to me) -- you're getting the most HP available when you need it.

Yeah I definitely get that. My biggest concern would be making a reliable shift linkage to reach the transmission 6 or 7 feet away from the shifter with a mid-engine setup

[johnneilson]

Use cables, controlcables.com

I use a cable on a mid engine lakester, not cheap, just too easy.

John

[TWKundrat]

Use cables, controlcables.com

I use a cable on a mid engine lakester, not cheap, just too easy.

John

What kind of transmission are you running?

[johnneilson]

2 speed manual
not an automatic