LGT-700 Manual Transmission - Holy Grail?

[Roadrage David]

If you say so...

Andrew

Yep i say so !!!.
in europe stuf is differend. no 4 speeds 1 on 1 ratio,s. 6 speeds are the most common today

[andrewb70]

Yep i say so !!!.
in europe stuf is differend. no 4 speeds 1 on 1 ratio,s. 6 speeds are the most common today

Which transmission exactly?

Andrew

[Roadrage David]

Take your pick. there are many more brands

http://www.holinger.com.au/index.php
http://racecarsdirect.com/listing/57...d_gearbox.html
this one sits in ken blocks Mustang https://www.facebook.com/pages/SADEV...532?fref=photo
http://www.saenztransmissioneurope.com/

[andrewb70]

Take your pick. there are many more brands

http://www.holinger.com.au/index.php
http://racecarsdirect.com/listing/57...d_gearbox.html
this one sits in ken blocks Mustang https://www.facebook.com/pages/SADEV...532?fref=photo
http://www.saenztransmissioneurope.com/

Not exactly the same comparison. Those are racing transmissions that are $25K plus. They also use straight cut gears made from unobtanium material.

Apples and Oranges my friend...

Andrew

[Roadrage David]

NOP they are not 25 k and iven if they are. They are very strong OVERDRIVE racing transmissions. one link i put on was a 24 hour second hand transmmison for 6.5 k. plenty of ecspensif engines and cars builds on this forum nothing is cheap. so that one thuse not hold any merrit. fact is there are lots of euro 6/7 speed racing overdrive transmissions. and like i said overhere things go a lot faster on the euro tracks.

[andrewb70]

NOP they are not 25 k and iven if they are. They are very strong OVERDRIVE racing transmissions. one link i put on was a 24 hour second hand transmmison for 6.5 k. plenty of ecspensif engines and cars builds on this forum nothing is cheap. so that one thuse not hold any merrit. fact is there are lots of euro 6/7 speed racing overdrive transmissions. and like i said overhere things go a lot faster on the euro tracks.

Bless your heart. You got it all figured out.

Andrew

[Roadrage David]

thank you apresiate it!!!!!!!!!!!!!.......

[ace_xp2]

Uhh, ever wondered what would happen if you take a 2:1 gear and flip the gears to opposite shafts? Now the question is, what makes this new ratio weaker then the original positions?

[iadr]

Uhh, ever wondered what would happen if you take a 2:1 gear and flip the gears to opposite shafts? Now the question is, what makes this new ratio weaker then the original positions?

Nothing. Same strength, which is what are all all trying to explain to Andrew.

[andrewb70]

Guys,

Racing transmissions are a whole different deal. What I was referring to were street transmissions like a T56, TKO, and the LGT. For instance, in a T56, the overdrive gears have a much steeper angle than gears 1-3c(4th is direct drive), which makes them weaker, as compared to a racing transmission that has straight cut gears, regardless of being under driven, or overdriven. It is the high angle of the gears that makes them weak.

There is also an efficiency argument for using direct drive in racing application, because the power flow is more direct.

The other concern with setting up a car for high speed driving using overdrive gears is driveshaft speed. When using an overdrive trans it is tempting to run low rear end gears, which increases driveshaft speed for any given vehicle speed. If you were to run 4.10 gears, it wouldn't be very hard to approach 9000rpm at the driveshaft with vehicle speed of about 170mph (running a 26.5" tire).

Andrew

[andrewb70]

Look at the gearing of a new C7 Corvette automatic:

http://en.wikipedia.org/wiki/GM_8L90_transmission

I guarantee you that top speed is reached in 6th gear, which is 1:1.

Again, racing transmission are different.

Andrew

[iadr]

Ok, and there I can agree- driveshaft speed concerns me as well. There is a poster at Speedtalk (MadBill) who runs a GT1 car, and noted that the driveshaft speeds he is hitting at some fast tracks are over 10K. It's a Merkur bodied tubeframe car running a SBF (nascar take offs) and an O/drive trans. 10K plus... Thats enough to worry me.

The angle in top gears 5/6 both is to keep the gear noise down. If, say, G-force or the guys who started this thread, tool up and make replacement gears with a shallower angle, then there is no reason why 5/6 can't be the strongest in the box.

OE gears on the vette are a weird compromise deal- EPA fuel ratings etc. Remember the solenoid to go from 1 to 4th Vette's used to have? Same deal, just more subtle. Performance or technical reasons are very far from some choices.

[andrewb70]

Ok, and there I can agree- driveshaft speed concerns me as well. There is a poster at Speedtalk (MadBill) who runs a GT1 car, and noted that the driveshaft speeds he is hitting at some fast tracks are over 10K. It's a Merkur bodied tubeframe car running a SBF (nascar take offs) and an O/drive trans. 10K plus... Thats enough to worry me.

The angle in top gears 5/6 both is to keep the gear noise down. If, say, G-force or the guys who started this thread, tool up and make replacement gears with a shallower angle, then there is no reason why 5/6 can't be the strongest in the box.

OE gears on the vette are a weird compromise deal- EPA fuel ratings etc. Remember the solenoid to go from 1 to 4th Vette's used to have? Same deal, just more subtle. Performance or technical reasons are very far from some choices.

G-Force does have different 5th and 6th gears available for people that want to use a T56 for road racing. Click on the gear chart in the link below.

http://www.gforcetransmissions.com/tran_gt-56.asp

The skip shift solenoids are alive and well and are still being used in the C7 Corvette with the TR6070 transmission which actually has 3 overdrive gears.

[mmosley]

How about converting your T56 Magnum to sequential.

http://www.ppgearbox.com.au/page.asp?productid=137

Ratios: 2.437/1.611/1.228/1.00/0.875/0.777

Dederich can handle this work stateside: http://www.dederichsmotorsports.com/

[Roadrage David]

what would be the driveshaft speed at 191mph http://youtu.be/zn3K6d_e7bw http://youtu.be/7Dp0PngisVI 0.67 overdrive 26 inch tires 3.42 ratio!!. Anyway there are people umongst us that go behond a autocross. and you can drive perfectly on the streets with a wel prept raceing transmission.

[andrewb70]

what would be the driveshaft speed at 191mph http://youtu.be/zn3K6d_e7bw http://youtu.be/7Dp0PngisVI 0.67 overdrive 26 inch tires 3.42 ratio!!. Anyway there are people umongst us that go behond a autocross. and you can drive perfectly on the streets with a wel prept raceing transmission.

The driveshaft RPM for that scenario is just shy of 8500 rpm. Depending on driveshaft length and material, it could be OK.



Andrew

[Bigblue73]

Lets get back to the Legend Transmission.

Does anyone know whats going on with it? I'd really like to know spec's on it - not just the gear ratio's such as input retaining collar diameter, isolation mount location with dimensions from center lines or common datum reference points, input shaft lengths....etc. I've looked and came up with nothing.

[andrewb70]

Lets get back to the Legend Transmission.

Does anyone know whats going on with it? I'd really like to know spec's on it - not just the gear ratio's such as input retaining collar diameter, isolation mount location with dimensions from center lines or common datum reference points, input shaft lengths....etc. I've looked and came up with nothing.

Here are some of the dimensions:

http://bowlertransmissions.com/p/522...mission-custom

As for input shaft length and bearing retainer, it will be the same as a Muncie. Bearing retainer to bells housing is 4.68", and the snout is 1.379". As I understand it, this trans is meant to plug right in where a Muncie, T10, Richmond, or TKO used to live.

I can't seem to find the trans mount dimension.

Andrew

[quarterbooty]

I just finished up installing an LGT-700 behind an LS7 in my '72 Monte Carlo. I'm using an aluminum 621 bellhousing from American Powertrain with the LS bolt pattern (standard Chevy minus 1). The LGT-700 mounting pattern is the same as a Muncie, so there are several scatter shield options available as well (e.g., Quick Time). I have a McLeod RST clutch (for LS) and a Powermax hydraulic release bearing. It all works great together.

The 68-72 A-body trans tunnel is notoriously tiny, but the LGT-700 fit without any tunnel modifications besides cutting an access hole for the shifter. My trans is setup with the SO7 shifter position (offset to the driver's side). I tried to use an American Powertrain X-Factor crossmember, but the mount boss on the transmission case was too close to the case body and didn't provide clearance for the wide mounting section. I ended up using my factory cross-member for a TH350. The cross-member didn't require any modifications, but I did have to drill new mounting holes (further back). This is likely a product of my mounting configuration. I used Dirty Dingo Slider engine mounts and have the engine placed close to the factory position, but probably a little further rearward.

My driveline angles were not optimal. The engine was down 6.5 degrees, the pinion was up 1.5 degrees, and the drive shaft was at 0 degrees. I couldn't raise the trans without cutting the floor, so I followed Andrew's lead and went with a Driveshaft Shop custom drive shaft with a CV joint at the trans. I haven't experienced any perceptible vibration to date.

Overall, I'm satisfied with the transmission. I don't have many miles on mine yet, but so far, so good. Shifts are precise and crisp, and I don't hear any gear noise that others have reported. I did have to replace the output shaft seal (leaking), but no problems since. My biggest complaint is the lack of documentation available from Legend or anyone else for that matter. The only documentation that Legend provided with mine was the recommended lubrication and quantity. There are simple things that would be beneficial to publish. For example, the reverse light switch is the same as a TKO600. The driven speedometer gear is the same as a T-5. A Weatherpak connecter will work with the neutral safety switch. Jeff Spraker (the dealer I purchased mine from) is in the process of developing a reference manual, but I'm not sure what the status is. If anyone else has questions, I'll do my best to answer them.

Nick

[andrewb70]

Nick,

Thanks for the write-up. Your front operating angle is right where mine is, which I think is pretty common with LS a-body swaps. Using a driveshaft with a front CV is the only way to cure this.

Andrew