5-speed L-series transmission ID

Engine, Transmission and related drivetrain.
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Dave Patten
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Re: 5-speed L-series transmission ID

Postby Dave Patten » 01 Mar 2011 08:54

rc240z wrote:As for durability, the comp boxes are pretty tough, but we see racing 510's eat them periodically...


Been there, done that with an Option 2.

They would live very well in a street car but with a GT-3 L20B and a heavy handed operator you can definately kill one.
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Re: 5-speed L-series transmission ID

Postby Dave Patten » 01 Mar 2011 09:59

I missed the telltale sign of an OD dogleg gearbox.

Look at the initial picture Okayfine posted. Just forward of the transmission mount is a large flanged nut that points at the ground when the transmission is installed. This is part of the shift linkage and holds a bell crank that reverses the direction the 4-5 shift rod travels. If you have never taken apart a dogleg gearbox, this part is a PITA to align and engage when installing the tailshaft housing.

There is a selector arm that swings side to side within the tailshaft housing as you move the shifter right and left thru the neutral area. This selector arm engages in a slot in the end of the shift rods and as you pull the shift lever fore and aft it engages the gears in that part of the "H" pattern by pushing/pulling on that particular shift rod. You pul the shift lever back and the engaged shift rod moves forward because of the shift lever fulcrum action.

The dogleg OD gearbox uses this bell crank linkage to change the direction the 4-5 shift rod moves. In 4th gear the transmission runs straight thru the input shaft to the mainshaft for the 1:1 ratio. This means the 4-5 shift rod needs to move forward to engage this coupling ring. The fulcrum of the shift lever pulls the selector arm rearward not forward. This is why 4-5 uses a bell crank between the selector arm and the shift rod , so it will reverse the shifter action to the 4-5 shift rod.

The flanged nut is the telltale that the 4-5 shift linkage includeds a bellcrank.
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Re: 5-speed L-series transmission ID

Postby okayfine » 01 Mar 2011 10:34

Well, someone glued the input shaft cover onto the bellhousing, and it doesn't want to come off with moderate force. I estimated the center of the layshaft bearing based on the relief cast in the cover, and measured CTC to the input shaft. I got something approaching 64.5mm with this method.

It would appear this is just a long, L-series dogleg.
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Re: 5-speed L-series transmission ID

Postby hammer_down » 01 Mar 2011 12:22

PISS.....
Julian,
Like I said this trans came out of a friends 240Z, back in the late 80's. Then it went into my 3.1 power 260z in 1990-ish. I ended up curbing the car about 3 years later and bent the uni-body. Parted the car and kept the trans and a few other parts. At the time I bought it, I didn't care what it was since it came out of a strong 240Z. Never gave me any trouble but I didnt' beat it either.

What do you want to do. I don't want you to feel ripped off. Cash back?

Let me know and we will work something out.

send me an email...

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Re: 5-speed L-series transmission ID

Postby okayfine » 01 Mar 2011 12:59

hammer_down wrote:What do you want to do. I don't want you to feel ripped off.


Public reply to say I don't feel ripped off. 'Tis why I hadn't bothered to mention where the trans actually came from. I just wanted to ID the trans so I knew what it was - and mostly just because I had finished datzenmike's trans article and the trans I had didn't match up to anything.

Will PM.
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Re: 5-speed L-series transmission ID

Postby datzenmike » 01 Mar 2011 13:12

okayfine wrote:Well, someone glued the input shaft cover onto the bellhousing, and it doesn't want to come off with moderate force. I estimated the center of the layshaft bearing based on the relief cast in the cover, and measured CTC to the input shaft. I got something approaching 64.5mm with this method.

It would appear this is just a long, L-series dogleg.


Julian, this is the best method I have found to break loose (without breaking) the cover plate from the front of the transmission. Just hammer on an extension through the shift arm hole.

Image


Also the dogleg cover plate has 7 hold down bolts around the outside, the FS5W71B has 5.

Dogleg left and 71B right
Image
.
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Re: 5-speed L-series transmission ID

Postby datzenmike » 01 Mar 2011 13:22

Dave Patten wrote:I missed the telltale sign of an OD dogleg gearbox.

Look at the initial picture Okayfine posted. Just forward of the transmission mount is a large flanged nut that points at the ground when the transmission is installed. This is part of the shift linkage and holds a bell crank that reverses the direction the 4-5 shift rod travels. If you have never taken apart a dogleg gearbox, this part is a PITA to align and engage when installing the tailshaft housing.

There is a selector arm that swings side to side within the tailshaft housing as you move the shifter right and left thru the neutral area. This selector arm engages in a slot in the end of the shift rods and as you pull the shift lever fore and aft it engages the gears in that part of the "H" pattern by pushing/pulling on that particular shift rod. You pul the shift lever back and the engaged shift rod moves forward because of the shift lever fulcrum action.

The dogleg OD gearbox uses this bell crank linkage to change the direction the 4-5 shift rod moves. In 4th gear the transmission runs straight thru the input shaft to the mainshaft for the 1:1 ratio. This means the 4-5 shift rod needs to move forward to engage this coupling ring. The fulcrum of the shift lever pulls the selector arm rearward not forward. This is why 4-5 uses a bell crank between the selector arm and the shift rod , so it will reverse the shifter action to the 4-5 shift rod.

The flanged nut is the telltale that the 4-5 shift linkage includeds a bellcrank.



Most interesting info. Always wondered about the shift action and that bolt.

Dave Patten wrote:datzenmike,
I would assume the OD comp boxes were the same shift pattern as the DD comp boxes. I have owned all 4 ratios of direct drive comp boxes and they were all dogleg patterns. It is sweet for racing, no ugly 4-5 shift. Very few times would you ever use 1st on the track so the complex dogleg 2-1 down shift is avoided. Makes it a simple 2-5 "H" pattern.



Duly noted, DD competition boxes are dogleg pattern.

Here is a 71B and a dogleg and you can see by eye that the 71B has larger bearings and gears because if the large 71mm spacing.

Image
Last edited by datzenmike on 01 Mar 2011 13:31, edited 1 time in total.
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Re: 5-speed L-series transmission ID

Postby okayfine » 01 Mar 2011 13:28

Actually pulled eight bolts off the cover. Threw me for a loop after reading the same in the article. Seven bolts around the edge, though, and I don't know if the eighth (inside of the fork pivot) actually secures it.

Don't think I'm going to bother pulling the cover. Everything points to a long dogleg with brass syncros.
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Re: 5-speed L-series transmission ID

Postby datzenmike » 01 Mar 2011 13:37

Yeah it likely is 8 securing bolts. You can actually see the 8th middle one in the cover picture. (I thought it was and oil hole. The only picture I have of the front of the tranny has the input shaft hiding this bolt.

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Re: 5-speed L-series transmission ID

Postby Dave Patten » 02 Mar 2011 06:17

In my quest for additional info on the OD comp boxes, Todd Walrich of Wolf Creek Racing provided me with the following picture. This is a close ratio Datsun Comp gearbox. The shifter is a "B" type, but the output is a flange (Roadster type) not a slip yoke.

From his research, all comp gearboxes until around '79-'80 were flange output. They then went to the slip yoke style that is most commonly seen. He also confirmed that the comp OD boxes were NOT dogleg pattern (as did a review of my Motorsports Schematic Catalog).
Attachments
OD Comp Box.JPG
OD Comp Box.JPG (122.74 KiB) Viewed 3591 times
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Re: 5-speed L-series transmission ID

Postby datzenmike » 02 Mar 2011 08:44

DD are dogleg shift pattern.
OD are regular pattern with flange before '80, spline after.

Thank you Dave for sharing this. While most will never even see one of these it's still worth having out there. Who knows what is out there in someone's garage.
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Re: 5-speed L-series transmission ID

Postby iceD » 02 Nov 2013 10:19

What shift pattern would a 1975 620 5 speed have/ Are there any external features to indicate what the transmission is other than what has been mentioned here and there.

viewtopic.php?f=30&t=25454

Respectfully, ice D

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Re: 5-speed L-series transmission ID

Postby bertvorgon » 02 Nov 2013 10:26

this is my spare comp box, with the flange style.
Attachments
IMG_2470.JPG
IMG_2470.JPG (147.11 KiB) Viewed 3252 times
close ratio comp box, with flange mount.JPG
close ratio comp box, with flange mount.JPG (133.74 KiB) Viewed 3252 times
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Re: 5-speed L-series transmission ID

Postby datzenmike » 02 Nov 2013 20:12

iceD wrote:What shift pattern would a 1975 620 5 speed have/ Are there any external features to indicate what the transmission is other than what has been mentioned here and there.

viewtopic.php?f=30&t=25454

Respectfully, ice D


Well first there was no 620 5 speed option until '77 so it could be from a later 620. a first year ('80) 720, a 280z or 280zx or an 810 Maxima. These 71B transmissions are absolutely drop in and go with zero modifications. Measure the length from block to the driveshaft... if 31.5" this is what you have.

If the bolt that holds the speedometer pinion sleeve into the tailstock is down at the 6 o'clock position then it's an '80 or newer transmission can this will narrow it down to either a 280zx, Maxima or '80 720 box.

The shift pattern would be...
1.3.5
2.4.R
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Re: 5-speed L-series transmission ID

Postby iceD » 03 Nov 2013 09:25

Thanks Mike, I have not seen the transmission yet. I will take a few pics later today.

ice D


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