Let's play, "what transmission is in my truck?"!

[ducky]

Hey guys. Starting to drive the truck more, but seriously need to fix... everything, before I kill myself in it.

 

Need a clutch, but have no clue what trans is in my truck. It's a 5 speed. Truck is a 1976 even though the title says 1974, not that it matters, since Haynes says no 620 had a 5 speed.

 

Apparently, imgur doesn't work here for thumbnails.

 

http://imgur.com/a/uIvcjX1

[DanielC]

It really does not matter what transmission you have, the clutch is engine specific.

In the 45 or so years since your truck left the factory, there is a pretty good chance somebody changed something.

Below the number three or four spark plugs, conveniently behind the oil dip stick is an angled raised boss with the engine type, and the engine serial number. 

1976 620 trucks had a L-20-B engine from the factory, and as far as I know, that engine either had a 225 MM clutch disk, or a 240 MM clutch disk.

If the serial number on the engine matches what the truck left the factory with in 1976, you should be able to just order a clutch disk, pressure plate, and throwout bearing to do the clutch job, using the correct year, make and model of your truck.

 

If the engine has been changed, I would suggest taking the clutch out to get the correct one for your truck.

Any L transmission will bolt on to any L engine.   You can bolt a 280ZX transmission to a L-16 engine, or the L-16 transmission to the 280ZX engine.  

To accommodate different pressure plate heights, the collar that holds throwout bearing has different heights.  So the collar matches the pressure plate, and the pressure plate matches the clutch disk, and clutch surface on the flywheel.  

There are six bolt flywheels, and five bolt flywheels.  Five bolt flywheels were used on most L-16 and L-18 engines, although there was a six bolt crankshaft available long ago for the L-16, and L-18, as a competition part.   L-20-B engines used the six bolt flywheel, as did the six cylinder L-engines.

[datzenmike]

The 5 speed is in the supplement in the back of the Haynes book.

 

 

Build dates (see tag on door jam) from August '76 on, (beginning of the '77 model year) were available with a 5 speed. Only 4 speeds before this unless swapped in.

 

As Daniel said the transmission is irrelevant to your clutch choice, only the flywheel determines the pressure plate size that will bolt on.

 

Find out what engine you have... look behind the dip stick handle on the top edge of the block just below the head. You'll have to measure the clutch disc diameter to be sure. Car L20Bs are 200mm while truck are 225mm. As there is some mix up with the year a '74 would be the only year with an L18. If it is, the clutch will be 225mm. The '74 L18 is the only L18 with a 5 bolt 225mm PP.

[ducky]

Thanks guys! For some stupid reason I thought the clutch bolts to the trans, but now that I'm remembering, the clutch does go in the engine... I always find I make easy mistakes.

 

As for the engine, it's an l20b. Just found that out last week. I had assumed the l18 was in it since the title says 1974. The door plate says 1/76 on the top number and 11/75 on the next one, so I assume that's a build date of November 75 and ship of January 76?

 

I'll get mighty lucky if the truck is better in every way than originally thought. Also, never thought to look in the supplement, even though I remember it's there.

[datzenmike]

Someone has messed with it. Can't be a '76 and titled as a '74. So either the cab (with the tag) was swapped onto the '74 or it is a '76 and someone has used a '74 title on it. Cross fingers that no one checks the frame number. The frame is stamped PL620 or HL620 top passenger side forward of the engine mount. Use a wire brush.

 

If a '74 (PL620) the car number would be above 324,001 I don't know how many were made 100-200,000?

 

If a '76 (HL620) model year the car number would be between 90,001 and 156,761. Car numbers began with 000,001 for the '75 model year because of the change to HL620 from PL620

[Valvebounce]

1 hour ago, datzenmike said:

Someone has messed with it. Can't be a '76 and titled as a '74. So either the cab (with the tag) was swapped onto the '74 or it is a '76 and someone has used a '74 title on it. Cross fingers that no one checks the frame number. The frame is stamped PL620 or HL620 top passenger side forward of the engine mount. Use a wire brush.

 

If a '74 (PL620) the car number would be above 324,001 I don't know how many were made 100-200,000?

 

If a '76 (HL620) model year the car number would be between 90,001 and 156,761. Car numbers began with 000,001 for the '75 model year because of the change to HL620 from PL620

 

Had anyone got a picture of this stamping?  All the trucks sold here were GN620's.  And as far as I know, ours got no stamping on the chassis whatsoever. (Just the aluminium body tag) 

[datzenmike]

Don't know about non N American frames.  On ours L stands for Left hand drive. P was for L16/18 and H was L20B

 

Looks somewhat like this on the 521...

 

On 3/10/2012 at 4:49 AM, DanielC said:

Here is the serial number on the frame of a 521.

Here is a picture taken farther away, for reference.

And here is a picture of where it would be, with a cab, engine, and other stuff on the frame.

 

[ducky]

Just checked mine. Couldn't read the entire number, but definitely see HL62010 which, is the beginning of the VIN on the fender.

 

Were the splines on the trans the same for all years of the 620? Were there any other ones from other cars that would mount right in? I didn't see any model numbers, so I'm assuming I'd need to get it up on a lift to really find it.

Edited July 11, 2020 by ducky

[datzenmike]

Definitely not a '74. The frame on a '74 would be PL620.

 

Here's another thing. The rad support on '74 and earlier trucks is straight across...

 

 

The '75 and later trucks have a bend for the larger rad used with the larger L20B engines...

 

[ducky]

I got the bend, yo. Everything points to a 1976. I need to contact the BMV to have them fix the title, I think...

[DanielC]

I would leave the title alone.  In some states, 1975 is a cutoff date for emissions testing.   Vehicles built before 1975 do not require testing.

[ducky]

7 minutes ago, DanielC said:

I would leave the title alone.  In some states, 1975 is a cutoff date for emissions testing.   Vehicles built before 1975 do not require testing.

 

I'm in Ohio. We don't care about the environment yet.

[datzenmike]

Don't rock the boat. You legally own a '74. The '76 frame and cab may be stolen. Let sleeping dogs lie.

 

Maybe when you finally go to sell it. After all you would be knowingly selling something that might be illegal. I had a '78 the I put on an '82 frame, nothing matched but by then I would never have sold it. 

[ducky]

Hey gents. I'm back to this.

 

The bellhousing has a 3L listed on the side, which kind of seems to point to a automatic. But the rest is clearly a 5 speed. Rear diff ratio is around 2.25. What could this diff and trans come from?

 

So confused with what I have lol

 

Also, the brakes never worked great. Turns out the previous owner though it would be a great idea to flip the valve over the booster the opposite direction...

[datzenmike]

Surely you know an automatic from a standard?

 

'74 and up were 4W71B 4 speeds.

In '77 a 5 speed FS5W71B was made optional

Differential gears are all 4.375 with the exception of the '73 automatic (4.625) and the '79 with a 4.11 although the 4.375 was optional.

 

Valve? must be the one way valve in the vacuum line.

[Stoffregen Motorsports]

I suspect you were trying to count the rotations of the diff flange while spinning one tire. Am I right? Both tires need to spin one full revolution so this is actually a three person job.

[datzenmike]

Place transmission in neutral. Lift one tire and turn exactly two turns and count the driveshaft turns. 2.25 should probably be 2.25 X 2 = 4.50 but 4.375 is likely the real answer. More turns.. more accurate.

[ducky]

6 hours ago, datzenmike said:

Place transmission in neutral. Lift one tire and turn exactly two turns and count the driveshaft turns. 2.25 should probably be 2.25 X 2 = 4.50 but 4.375 is likely the real answer. More turns.. more accurate.

 

I did find this method when I looked again, and yes, we got right around 4.3.

 

I'm going to see what the FS5W71B gears were, then run some numbers on a calculator to see if my speedometer and pinion gear are aligned with that trans. Hopefully they match, so I can make the assumption that's what's in the truck.

[datzenmike]

 So you think you have a '76 but it has a 5 speed in it?  The '76 4 speed should have a Red plastic gear, so remove the speedometer pinion sleeve and look. If it's Red it matches the 4.375 differential.

[ducky]

26 minutes ago, datzenmike said:

 So you think you have a '76 but it has a 5 speed in it?  The '76 4 speed should have a Red plastic gear, so remove the speedometer pinion sleeve and look. If it's Red it matches the 4.375 differential.

 

White 19 tooth. I just ordered the purple 21 assembly based on info from another thread. I'm 10 mph off, so that seems right to me. Just changed the speed cable, and its so awesome to have a stable speed instead of bouncing around lol

[datzenmike]

10 MPH off at what speed??????? If at 100 that's 10% but if 10 off at 50 that's 20% BIG difference.