620 L18 5-speed options

[Kirden]

Hey guys, I was wondering if you could point me in the right direction for a donor car to grab a 5-speed tranny from for my 74 620. I had originally wanted to stick with the 4-speed but since I have to drive 60 miles on the highway every day I feel the 5-speed may help my little 620 live a longer life.

 

I'm mainly looking for a list of vehicles that will have a 5-speed tranny that will bolt up and not require me to replace my drive shaft. Also, are there any changes I can make to the 4-speed or rhe rear end until I can get a 5-speed that will make highway driving less problematic? Having the truck at such high rpms the entire way to work makes me feel like I'm just asking for trouble.

 

Thanks for any tips and have a great day.

[ggzilla]

There is only one bolt-up, the FS5W63A to replace the F4W63.

 

FS5W63A

* 1977-1979 200SX

* 1978-1979 510

 

There are "shorty" truck five speeds that do not require a driveshaft changed, but they do require a customized transmission mount.

[Laecaon]

What is high rpms? L18s love to rev.  Keep it oiled and all should be fine.

 

But really, you could put in some 3.89 or 4.11 rear end gears.

[datsunaholic]

It's a '74.  They use a 71B longtail, at least all the ones I've seen.  So a 77-79 620, 80 720, or 77+ 280Z trans is a drop-in replacement.

 

Only the 72-73 620 used the short trans.

 

But- since there are rumors early 74s may have used a shorttail, the way to tell is look underneath.  Big square pan bolted to the bottom?  63-series, then the above post applies.  No square plate?  71B. 

[Kirden]

Alright, thanks for that, can you go ahead and list the "shorty" ones as well? My local shop can most likely fab a mount, I just don't trust them with their custom fab driveshafts and I have heard horror stories about some shafts coming loose while driving, poll vaulting trucks because people around here don't know how to secure them correctly.

 

Also, will a rear end change make the 4-speed viable or is that pretty much out the window as far as 65+ highway speeds are concerned?

[Kirden]

wow, my slow response times ftw. I will get under the truck later today and take some pics of the tranny. Maybe I can find a model number. As far as how high, I'm not sure, it just sounded way too loud. If I can find a cheap tach I can geet a better reading on it but seeing as I just bought the truck about 16 hours ago I haven't put much into it yet. I just want to cover my bases since it will be my DD starting next Monday.

[ggzilla]

The 4-speed is viable with the stock rearend. L18s love to rev. The redline is 7000 RPM. You are nowhere near that at 65 mph.

[Kirden]

Haha, guess I am getting scared for nothing. Maybe it is my throttle cable then because even with the pedal to the floor going down hill I can't get past 70mph. We start the brake tear down tomorrow so I should be able to take a closer look at the truck. Thanks again for all the info. I have already sourced a possible 79zx tranny for a swap just for the upgrade.

[Kirden]

Post removed, meant to post this in my build thread not the trans thread.

[Kirden]

Post will be removed, don't want to step on any toes.

[Kirden]

Alright, finally got everything rolling on a 5-speed. Picking up a 79 ZX 5-speed from DTP (thanks man :) ). New questions because the threads I have looked up give some slight differences of opinion.

 

Will the 79 ZX tranny need to have a custom mount? I saw a post where someone stated that the Z or ZX (can't remember which) tranny is slightly tilted when bolted to an L series engine so I want to make sure I am prepared if I need a new mount.

 

Will I want to remove my speed gear from the 4-speed to keep the speedo accurate? Currently the speedo isn't working correctly anyway which is most likely the speedo cable needing to be replaced, but I would like to eventually have an accurate speedo. Maybe I should just look into a GPS speedo?

 

Should I worry about changing the rear gears? As far as I know I have the stock 74 620 gear set for a standard cab. I am looking for a good balance between highway mileage and decent take off speed. Nothing race worthy, but enough to be able to enter a main road from a side street without backing up traffic :P

 

Again, I have looked for most of this information but there are a lot of different opinions. Having some overall concrete answers would be great so I can purchase everything I need for the swap and be prepared.

[datzenmike]

It will fit perfectly on your 620 4 speed mount. When installed you won't be able to tell the difference. No need to change the rear end. The '79 has a closer ratio gear set than those in the old 4 speed. What this means is you may notice a very slight increase in effort starting from a stop, more so if carrying a heavy load. It may travel slightly further before it feels right to shift into second and third but forth will be the same. If you are not carrying any loads and using the truck for commuting to work this tranny is ideal.

A 5 speed will not make it go faster. If you can't go over 70 in 4th gear it sure won't in 5th. Fifth gear is simply to lower RPMs at highway cruise speeds.

Before I forget. Remove the speedo pinion sleeve in the tailstock while the tranny is out and swap into the '79zx 5 speed. The speedo pinion gear is matched to your rear end gear ratio to keep the speedometer accurate. The pinion in the zx is matched to a different tire size and rear end ratio. Off hand I don't know if it will work or not but I do know that the 4 speed one IS. So swap it.

There is a 10mm bolt and key that holds the pinion in place. Take the cable off, remove the bolt and key and pull the pinion straight out... avoid twisting as it could damage the plastic gears.

I just happen to have a '79zx tail....

 

 

The pinion sleeve holds the pinion gear. This one is a BLUE (color code) 18 tooth cog. If your 4 speed cog is the same color as the zx you can use either.

.

[ggzilla]

L-series transmission has 12 degree tilt anti-clockwise

Z-series transmission has slight tilt clockwise

 

280Z and 280ZX both use L-series engines and L-series transmissions.

Newer 720 and S110 use Z-series engines and Z-series transmissions.

[Kirden]

The problem with 70 in 4th wasn't the tranny really, it is a combination of things. For one my gas pedal bracket is bent, so I have very little pedal travel till it hits the floor. That is probably the biggest reason. Also, the manual choke on the retrofitted GM carb (gotta love thos shade tree mechanics) closes itself, meaning if I try to pick up speed I have to hold the choke lever where I want it...

 

I have a pedal assembly coming in from another ratsun member and I will pick up a weber carb and a timing kit/chain (have a severe shearing metal rattle at high rpms) with my next check.

 

Luckily this truck will not be doing any heavy hauling. Maybe a bed or dresser here and there, but no really heavy duty work (except maybe parts :P ). I'm glad this transmission will work without any special hardware, that clears up a lot of my worries.

[Kirden]

L-series transmission has 12 degree tilt anti-clockwise

Z-series transmission has slight tilt clockwise

 

280Z and 280ZX both use L-series engines and L-series transmissions.

Newer 720 and S110 use Z-series engines and Z-series transmissions.

 

Oh wow, I feel tardid... Thank you for that. I can't believe I asked that question when all day I was talking with Datsun Parts LLC about their L28 build which are for... 280z-zxs... That was a real duh moment :P

[sedition88]

Having the same truck, this is great info to have for the future :thumbup:

[Kirden]

Ah thanks for the update datzenmike. That helps a ton. I will be sure to check the pinion gear. I'll even post a pick on here if I think about it since I'm sure others have asked this question before.