Digger48

I second the trailer suggestion. Even though you may not be towing a long distance a trailer will be easier and safer in the long run. And a better choice over a dolly.

Thanks, Mike. I presume then that the voltage regulator is the micro-wire wrapped bar and points built into the temp gauge? I have examined it, see no broken wires or connections, emery-papered the points and hope that gets the gauges back working again.

https://photos.google.com/photo/AF1QipM7FZBzwY2v-o41XXsWRMNeZu-hFWymsqm-q63s Vehicle: 1973 PL 620 -- Can anyone tell me what the small (about 1" cube) electrical box fastened to the back of the speedometer is? It has 3 wires connecting (green, red & yellow). The only thing that comes close in the service manual wiring diagram is either the voltage regulator for the temp-fuel meters or something labeled as "amp" with a connection to the "spd sw." The temperature and fuel gauges are both not working. Based on the threads I've found on Ratsun (and the info in manuals) the likely culprit is the temp-fuel voltage regulator. Some of the threads have indicated that the VR is built into the temp gauge. If that is the case (and my temp gauge does have what Datsun Mike posted as points and a bar with white wire) what's the electrical box?Hopefully my attached picture URL works and you can see what I'm referring to. One possibility with the "spd sw." might be the old retarded vs. advanced timing points that the original 1973 620s had (which I long ago by-passed). Anyone know? Thanks.

That's what I thought. Thanks, guys. All the switches I have are ON when extended. I'll look for a new switch.

I replaced the stock 4-speed in my 1973 620 with a rebuilt 5W71B 5-speed, reportedly from a '77 620. It didn't have a reverse or neutral switch when I first got it so I used the reverse switch from my '73 4-speed. Now my back-up lights are on whenever it is not in reverse and off when it is in reverse. The switches I have from the 4-speed are "on" (continuity between the two wires) when the plunger is not compressed and "off" when the plunger is compressed. Did Datsun reverse that switch configuration for the 5 speed? I am assuming the proper tapped hole for the reverse switch is the one in the main (or front) casing), as indicated in the service manual, and that the only other tapped switch hole (in the rear housing near the shifter) is the neutral switch. Is it possible the fork rod for reverse-5th was improperly installed? If that were the case, why would all other gears besides reverse allow the plunger in the switch to be extended? Any advice appreciated. (And, yes, I know I don't really need a back-up light ? )

Thanks for the suggestion. I did check the baulk ring to gear clearance with baulk ring pushed fully toward gear. The service manual recommended space of 1.2 to 1.6 mm was more than double the approx. 0.6 mm I had with 4th and 3rd gears.

Thanks for the info. In checking with Transmission Exchange in Portland I am unable to get a kit with baulk rings, seals, gaskets, etc. for this 4-speed. The Datsun dealer said most of the parts are available, but their prices are pretty high (quoted me $56 per baulk ring -- ouch), so I have decided to put this 4-speed back together as-is (with the very-likely worn baulk rings) and look at the 71B 5-speed. I will give this 4-speed (F4W63) to anyone who wants it.

Thanks to both of you for your replies. I will see if I can figure out how to implement a "stop" to prevent the rod from going too far forward into 4th. But before I do, do either of you have an answer to the question: What was the likely cause of the grinding when shifting? Was it merely wear of the baulk rings? Thanks.

A couple pictures that I'd intended to include in the original post-- (I hope) -- am not doing something right for copying the url....

I have a 4-speed transmission (F4W63) from a '73 PL620 that got stuck in 4th gear. I'm trying to figure out why. I bought this one for $100 from a guy who was planning to put a 5-speed in his truck. I took it home, drained the fluid from it, opened up the bottom cover plate to examine it, didn't see any metal pieces, or any obvious problems, so I installed it in my truck and filled it with gear oil and it seemed to work adequately. However, I noticed right away it tended to grind gears when I shifted, unless I slowly eased it into gear. After driving it around town a few times (well under 100 miles) it got stuck in 4th gear. (I found a 5-speed from a '77 620 (a FS5W71B) but am going to have to rebuild it -- but that's another story.) Before taking on the 5-speed I decided I would see if I could figure out why my 4 speed got stuck in 4th. So I started to disassemble it. Mind you, I have no experience, skill or proper tools (like a press or bearing puller) to attempt a transmission rebuild but I thought I might sharpen my teeth (bad gear pun) on the 4-speed. I am part way into it and have a few questions I'm hoping one or more of you experienced folks may have some answers to. What I found: -- This transmission had been opened up before (excessive gasket cement, a few marks like someone had banged on a piece or two with a tool or hammer) -- Upon removal of the detent plugs, the springs came out, but the check-balls would not roll out despite my efforts of turning the case over and tapping with a non-metal mallet, spraying solvent up into the tubes, blowing compressed air in the tubes, and trying to loosen them with an ice pick. I later got them out after removing the selector rods. They were apparently gunked with dirty grease and would not release. -- In removing the selector rods I may have damaged one of the interlock plungers and at least scraped one of the selector rods.. In hind-sight I should have removed the tension pin on the 3rd-4th selector fork and tried to move the rod to a neutral position before driving out any of the rods. https://i.postimg.cc/cJHmvmpX/revrse-selector-rod-damage.jpg][/url][/img] https://i.postimg.cc/c4yXFf3L/Damaged-interlock-plunger.jpg][/url][/img] -- The reason it was stuck in 4th was the 3rd-4th coupling sleeve had moved so far forward (onto 4th gear) that it would not come back to neutral -- likely because it had gone beyond the edge of the synchronizer hub and one or more of the shifting inserts had moved and blocked it. I could not even pry it back with a screw-driver. [/img] https://i.postimg.cc/YCt8Hkbc/stuck-in-4th-label-comprssd.jpg][/url][/img] -- When I withdrew the main shaft assembly (which separates from the main drive gear between the 3rd-4th synchro assembly and 4th gear) 2 of the 3 shifting inserts popped out along with the forward spread spring. The coupling sleeve remained on the main drive gear (4th gear) but came off easily once the synchro hub and inserts were out of the way. -- Reverse spur gear had chipped teeth (yet no metal was found in bottom of case). My Questions: -- Why would the coupling sleeve have moved so far onto 4th gear? Is the only thing preventing that from happening the check balls and indents in the selector rod? If so, is it possible that the gunked up check-balls might have failed to stop the selector rod from going too far? And, if I cleaned the detent tubes and assured the springs were good, -- Was the original grinding when shifting gears likely due to worn baulk rings? Would that have had any relation to the coupling sleeve going too far? The big question: Assuming I can even get a new interlock plunger; in light of the damage to the selector rods should I bother trying to rebuild this?

Trying again to insert a photo. They showed up on my response post...(I'm not finding this new format very friendly). I am seeing the right side of a transmission here. Is this not getting through?

Mike, Here are three pics of a transmission that a yard in Oregon says came from a Datsun. I am hoping to find a 71B for my L16 engine. None of the transmissions pictured in that tech bulletin you sent are exactly like this. Any idea what this might be? (The other transmission I mentioned was definitely a 4-speed as it had the 6-bolt cover plate). The (8) 1174 number may be a Hollander reference number (according to the yard owner) but I can't find a Hollander table or site to check that. Thanks.

Mike, The first transmission was the original ('73). It started making a rattling noise in 3rd & 4th gear. When I dropped it and opened it up I found that one of the main shaft bearings had a broken bearing cage (that keeps the ball bearings equally spaced). I found I could get a new bearing for about $150 but when I started looking at what it would take to replace it, I decided it required skill, tools and savvy beyond my pay grade. So I happened on to a guy who was rebuilding a '73 620 who wanted to replace his 4-speed with a 5 speed and sold me his for $100. I cleaned it, looked inside for any broken gears and, not seeing any, put this 2nd tranny in my truck. I put new fluid in, a new clutch and pressure plate and started driving it. The clutch seemed to work fine. At first I noticed that this 2nd transmission was a bit touchy going into 2nd, so I just shifted slowly and eased it in without grinding. After maybe only a hundred miles of driving , it started getting touchy going into 3rd and 4th. Then as I was driving home it would not come out of 4th gear. The clutch worked OK (I sat in the cab and depressed the clutch so it would roll onto the flat bed to get home). In neither transmission did it grind going into reverse. I assume that just a visual is how you would check slave movement. How can you tell if the slave needs bleeding? Thanks.

Mike, You're amazing! Thanks for the information. I'll look it over closer tomorrow and return to the yard when I can to check those transmissions again. I appreciate the help. --Ed Fischer