CamoKing Posted August 30, 2019 Report Share Posted August 30, 2019 (edited) Good day master mechanics! (looking to the rear, passenger side): Another mystery emerges from my refurbishment of this '82 4x4 720, Z22 --- Something is missing on the transmission's rear extension case that I think is supposed to be a neutral switch. BUT the hole/threads are much larger than that of the reverse lamp switch found on the front case. It doesn't look designed to accept the switches I see from my web searches. (Close-up of this threaded fitting on the transmission rear extension case) I find dangling wires that do match what the manual shows for a 'neutral switch'; they could reach this open spot. It looks like this is the original 4-speed for this truck. My manual indicates F471B . I see ZL71B #1 (no F4) ....I don't know if the 'ZL' means something else. Maybe this is NOT the original transmission? (Close-up of this threaded fitting on the transmission rear extension case) (Reverse lamp connection and transmission ID) (This 4 is cast in the middle of the extension case) Questions: 1) If this is the original tranny, is that mystery fitting for a 'neutral switch'? 2) If so, what the heck does the switch look like and where can I get it?? 3) If NOT, what does attach to this fitting and what is it for??? 3a) What do I lose operating without this 'neutral switch'? Hot fun in the Summertime to all. Thanks. Edited August 30, 2019 by CamoKing delete phrase 1 Quote Link to comment
bottomwatcher Posted August 30, 2019 Report Share Posted August 30, 2019 Exterior threads you have a 2wd trans. Speedometer cable goes there. 4wd goes to trans case. 1 Quote Link to comment
CamoKing Posted August 30, 2019 Author Report Share Posted August 30, 2019 Me thinks something has been modified here. It is a 4 WD and I do see the speedo cable goes into the transfer case. So, it seems someone put a 2WD trans here?? Would that work as a replacement? Whatever. I still have no idea where these leads for a "neutral switch" go. 1 Quote Link to comment
datzenmike Posted August 30, 2019 Report Share Posted August 30, 2019 The 4x4 transmission has obviously been replaced with an earlier (pre 1980) L series 2wd 4 speed transmission and the Z series front case swapped onto it so it will bolt to the Z22. This is the speedometer pinion sleeve. What I did with mine is get the threaded part off an old speedometer cable and RTV the end to seal it. When cured, wrap threads with plumber's tape and screw it on to keep the oil in. Worked like a charm. This is the reverse light switch. Find two Black/Red stripe wires to connect to it. It is an F4W71B so the 71B part is correct. It can be an L or a Z series but can't be an LZ 71B so I don't know why they cast it this way. All other casting numbers are likely revisions or to identify the casting mold it came from. A transmission ID is more visual than casting numbers and letters. Often what it doesn't have for switches IDs it. Those wires should go to the neutral switch located just forward of the shifter high on the transmission. 1 Quote Link to comment
CamoKing Posted August 31, 2019 Author Report Share Posted August 31, 2019 You are so right on, Mike. Thanks for the detailed clarification. I knew that an experienced eye would solve this mystery. I will try to find the connection for the neutral switch tomorrow . THanks again. 1 Quote Link to comment
CamoKing Posted August 31, 2019 Author Report Share Posted August 31, 2019 23 hours ago, datzenmike said: The 4x4 transmission has obviously been replaced with an earlier (pre 1980) L series 2wd 4 speed transmission and the Z series front case swapped onto it so it will bolt to the Z22. I found this image on the web of a F471B that shows where the switches go. !!! The neutral switch looks to be right below the cover of the shifting rod channel. Whoopie!! So, under the truck , guided by Mike and the image above, I do find a 'hole' on the rear extension case just before the shifter under the cover . However, alas, there is no threading inside this hole to receive a screw- in switch. ): Indeed, I find this hole bottoms out and makes no entry into the shifting rod channel. The image below, taken from inside the cab, console removed, shows a slight recess in the floor of this shifter channel right opposite the likely location of a neutral switch. -- another piece of evidence that points to this being The Place where a neutral switch could be IF... I presume that this hole should be threaded and provide an opening into the channel from which a switch would make contact with the rod?? It seems this particular transmission was made for a model that did not use a neutral switch or it was located elsewhere . I sure don't know . Maybe you do. So, after exhaustive research I have to conclude that this transmission replacement was sufficient but lacked thoroughness; maybe the owner didn't have any choice. I should have known this at first sight of the dangling wires instead of crawling under with lights and mirror to get a view of this transmission case . Oh, well, at least I'm getting to know more of this 'ol truck's 'eccentricities' . I'm just wondering if the absence of this switch interferes/defeats the function of the fuel shut off system. Do fuel economy and hydrocarbon emissions really matter much? (That's a rhetorical question) Good day, Have a great weekend.! 1 Quote Link to comment
CamoKing Posted August 31, 2019 Author Report Share Posted August 31, 2019 What does this neutral switch look like anyway? Where can I get one if I need it? 1 Quote Link to comment
datzenmike Posted September 1, 2019 Report Share Posted September 1, 2019 It looks very much like the reverse switch. If the switch is not there I doubt the striking rod it rides against has been milled so it will work either. There are 3 shift rods, look at the bottom rod just below the shift fork with the roll pin on the middle shift rod. See it? There is a notch machined into it. The reverse switch is mounted on the case covering it. As the rod moves forward the switch plunger slides up that ramp and closes the contacts inside. The striking rod will need something like that. 1 Quote Link to comment
CamoKing Posted September 1, 2019 Author Report Share Posted September 1, 2019 14 hours ago, datzenmike said: There is a notch machined into it. The reverse switch is mounted on the case covering it. As the rod moves forward the switch plunger slides up that ramp and closes the contacts inside. The striking rod will need something like that. And I see nothing of the sort on the striking rod in this truck. Further evidence that changes were made without regard to original design. I'm not about to replace this transmission for the sake of one switch even if it does play a role in the design for better fuel efficiency and less emissions. The leads for this switch will continue to 'hang out'. This has been a great learning experience. Thank you, Mike, for all the feedback. Quote Link to comment
datzenmike Posted September 1, 2019 Report Share Posted September 1, 2019 Sometimes you just have to 'make do' with what you can find after 30 years, as evidenced by the Z22 front case being put on an L series to make it work. Just curious. Have a look under the right side hood hinge, on the inner fender for the engine tag. It will be stamped with the transmission used. Either F4W71B or FS5W71B. Maybe it came with a 5 speed originally? Quote Link to comment
CamoKing Posted September 1, 2019 Author Report Share Posted September 1, 2019 40 minutes ago, datzenmike said: Just curious. Have a look under the right side hood hinge, on the inner fender for the engine tag. It will be stamped with the transmission used. Either F4W71B or FS5W71B. Maybe it came with a 5 speed originally? Sho' nuff, Mike......It reads: FS5W71B. WAS a 5 speed. Quote Link to comment
datzenmike Posted September 1, 2019 Report Share Posted September 1, 2019 It was an option on 620/720 '77 trucks and on. The 4 speed was discontinued Oct '82 or a few months into the '83 model year, then only 5 speeds. 1 Quote Link to comment
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