PT81PlymouthPickup

No rush! It's been sitting in my garage for almost 20 years. Lols!

Others here might have a more definitive answer on which differential ratios were available when our trucks were first built, but I'm thinking most of the 39-47 Dodge / Plymouth 1/2 ton trucks most likely had 4.1 ratios. When I first rebuilt my truck in the late 1970s I found a low mileage 3.9 ratio pumpkin which I took out of a circa 1950 Mopar car. Other than the ratio, it was the exact same carrier (pumpkin). It worked well with tall tires. Plenty of pull on hills and lower revs on the highway as compared to the 4.1. I ended up taking it out when I installed a T5 transmission because I no longer had an emergency brake on the trans. I installed a 3.55 ratio rear out of a jeep Cherokee. It works OK, but struggles on long hills. If I were to do it over I would select a 3.73 ratio. I think several others on here might agree with 3.73 ratio as being a good choice for our trucks? Anyhow, if you want a perfect bolt in condition complete rear end with a 3.9 ratio it's free to you or anyone else that might want it. Drums and brakes are all like new as well. I won't ship it, but I'd be happy to see someone come get it that might use it.

My opinion is get a 3.73 differential! I'm running a 3.55 behind my .040 over bored 201 block in my 39 PT81 with a T5 trans. It will go up big hills but requires much shifting and I sometimes get a line of modern vehicles lining up behind me. It will cruise wonderfully at 65mph or better on a relatively flat roads. When I had my original trans with a 3.90 differential It would climb a mountain but at 55mph sounded like she would blow up from high revs. I have mixed feelings on dual anythings. Really sweet to look at, but the little extra performance we get comes along with more things to give me aggravation. Twice the carbs and twice the exhaust means twice the things to fail. I must admit I'm jealous of those cool looking dual installs. I started to go the dual route by accumulating some parts, but decided if I do anything more to the old girl, I'll install a 3.73 differential. I still have original rear end with a 3.90 gear in perfect condition if anybody wants it? (Free)

Yeah! And even with upgrades to brakes, gear ratios, and tires, which I've done, it's still a bit risky driving these old trucks at modern highway speeds. Like Young Ed indicated; how much nerve do you have? Lols! I suspect also that my truck might be easily rolled over in a high speed mishap? My 39 has the earlier design door latches which were noted for flinging open in accidents where the driver is thrown out, usually under the wreck. I try to stay off the major roads as much as possible. On the other hand, at my age, it might be a better way to go than ending up in some nursing home. Lols!

Tall 16" tires and a 3.90 differential with standard trans I had her up to 70 mph. The flathead six sounded like she was ready to blow up. Stay off the interstates! Lols!

My 39 PT81 did not have a relay when new. Perhaps by 47 they may have? But, I believe Young Ed is correct. No relay. A wiring diagram specific to your truck would be most useful. On my truck, power it's routed via the amp gauge through the harness to the horn and then back into the harness to a connector which connects to the ground wire that goes up through the steering column to the horn button. I kept mine wired this way without a relay. I converted to 12 volt many years ago. I'm still using the oem 6 volt horn and it works flawlessly. However, it rarely gets used. If I were to use it daily, a relay might make sense. I doubt you'll be using it much in a 1947 truck? The neat thing is; my 6v horn will scare the bejesus out of anyone I honk at. ? By installing a relay, the load will be carried through the contacts in the relay, that protects the horn button contact from arcing and as Ken suggests could shorten the life of the horn button switch. More importantly, whatever you decide, make sure there's a fuse in the circuit. When you start making changes like I did (12v conversion, stereo, halogen headlights, signals, alternator, electronic ignition) it got really challenging for me. Altering the harness and routing wires correctly and making it look right was no easy task. Did I mention, I had little idea of what I was doing. For me, it was the most frustrating thing of the entire build. But that's just me.

Jay Leno knows a thing about fire. ? Anybody know about these Element extinguishers? Sure looks like a good alternative to those bulky ones.

According to this Hemmings article, not until 1946? https://www.hemmings.com/stories/article/1939-1947-dodge-trucks

If you're worried about scratching up your paint job, it's advisable to have someone help you lift the windshield out. It's a bit awkward to do by yourself.

Yes, it telescopes from about 8-3/4 to 11-1/4 in length.

Thanks Ed! Yeah, I have a blade that looks like that, but it's 7-1/4" long. Does not work well at all. The one in my photos works better, but it overlaps the windshield frame which will damage the paint if I keep using it. I'm thinking there is an arm / blade combination that will work better than the original on our trucks, but sure hard to find any info on what that might be?

Not sure, but after installing a pcv valve in my 39 pickup the oil stink went away.

Oops! I got the Mopar part numbers wrong. Not positive but if I'm reading the parts book correctly it looks like: Listed for the 39 Dodge TC which I believe is the equivalent to my 39 Plymouth PT81 798484 wiper arm in black? I'm unsure how to cross reference the wiper arm in chrome? 648888 wiper blade.

I'm hoping someone may have found a wiper arm / blade combo that works well on our 39-47 cabs? I don't know for sure, but suspect the wiper arm I have in photo may be the correct one for my truck? The blade I have fits the arm nicely, but I'm almost certain it's not correct. It's too long (10 inches). It overlaps the windshield frame when running. That can't be right. The wiper blade shown in the 36-40 Dodge Master Parts Catalog looks like a simple flat squeegee. I doubt those are very effective? The OEM Mopar part numbers: arm assembly-23-67-5 and blade package-23-67-2 I'm hoping to find an NOS Trico arm and a blade that fits, works well, and doesn't overlap the windshield frame. Does not have to be exact as original. Not being a fan of repro stuff, I'm wondering if anyone has Trico part numbers for the arm and a blade that might work well? I haven't been able to determine what the correct length arm or the blade should be? I'm guessing the blade would have to be pretty short to not run over the windshield frame. Maybe 6 inches or so? Anyhow! Any experience with this may be helpful. Would be very much appreciated.

Oh yeah! It's listed on the eBay ad for 41-42 Ply, Dodge, Desoto, Chrys. ? https://www.ebay.com/itm/334221370361

Thanks again JBNeal! I found this one for sale on eBay. Looks exactly like mine. I'm going to order a C-3 filter cartridge or a cross referenced one.

Thanks JB! The dimensions for the C-3 gaskets are exactly as mine. Still available from Fram too. That Fram C-3 sure has a lot of cross references! Must of been a popular filter. I'm thinking the Fram 315 housings were not a Mopar install? Likely an aftermarket install on my truck? The oil filter housing in the 1936-40 Dodge Truck Parts manual don't look anything like the one I have. Thanks again. Very helpful.

Thanks Ed! I looked the 51076 up. Filter is about same size as what I'm using now, but gaskets are different.

My oil filter housing is probably not the one that came with the truck when it was new, but was on the engine when I bought it around 1980. I don't know for sure what the correct filter for it is? I've been using Wix 51080 which fits OK but the gasket that comes with those is not the right one for my housing. Larger gasket on right in photo is what comes with the Wix 51080 filter. Smaller gasket on left is what fits my housing lid in a grove in it. I've been making the gaskets which I'd rather not do. Anyhow, I read that Wix 51010 filter has the correct gasket dimensions to fit my lid. The filter itself does have slightly different dimensions, but I'm thinking the Wix 51010 may be the correct filter for my housing? The thing that confuses me is that I haven't yet found any Mopar application data for the Wix 51010? Anyone recognize this housing and suggest a filter number? I'm thinking it might have been off a car engine? Looks a bit smaller than other filters I've seen on trucks at car shows.

Yeah, I've never seen any brackets like those on any 39-47s.

Ed, do you have a picture of that L bracket? I'm curious to what it looks like. I've never seen one before. Also those tailgate latch brackets that are bolted on in your first photo look much heavier duty than mine. Did you take them off a heavier duty truck? I'd like to get a set like those.

Yeah, I was afraid these might not be in high demand. I hate to scrap anything especially when in perfect condition.

Back in the 70s when we first restored my 1939 Plymouth pickup, the gear set in the differential was shot. We found a replacement pumpkin in flawless condition at a junkyard and installed it into the original housing. Can't remember now, but think it came out of a late 40s early 50s car. It has a 3.90 ratio. Casting # on pumpkin is: 1141544-29. Anyhow, several years later and only several hundred trouble free miles, I decided to install a T5 transmission and while doing so also installed a differential from a late 1980s Jeep in order to get the parking brakes and self adjusters. The entire rear end with backing plates, new shoes, cylinders, and perfect drums has been stored in my garage ever since. I'm on a mission now to clean out my garage. Anyone have an idea how to identify this rear and what it will fit? I'm fairly certain it will fit 39-47 1/2 ton trucks, but might it fit other ones as well? I'm curious if it has any value, but mostly would like to see it go to a worthy project and not end up in scrap. I also still have a spare set of axles and a driveshaft. I'm going to advertise on eBay or Craigslist once I figure out how to write the ad.

I've been happy with my Scarebird installation on my truck. Lots of info on this site. I have better luck searching topics on Google such as "rusty hope p15d24" rather than use the search here. Be sure to do your homework and speak with the vendors before you decide.

Sweet! You need to get a Thompson machine gun to go with your car. ?