4-speed in an old Mopar
#1
Lexus Test Driver
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4-speed in an old Mopar
We're getting sidetracked here but you guys are talking about interesting things to me. I recently was given a 1972 Plymouth Scamp. I did a 140 mile (one way) road trip with it, and the trans is a 727 (360 engine). It's turning about 3,000 rpm at 60 mph. And the trans slips out of gear when stopped. Would a 46RE or 47RE fit without major reconstruction? This car could use an overdrive ... big time.
Jason
Jason
Instead of the 46RE, you'd be better off using a 46RH because those are hydraulic, not electronic. The fourth gear bit is literally bolted on to the tail of the 727 (for all intents and purposes), so you'd have to shorten the driveshaft, but I think that's it. I know someone has done this on a Mopar forum/board, somewhere. I mean, they must have.
My Grand Cherokee has the same 360 (5.9L), and likely similar gearing, and at 70 MPH, I think I'm turning over barely 2K. I'll pay attention, next time.
Torque is your friend. :-P
Do you know how the pumpkin is geared on this Scamp/Valiant (A-body)? I mean, it could be you have 4.10 gears, and yeah, that'll kill your MPG at 70 MPH!
Found this place: http://www.mopar1.us/875.html With any luck, you'll have the desirable 8 3/4 diff, because there's a ton of gears available for it.
Wait, you found a '72 with a 360 in it?! You sure it's not a 340, 'cause that was the largest OEM motor they offered in the A-body in '72. Even so, mmmmm, a 340 and a six-pack...mmmmmm.
edit: Something occurred to me on the way in to work (yeah, Sa-Su, 8A-8P and M-Tu, 6A-2P), overdrive is going to help, sure, but if you can put in a lockup converter, there's another whole bunch of piston energy not being wasted in the converter's fluid coupling.
Thanks, mmarshall...I wasn't sure if the 360 was ever in the Scamp, but I was certain it came in at least one A-body (which may also be the onset of old age), so I'm glad you brought that up. Thinking about it some more, I believe the best you could do was the 318.
It's kind of a trip how, in the Barracuda/Challenger, you could have anything from a 225 c.i.d. slant six to a 440.
Last edited by mckellyb; 04-08-17 at 08:17 AM.
#2
Lexus Fanatic
I wouldn't swear to it, but, from what I remember (and I grew up with those cars)....the 340 (which was actually a bored-out 318) only went into the Plymouth Duster, Dodge Demon, and Dodge Dart Swinger coupes, not the Plymouth Valiant Scamp. As far as the 1972 model-year, maybe the OP is is refering to a retro-fitted 360.
The 340 also went into the 1970+ Plymouth Barracuda/Dodge Challenger, and later versions of the Plymouth Road Runner, but those were separate lines of vehicles from the Valiant/Dart line.
Last edited by mmarshall; 04-08-17 at 06:44 AM.
#3
Lexus Fanatic
Yes, correct. To say it is just the bore is an oversimplification. The 340's output, though, was quite impressive for its size....obviously more than the official 275 HP claimed for it.
#4
Former Sponsor
He and I remained friends, he was my mentor at my first (engineering) job. He's the smartest dude I've ever known. He put his house up for sale about 5 years ago and asked me if I wanted to buy the Scamp. At that time, I had no garage space. His house finally sold (it took years, but he didn't care, he wasn't hurting to sell it). But when the sale finally happened, it happened in a hurry. About 6 months ago, he had to move the car out of it's garage and sat it outside. He then called me again and asked me if I wanted to buy the car. I said, now that I have space, I have a HELOC I'm trying to pay off, and the wife won't like me buying a car instead of putting that money toward the HELOC. A couple weeks later he called me and said, "why don't you just take the car?" How could I say no?
I took the car home about 1 month ago. Since then I've given it a lot of TLC and replaced the heater core. It wasn't roadable at the time (mainly because the brakes weren't working), but now it is. And I've been driving it, even drove it into Atlanta yesterday. The engine is a 360, out of some larger 1975 model, he couldn't remember exactly. The engine was built by Herb McCandless in about 1995 or 1996 per my friends direction. It has a mild cam, and is a rather conservative build. My buddy never wanted a pure drag car that only ran well at high rpm. It idles well, with just a hint of cam aggression (lope) at idle. It runs great on the street. The 906 (I think it was) transmission was swapped for a 727, and it does have the 8-3/4" rear end. The original engine was a 318. Here's a link to some pictures of the car when I went to pick it up, then when I got it home and put it up on auto-dollies. https://drive.google.com/drive/folde...UFUa01UdjBhZDg
I found a 47RH (rebuilt) on ebay for like $1,500. Sounds like a good combo for this car. I could keep the acceleration provided by gear 1, 2 and 3 (which was my buddy's original intent), and have an 0.68 overdrive for better highway cruising. The best of both worlds, if... Since my post on the other thread, I read up about Chrysler transmissions. 4 is for 4 speed. 7 is like a duty rating (between 1 and 9 I think), R is for rear wheel drive, and H is for hydraulic. So yes, a 47RH would work if it would bolt on (that's the *IF*). I see I would have to shorten the driveshaft.
But what about bolting to the engine? And fit to the firewall? Any problems there?
Jason Oliver
Last edited by Oliver Enterprises; 04-10-17 at 10:42 AM.
#5
Lexus Test Driver
Thread Starter
I think, a 46RH will bolt up because it's literally a 727 with an OD thrown on the back of it. Don't know about the 47, but that's likely out of a pickup. Even if it doesn't, I'd put money on there being a relatively inexpensive adapter.
Between the overdrive and a locking converter, you'll be amazed at the MPG and engine speed change.
I doubt any of the body/chassis interferes. If it does...the solution is a hammer. :-P
Between the overdrive and a locking converter, you'll be amazed at the MPG and engine speed change.
I doubt any of the body/chassis interferes. If it does...the solution is a hammer. :-P
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