Dodge Camper Van w/318- switching 3-Speed to Overdrive transmission?

[Curtis336]

Hi all. This is my first time posting here. But it seems like the kind of place where I could get some good advice.

I recently bought a Dodge camper van with a 3-speed in it. And I'm curious about what is involved in putting in an overdrive transmission.

It seems like the three speed isn't going to be great for long hauls, at higher speeds.

And if I want to cruise at 70 miles an hour for a cross country trip, do I also need to replace the rear end?

Currently has a two barrel, which is not very responsive after 50 mph. I would like to upgrade the rig so it responds to gas, and cruises nicely.

I know the engine has plenty of power, but right now it feels like a laggard and I'm not sure if it's simply carburetion , or a combination of carburetion, and gearing in the rear end.

I guess my biggest question is is this a simple process of plug and play? Or is it going to require a bunch of modification.

 

[junkyardhero]

3spd manual or automatic? upgrade to a manual or automatic OD transmission?

what engine/rear end does it currently have?

 

[RustyRatRod]

Going on the assumption you have a 3 speed automatic......

The OD will probably answer all of your concerns. I don't think I'd worry about the rear gear "yet" and you might not need to. I feel sure that thing has a 727 in it now and the OD counterpart to that is the A518. You'll need to shorten the drive shaft, I believe and you may need to work something up with the transmission mount.....I am not 100% on that, it might be in the same location. But as far as room for the larger OD transmission, I believe you have enough without modifying the body like we do on our little A bodies. I'm sure some of these guys can fill in the blanks. We have lots of sharp people here.

 

[rumblefish360]

Hi all. This is my first time posting here. But it seems like the kind of place where I could get some good advice.

I recently bought a Dodge camper van with a 3-speed in it. And I'm curious about what is involved in putting in an overdrive transmission.

The Chrysler OD automatic transmission is a little longer & bulky at the tail shaft. The support fins or struts can be ground off or some hammer use on the sheet metal will be needed to clear an install. The driveshaft will need to be shortened so a tape measure will be needed and measured to how the shop wants it done. Shops vary with their instructions on this, so contact a shop.
The rear mount of the transmission is in a different location. USCartool (.com) has a long lead time on a modified transmission cross member that is a bolt in and uses a GM rubber mount. This is the east button to press for this swap. IF you can weld, or know someone, fabrication is t truly hard to make your own. The mount is moved further rear wards.

It seems like the three speed isn't going to be great for long hauls, at higher speeds.

Have you tried it and seen where the rpm’s are at while at speed?

And if I want to cruise at 70 miles an hour for a cross country trip, do I also need to replace the rear end?

No. The 8-1/4 year s up to task strength wise.

Currently has a two barrel, which is not very responsive after 50 mph. I would like to upgrade the rig so it responds to gas, and cruises nicely.

The cheapest route is a used (but make sure it’s in good shape) intake manifold like a factory 4bbl unit or an Edelbrock or Weiand intake. I like new carbs over used one unless there very lightly used. A 600 cfm carb will do you fine. I like the Carter/Edelbrock carbs for the jet it and forget it ability. Also advance your timing up to help wake it up in power and some mileage will also come with it.
I don’t know if headers are part of the plan but with or without headers, a dual exhaust is power and mileage. So is a multi spark ignition. Open up an our plug gap until power falls off. Start at a .050 plug gap.

I know the engine has plenty of power, but right now it feels like a laggard and I'm not sure if it's simply carburetion , or a combination of carburetion, and gearing in the rear end.

On the rear end gearing, know what you have now and see how the vehicle responds to the OD trans swap first. Also install a tachometer to know your cruise rpm. To figure out your final drive ratio with the OD trans, multiply the OD ratio (normally .69 IIRC) with the gear ratio.

I guess my biggest question is is this a simple process of plug and play? Or is it going to require a bunch of modification.

Just the transmission mount can be a PIA to build if USCartool doesn’t have one for your build time frame. If you can wait for it, great. If you need it now, weld up your own.

The one item of note to understand is the move to a 4bbl carb will need the trans kick down linkage modified or use a Lokar or like cable for proper transmission operation. This must be done or the transmission will not have the proper line pressure to feed it fluid. This will kill your transmission in about 10 miles if it is not done.

 

[JDMopar]

Look for a 46RH, or as it's more commonly called, a 518 transmission that was used in Dodge trucks and vans up to 1995. They can be easily controlled with the kit from PATC, to make it shift into lockup and OD. The later 46RE's are pretty much the same trans, but it costs a lot more to make them shift because they are electronically controlled instead of hydraulically controlled like the RH version. You should look for a transmission crossmember and mount from any B van that had an OD trans from 90- 2000? something. Any of the real late ones would have had a 5.2 or 5.9 Magnum motor. It might even be a bolt in, but I'm not sure? Spend the money for a good heavy duty torque converter, and if there is such a thing...a HD front pump. There's a couple of really good transmission guys on here that know their stuff, so maybe one of them will chime in.

 

[rumblefish360]

@JDMopar - Why would he need a HD torque converter and even more so, a front pump when the transmission mentioned is in an as heavy if not heavy vehicle designed for heavier loads and towing capacity?
Seems like a waste of money to upgrade something that does t need it.

If the transmission came from a 5.9, he would simply need the flex plate to bolt up to the engine making it a bolt in. Good tip on the trans mount to acquire as well.

@Curtis336

I was also thinking. On my ‘79 Magnum, there was a factory trans cooler installed. The car was just a 360-2bbl when new. Why it came with it, IDK. But any cooler is a good thing IMO. Keeping the trans fluid cooler longer on any road trip is a plus helping extend the transmission life and improve reliability.

 

[408 swinger]

With that being a camper van, it's probably on tbe heavier chassis. Meaning eight lug wheels and a Dana 60 rear. Im sure the RPM is up there, as most of those I've seen have a 4.10 gear.

 

[JDMopar]

@rumblefish360 He needs a better torque converter because the ones that came in 518's were the weak link of the whole operation. We had a 92 Dodge perversion van with a 5.2 Magnum and a 518. Really nice van, and we never dogged it. One day the torque converter took a dump and took out the pump. My transmission guy at the time said it was a cat & mouse game between those 2 parts as to who was going to destroy the other one first. That was YEARS ago. I just had a 545RFE rebuilt at a reputable shop and told them the same thing I just said above and their first question was did we upgrade to the better aftermarket converter and a better front pump? We had in fact done that at the guys suggestion who rebuilt the 518 years ago, and these guys a while back said that's the right thing to do anytime you rebuild a 518 (46RH). I'm not a transmission guy, but these 2 guys who don't know each other, and both are great at their trade recommended the same thing. As far as the flex plate goes, that does matter on a Magnum motor. An LA flex plate for a 518 equipped motor can be ordered in either symmetrical or asymmetrical bolt pattern at the torque converter to flex plate bolts.

 

[rumblefish360]

@JDMopar Thanks! Excellent information.

 

[barracuda-67]

@Curtis336 -
Is this a B200, or a B300 van?
(The B200 has 5 lug wheels, the B300 has 8 lug wheels and a super heavy-duty full-floating rear axle.)

I believe your van is a 1974, correct?

Is it the 318 engine with the 2 barrel carburetor?

I had a B200 van and a B300 camper top van. Both had 318 engines with a 2 bbl carb.

Things I always wanted to try for improving gas mileage, but never could do these:
* an overdrive unit. I'm convinced you are on the right track pursuing one. It should also make your drive quieter
* an electric fan. That radiator gets plenty of cooling at highway speed. Plus eliminating a heavy rotating fan blade might make the water pump last longer (all fans have some minor imbalance to them).
* synthetic gear lube for the differential
* different intake manifold
* headers (but they will sound different)

Best luck!

 

[rumblefish360]

@Curtis336 -
Is this a B200, or a B300 van?
(The B200 has 5 lug wheels, the B300 has 8 lug wheels and a super heavy-duty full-floating rear axle.)

Good to know!

Things I always wanted to try for improving gas mileage, but never could do these:
* an overdrive unit. I'm convinced you are on the right track pursuing one. It should also make your drive quieter
* an electric fan. That radiator gets plenty of cooling at highway speed. Plus eliminating a heavy rotating fan blade might make the water pump last longer (all fans have some minor imbalance to them).
* synthetic gear lube for the differential
* different intake manifold
* headers (but they will sound different)

Best luck!

Of the above, I didn’t notice a mileage increase with the synthetic gear oil. That is not to say it was there. It’s more likely to be proven under a test setting rather than various driving conditions ranging from rush hour traffic to the mountain hills and the flats of Florida.

I believe there would be power and mileage from an electric fan, but I never tested that.
I feel headers will give more mileage, I haven’t proved that to myself ether.
A different intake will improve mileage because the new 4bbl carb to be used will probably have smaller primaries than the two barrel. It’s not always the case. But the engine will like the better flowing aluminum intake will take advantage it.
Ignition is the other biggies.

Between a top notch and dialed in ignition coupled with better breathing in and out, most any vehicle will respond favorably. The hard part is having it show up on a heavy vehicle.

 

[C130 Chief]

I would go looking for a 46RE from a 5.9 Magnum truck, and swap the fuel injected 5.9 Magnum with it. You'll gain some gas mileage and a considerable amount of power for the cost of a brand new carburetor and intake manifold.