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