Packard Forum Index » Modification Discussion

I recently bought a '38 Packard Six. It came in boxes...at least the transmission and engine did. I'm currently putting it back together (all of the machining has been done and so forth) and I got to wondering about putting a GM transmission behind the original motor. I'm mostly a purest (at least that's been my track record). But I want to make it easier to drive but not go so far as to put in a SBC and all that kind of stuff. I'm sure someone out there has experience in this area.

I noticed that a guy in Michigan makes adapter plates for the 8 cylinder...would this also work on a 6 cylinder? Are there better options? I do have a r-ll o/d tranny, are those very a good option for this car?

many thanks,

An adapter would be pretty easy but they usually go for around a grand (800-900 plus shipping) but you would have the widest options. Finding an original 3 speed or OD trans in my experience is kind of expensive (especially if you need any repair work) and though they are strong they are not near as strong as a lot of modern transmissions. I have heard but not confirmed that a Borg Warner style transmission will bolt up to a Packard bell housing (possibly with modifying a couple holes) If this is an option you in theory would be able to bolt up a muscle car era 3 or 4 speed or a T-5 OD 5 speed out of a Mustang, Comaro, S-10, Ranger ect and they can be had for around 250 bucks give or take and are much lighter than anything Packard put out. Hope this helps and good luck.

You will need to modify the frame at the X member to fit a Packard R6,R9 or R11 to any pre 1939 Packard Six or Eight. You may be able to fit a 4.1 diff centre but the original 4.54 will simply overrev the engine if you try to keep up with traffic.
The 4.1 option would allow you to sit on 60 mph but anything over that will require an OD box.
I would suggest that any of the modern five or 6 speed boxes will only give you around a 15% overdrive, whereas the Packard OD's are a 28% overdrive
A 25% overdrive will reduce your 60 mph rpm's from around 3200 to 2400. If you already have the R11 you are nearly half way there and you can fit the 38 cane shift to the top of the box to make it appear authentic.
There is a bit of work involved but i have a 38 Six and 38 Eight with Packard od's and they work really well.
Best regards Peter Toet

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Just a note I don't know about all modern OD transmissions particularly the automatics but the T-5 has a .75OD (reduces engine speed by 25%) and if you step up to a T56 you can get OD ratios in the.50 (50% reduction in engine speed)

G'day mendocino38,
to PackardInfo.

I'll leave the technicalities to the more knowledgeable and experienced here. Instead I invite you to include your '38 Six, with or without OD or a modern transmission, in the Packard Owner's Registry here on PackardInfo!

Not sure at all about modern OD trans which are generally associated with the final gear in the trans but would be very interested to hear of any successful implants. I also like to use Packard products if possible. PT

I'm going to apologize in advance for the lengthy post.

The modern OD automatics are are computer controlled so a switch to 12v would be required (or possibly just a 12v battery and related wiring to just run the trans but I have never seen this).

The common for GM are the 700R4 which has a hard time dealing with the torque of a slightly warmed over 350 so I don't know how it would do behind a torquey Packard the final (4th gear) is .70 so about a 30% reduction in RPM its essentially a TH350 with an overdrive. You have the 4L60E which is stronger (kinda like a TH400 with an OD) It has a.696 OD which is just a hair over a 30% reduction in rpm they came in a lot of trucks and later Comaro/ Firebird stuff and I really don't see one breaking ever unless you abuse it a lot.

Then ford has the AOD these would have been in Mustangs LTD's ect. Pretty much any automatic ford cars from the 80's on. The OD is .667 so you would get about a 33% reduction in RPM I'm not super familiar with these, I know that it like its GM counterparts are electronically controlled and I have known a lot of Mustang racers who loved them and had a lot of luck but a Fox Mustang is around 2600 lbs and they don't really produce much HP and torque in stock or slightly warmed over form (most range from 210-260HP stock and go up from there).

I don't know about Chrysler OD transmissions. For a long time they didn't really have a rear wheel drive car so if you went that route you would be looking at probably a truck transmission or a very new one out of like a Charger or 300C

As for manual OD transmissions the only real viable options are the T-5 and T-56. there is a T-45 (early 4.6 mustangs) but i have heard its pretty weak but I haven't owned one first hand.

The T-5 is plentiful (cheap) and came in pretty much everything S10, Ranger, Mustang, Comaro. There are two versions a world class (WC) and a non world class (NWC) the the WC ones are stronger have better build materials. The NWC are early 80's production up till about 1985 the WC is 1986 and later till they were replaced by the T-45 in around 1996. I haven't confirmed this but word on the street is the V6 and 4cyl variants are NWC you have several gear sets with these some are quite steep (such as with a 302 Ford you are in first gear long enough to shift to second) so do your research before you buy one. The OD's range from .80 (20% reduction in RPM) to around .63 (29% RPM reduction) I have a WC T-5 in my fox body mustang and they do not like speed shifting but despite all my abuse its still holding in. With mine I can do 80 at 2000 RPM with a 3.25 rear axle ratio it will shift at 1800ish RPM but prefers to be shifted around 3500 RPM with my setup.

As way as modern manual transmissions the T-56 is king they are used in Dodge Vipers (with a .50 OD or 50% reduction in RPM) to Corvettes and all Mustangs (including the world beating Shelby GT500) the non Viper T-56's have around a .75 OD or a 25% reduction in RPM and they are quite strong the Viper is a torque monster V10 and the GT500 makes 650hp and over 600 ftlbs of torque. The down side is cost, they generally cost around 3000 dollars but I don't think you would ever brake it behind any Packard engine.

The final option is a gear vendors OD if they don't have one for your specific trans they have a universal one I believe they have several OD ratios to choose from and their staff are very good about figuring out what one is right for you. But this is a 12V only option working with a solenoid to activate the OD.

I'm sure there are dozens of other options using adapter plates and creativity but these seem like the most logical choices to me hopefully someone will find the info useful.

Good Morning everyone...

Thanks for all the good info. I'm very attracted to having the ease of an automatic, but hate to cut to cut cross members or anything...which it sounds like I would have to do if I do anything other than Packard.

Hmmm...decisions. I have a very good condition R11 with top loader and all of the pieces to activate the o/d. The fella I bought it from was a former electrical engineer in the Navy. He drew up a diagram of how to run the circuits, etc. Sounds like this is no doubt the easiest option for highway speeds.

I'll check into the 4L60E...tougher and automatic. I don't mind converting to 12v. In fact Uncommon Engineering makes a 12v one wire alternator that uses the body of an Autolite generator. Very Cool. I used one in my Hudson. That of course allows for cell phone charging and all the modern niceties.

Finally, I think the Packard Six is the perfect car for making these types of changes to. It's dressed down, affordable, but still built well and maintains plenty of Packard grace.

thanks again for the tips and advice.

-Erik

Another thing you may want to consider using a non Packard tranny is the position of the shift handle. Most modern floor shifts have the handle farther back from the front of the tranny than your 38 tranny. Just use the R11 in your 38. I put an R11 in my 38 8cyl coupe. Cutting the X frame is not a big deal. PM me if you need details.

I dont remember the name of the company but jegs/ summit sells a one wire alternator that looks like a generator as well might be worth looking into