rear end swap on a 49 Plymouth

OK fellow HAMBers... I have searched the forum and come up dry. Having never done this, I need some advice on swapping rear ends. I am stuffing a 55 Plymouth 260 Hyfire and a 5 speed into my 49 Plymouth, Big Blue (http://www.jalopyjournal.com/forum/showthread.php?t=360864). I am going to have to swap out the rear end for multiple reasons - 49 has the e-brake on the tranny, and the souped up Hyfire is putting out a few more horses/ ft-lbs than the old flat-6. I'd hate to put it all together, only to twist the ass end out of it the first time I put my foot in it! Since my 9 yo son and I are pulling this off in our garage, we're not up to doing anything on a grand scale. Are we going to be able to swap something a bit more stout in without too much fuss? I saw the rear end out of a mid-60's V8 Valiant go under a 50 Dodge (after moving the spring perches). The 8 1/4" rear isn't the stoutest... but does it have that bad a rap? Do I need to upgrade to an 8 3/4?? Dispense your wisdom upon me, oh great gurus of the HAMB!!!

 

i swaped an early dakota rear into my 51....

 

Early Camaro will bolt in. So will many others. Just wander your friendly local junkyard with a tape measure.

 

Dang... that would mate up perfectly with the Dodge Dakota 5 speed I'm gonna' stuff behind the Hyfire... maybe I shoulda' grabbed the whole darned driveline?!?!

 

I believe a B-body rear is a direct bolt-in...

 

I have one from a 69 roadrunner in my 50 dodge. you neeed to cut the spring perchs from your old rear . the plymouth uses very narrow springs.

 

84 Dart fit right in a freind,s 48 .

 

I'm a Mopar guy.....so don't be offended when I tell you the 260 Hy-Fire wont harm the rear end in your '49 Plymouth. However, you are correct that it is best to swap it because of the E-brake issue. Years ago I put '55 Dodge 270 Hemi in a '53 Plymouth (with stock tranny & rear end) and drove it for years with absolutely no problems.

Ford 8" axles come in many widths and are plenty stout for your intended powertrain and may be cheaper than some other choices and have the 5 x 4 1/2 bolt circle. Also the Mopar Corporate 8 1/4, especially under Jeep Cherokees, would also work very well and also have the 5 x 4 1/2 bolt circle. Most Cherokee 6/automatics have 3.55 ratios which are in the range suitable for the 5 spd O/D trans.

 

I am not at all offended... but the Hyfire isn't being built to be a run of the mill plant.

On a separate note - I think I found a very good source of info on different rear-end setups.

http://www.4secondsflat.com/rearendtech2.html

From this info, it looks like (on a budget) the 8 1/4" might be what I need, unless I stumble on a 8 3/4" (more gear ratios to choose from) that is complete and being offered for a good price!

Since I'm running a 5spd, what sort of gear ratio should I be looking for? I'd like a little zip off the line, but my main reasoning for the driveline swap was to get some reliable highway speed for distance and cruising. Hnstray suggests that a 3.55 would work... any other ideas? I accept any and all input!!!

 

Try working backwards...decide what rpms you want to see at your chosen cruise speed and play with the numbers. With an O/D reduction of .7 a 4.56 rear looks alot like a 3.23 at 1:1. However, double check what first gear looks like. Here is a great web link:
http://ctny.audiworld.com/mark/s4/gears/gear_calc.html

Also, check the magazine article from proartguy in this link:
http://www.jalopyjournal.com/forum/showthread.php?t=415345

Gary

 

I found an 8 3/4 rear for $200. It's a little rough looking, but I think it might work. It has a 3.55 gear in it, and it has a 489 casting number. The seller claims it's a posi, but I'm doubtful. Thoughts??

 

check the width backing plate to backing plate. you're probably looking for something 54-maybe as wide as 59 inches--depends what it came out of--ranger OK, T-bird/cougar ok full size may be too wide.

I did a swap on a 51 Plymouth a couple of years back. we used an early mustang 8 inch. it was about 53 backing plate to backing plate as I recall--and was actually a little narrow for the car, but worked great. your biggest hassle will be with the old plymouth driveshaft. spend the money up front had have a new one made--it will save countless headaches and hassles

matt

 

Thanks falcon - good thing to know on the driveshaft! I'll start budgeting for that now, rather than later. I'm looking for something about 55" from plate to plate (that's the rough consensus on here and from fellow Plym enthusiasts. Your 53" does sound a tiny bit short, but I guess it would work in a pinch. The real key seems to be in rejiggering the spring perches. Fun, fun, fun!

 

also consider brake size. I put a 67 cougar 8 inch in my 47 dodge, the brakes improved 30 to 40 per cent. The spring perches had to be moved on this one. Look for Mustang people. A lot of them are replacing their old rear axle for 8.8 axles.

 

i used diplomat brakes on my dakota rear ...lil bit bigger....used the og driveshaft with a conversion u joint...all in all cost me about 90 dolla from pickapart

 

Looks like a good deal, if the width is useable then go for it. The 489 case sports the best pinion and bearing combo and it sure looks like a sure-grip. With your Dak 5-spd the 3.55 backs down to a cruise ratio of about 2.4 or so.


.

 

Spin that ring gear around and take a look at the open spots. If you see a couple of springs, it's likely an Auburn or cone-style. My Dana style sure grip has more openings to it than that one.

 

The last bit of info I'm waiting on are the measurements (backing plate to backing plate and spring perch to spring perch) on the rear end. If they check out (+/- an inch), I'm going to go snag it this weekend, weather and time permitting!

 

I used a mid 76/78 Dodge Coronet rearend in my bro's 39 Dodge & it bolted right in. Spring pads were in the right spots, the only difference was it was about 2inches wider, but it did fit well...joe

 

Well, I think this just about broke my budget, but BOY is it sweet! I picked up an 8 3/4 rear end this morning. It's been powdercoated beautifully, fitted with a custom filler and bung (supposedly by Bill Scribner), and I got the whole shootin' match - axles, backing plates, brake drums, spring perches, U-bolts... etc. It looks great sitting on the floor in the garage, but it'll look even better under Blue! The only down side is, I'll have to move the perches and mess up some of that beautiful powdercoating.

 

it's a little late but i used a jeep cherokee rear.

 

hey pete, after you get the perches all figured out, talk to mike teenwolf. He works at a coating shop, and can get it done for you fairly cheap

 

God Bless Craigslist - I got a line on a 489-code pig with a 3.23 gear last night. It isn't posi (don't think I'll be launching Blue out of the hole any time soon), but the price is right. I may cruise up to Federal Way and take a look at it this week... assuming the photos check out.

 

Nice thread, and perfect timing for me, I,m doing the t-5 swap on my '49 over the holidays. Been looking for a rear end and this info is great,
BCT: What to you mean by "og" ?...."used the og driveshaft with a conversion u joint.." was it the correct length?

 

I think he meant the original, but may be wrong. PM him if you're still unsure. Let us know how the t-5 swap goes - be really interested to know what else is going under the hood?!? I like the looks of your '49... but must admit I have a soft place in my heart for late-40's MOPARs.

 

car is all stock under the hood, just split some manifolds last month, need to finish them up and install. Will be doing a pic by pic on the tranny install.
I,ll keep you posted.

 

I was going to hop up the flathead... until I found this, and realized Big Blue needed a heart transplant/ upgrade.

http://shadowmtkustomz.blogspot.com/

I went a little bit nuttier than SMK, opting for an oddball engine, a Dakota trans, and an 8 3/4 rear. I figure it's a good winter jigsaw puzzle for me to fit together.

I'm looking forward to seeing how the t-5 swap goes - maybe you can do a tech article on it!

 

I,d luv to RedRam it, maybe in the future. Did you ever measure your 50?
perch to perch etc, found a 8.8 from a Ranger for $75.00, 58.5" drum to drum, 39" perch to perch, I,m just not home

 

I'll go out and measure after I get the kids in bed.... You need to migrate over to P15-D24 and check out Don Coatney's handywork. He put a t-5 in his '48, and he has some great pics of the build! Check out his build - it might save you a headache or two!
http://www430.pair.com/p15d24/mopar_forum/member.php?u=2

 

49Dodgeboy....

OK...forgot to post the measurements for you the other night.
1949 Plymouth Rear Axle -
41 1/2" perch to perch (on center)
53 1/4" backing plate to backing plate

Looks like that Ford rear might be a tad bit long for your purposes.

I'll post some pics in a few minutes, after I get them off the camera.