Driveshaft issues with longer transmissions

brushwolf

Well Known Member
#1
When reading up on various transmission swaps I encountered the driveshaft angle issue that comes up repeatedly using a longer transmission and X frame with 2 piece driveshafts. Have seen threads where people have gone to a 1 piece driveshaft and even modified the frame center section to tolerate the angle, others where they are just using a shortened front section of driveshaft, etc. But not with a T56, so far anyway..

Have also been scrounging others pics of chassis online to see exactly how the center of the frame is constructed to see how that can be modified, if necessary.

Think the only vehicle I had in recent years with a 2 piece driveshaft is my 88 Suburban and never had issues or vibrations with it and it has probably 180k miles on it, many towing a car trailer with heavy cars on it. Of course, all the stock geometry is undisturbed in that too.

Help me understand this, those of you who have had problems with the driveshaft, or more engineering skills than I do:

The problem with the longer transmission and the original angle/plane of the motor and transmission assembly (assuming we want that to remain very close to stock), is that the longer transmission (say a T56..) puts the output shaft of the transmission lower than a stock setup. That results in an uphill angle from the rear of the transmission to the center driveshaft carrier bearing. Or not? (Assume floor is modified as necessary and transmission mount is modified to keep motor and transmission on the factory plane)

Rough measurement of the T56 including bellhousing to the very end of the output shaft is 32 inches. Measured an old GM 4 speed (think it is an early T10, iron maincase, aluminum tail housing) and a bellhousing and I come up with 22 inches and 6 1/2 inches respectively for a total length of 28 1/2 inches.

So a difference of 3 1/2 inches approximately, but IDT the original 1960 stick transmission was 22 inches from front of main case to end of output shaft, so adjust for that accordingly if there is a difference. My understanding is that there is, and the Show cars or Inland front driveshaft aftermarket piece differs by being shorter roughly the same amount.

Add the 3 1/2 inches of difference between these 2 setups and whatever difference the aftermarket shorter driveshaft front section has to the original front driveshaft section (3-4 inches?) and you now have a total of about 7? inches further back than stock at the end of the T56 output shaft.

So, judging from pics only, that seems like the transmission output shaft would be pointing quite a bit lower in the constricted center of the frame tunnel than the original (or a T10) and that just shortening the front of the driveshaft may not work as the angle of the driveshaft front to the center driveshaft bearing will be quite a bit steeper. Uphill even..

Is it possible to either lower or move the center driveshaft bearing further to the rear (shortening the rear half of the driveshaft instead), or is a one piece driveshaft and attendant frame tunnel mod's in the bottom of the frame center section the only way using the longer T56?

Never ran into this issue on any of my Ford projects. :dunno

Thanks, Mike
 
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Jeffrey Osstyn

Well Known Member
Supporting Member 3
#2
I can tell you what I have done. '63 Impala, Tremec 5 speed. In order to get the transmission in at a 3 deg. down angle (or less), had to cut the floor and raise it up about an inch. This leaves a very minimum space between the top of trans and floor, maybe 1/4" in the closest spot. This also leaves a minimum clearance for the headers to clear the lower control arm. I can not lift the trans up any more without the headers hitting the control arm. With a 2" drop on the front spindles, header to ground clearance becomes a problem, also the mufflers are tucked up as close to the floor as possible without hitting, many hours of exhaust pipe mods needed to get there! I have dragged mufflers for many miles while fine tuning this.
So, transmission up as far as it will go, I run a two piece drive shaft. Center bearing switched to solid mount so a slip yoke needed on rear shaft. The shaft out of the trans actually goes up 1 deg. to the center support bearing. I can adjust the rear shaft angle pretty much anywhere I want without a problem hitting anything. Currently running 3 deg. down. No vibrations with this setup.
As far as the frame center section goes, the u-joint on the transmission end is huge compared to the old one (saginaw). So the bracing needs to be cut away to get the joint to pass through. Tough to do neatly with the car assembled.
Have fun!
 

brushwolf

Well Known Member
#3
Floor pan replacement is in my future anyway, so I thought I would have better than usual access to do anything needed in that center driveshaft tunnel and frame area at the same time.

I am also sticking with the cast 2 1/2" larger outlet truck (?) manifolds assuming they fit the body/chassis, so maybe that will give me a little more latitude than with headers.

But, I don't want to raise the tunnel so far that carpet just won't fit, or engine angle causes radiator and fan angle issues either. Then again, it's probably easier to change the radiator angle a bit than modify the frame center.

Some older TBirds used a near horizontal engine/transmission angle with angled carb spacers to reverse out the angle cast into the production Ford intakes and get the carb level. Not sure if that is worth looking at, but with a factory intake I am guessing I would have a little leeway there too, if using aftermarket air cleaners.

Last two images aren't mine but since the car is 140 miles away, I have been scrounging added pics to get an idea of what the obstacles will be.

Thanks, Mike
 

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brushwolf

Well Known Member
#4
By referencing the holes in frame sides, or other reference point in these pirated pic's, where longitudinally does that center hanger bearing mount? Halfway thru the frame tunnel, or closer to front or back?

Thanks, Mike
 

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brushwolf

Well Known Member
#5
While the one piece floor looks really nice, I think I may be better off with what appears to be a two piece. The freight must be a whopper on that one piece.

Plus, I'll likely have to cut the replacement from the firewall to just under the front seat anyway to raise the floor tunnel, then form each side of the new half floor panel to the modified brace curvature at the tunnel, and fab up the center (which will likely then have a gap between the two new half floors).

Tack it in with the motor and transmission sitting on the mounts, so I know it has just enough clearance for the T56 all the way to the firewall. Likely that my tunnel is intact on the top toward firewall, so maybe I can retain part of the center too and raise it up to fill any gap between the tops of the new floor sections. If not, then use new sheet steel to fill the gap.

I anticipate cutting the front floor brace half way up the center rise on each side and welding an inch+ piece back in so it will be similar to factory, but slightly taller. (Which I suppose will also make it likely the bench seat frame might need to be tweaked a little also, but will cross that bridge when I come to it..)

Anyone know who sells the two piece floor pan shown in pic 2? I only seem to be able to find panel listings for the foot wells and toe boards separately, or else the whole floor...

Thanks, Mike
 

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Jim Sullivan

Well Known Member
Supporting Member 7
#6
I guess it depends on the year car you're working on, I probably read it somewhere and don't remember. Hubbard's carries the Dynacorn half floors. I believe Cars may carry their own half and full floors. Classic Industries carries floor pans also.
 

brushwolf

Well Known Member
#7
1960 Impala 2 door hardtop. Have found other years with some suppliers. Lots of companies selling the full floor pan, but none the half floors...

Thanks, Mike
 
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brushwolf

Well Known Member
#9
That's what I was afraid of, since I hadn't found any ads listing half floors and the half floor pics I had saved looked a little different. Guess I will have to watch the full floor prices and how far away they are. Or maybe there are vendors that will bring them to Back to the 50's car show in St. Paul this summer. Don't want a 20 piece floor..

Titled car was only $1500 anyway (plus my hauling it from Arkansas), so compared to money spent on motors and transmissions already, it easily warrants the floor replacement cost in my book. Besides, it is one of my two all-time favorite cars, so it will be worth it to me. :)

H&H was running a sale on the full floor for like $630 not including shipping, however I don't know who makes them and they are sold out. I suspect a lot of the vendors get them from the same source, but not all do and there is some junk out there too.. The prices seem to vary a few hundred between vendors as well, but maybe they pad the freight charges on the lower list price sellers.

Thanks, Mike
 
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425/409ER

Well Known Member
#10
I went through that crap with my 68 Firebird and a T56. It's hell getting those angles right, even after that I still had vibration, found out the shortened driveshaft was slightly bent. Got a new one let everything else the same and car drive real nice. I have state before I went the 1 piece route on out 63 and drives so much nicer than it ever did with the last combo. I sure do kick myself for getting rid of the 409 P/G and that driveshaft, the car was the smoothest ride ever. Listen to my buddies that "you need a turbo 350 in that car", needless to say, he is not my friend anymore. I just let him screw up other peoples cars now.
 

pvs409

Well Known Member
Supporting Member 6
#11
Cars Inc in Michigan who sells jig welded floors with all the factory braces (great quality -we bought one for a 62 Chevy convertible -car is done......) . They come to Back to the Fifies every year I have been there, I ordered parts for 10 % at the show that they shipped to me.
Our complete jig welded floor pan with all the braces cost $ 145 truck freight to Western Iowa(at the Nebraska border) from Michigan.

Overseas floors I would not trust for quality. The price difference was only about $ 200 more for the overseas floor not worth it for the fit....

I just checked for the 59 and 60 this is what I found in there catalog(their catalog is 1" thick with lots of pictures) I think its free.

they sell the front section of the 59-60 floor pan (part # 15928) -it says its a one piece stamped full floor pan (there is a picture in their catalog) -it says to add the under back seat floor pans sold separately and to add the braces. I am sure they could send you a picture.
https://carsinc.com/catalogsearch/result/?q=15928

Pictures of the floor pan we got for the 62 convertible (transferring seat brackets, seat belt brackets,etc
and installed in the car
Paul
P1030448_tn.jpg
P1030331_tn.jpg
 

brushwolf

Well Known Member
#12
I went through that crap with my 68 Firebird and a T56. It's hell getting those angles right, even after that I still had vibration, found out the shortened driveshaft was slightly bent. Got a new one let everything else the same and car drive real nice. I have state before I went the 1 piece route on out 63 and drives so much nicer than it ever did with the last combo. I sure do kick myself for getting rid of the 409 P/G and that driveshaft, the car was the smoothest ride ever. Listen to my buddies that "you need a turbo 350 in that car", needless to say, he is not my friend anymore. I just let him screw up other peoples cars now.
What kind of mod's did you have to do at the frame center to accommodate the 1 piece on the 63?

Thanks, Mike
 

brushwolf

Well Known Member
#13
PVS409,

That is a pretty exhaustive online catalog all right. All kinds of goodies in there including seat foam I will need and front floor brace if I need it. I have bookmarked that online catalog for reference.

Will also check out the paper catalog availability since pics are helpful and either they haven't got many of pics up, or my browser won't bring them up.

Thanks, Mike
 

425/409ER

Well Known Member
#14
What kind of mod's did you have to do at the frame center to accommodate the 1 piece on the 63?

Thanks, Mike
In the back you have to cut about a foot (maybe less) out of the bottom plate of the frame, you also have to eliminate the e-brake brackets. You also need to reroute the fuel line to the outside of the frame, which one should do anyway. In the front opening as you look through the hole in the front where the driveshaft goes through all that area need to be opened up. Some people chose to as a new piece of curved steel plate to the bottom of the rear potion that is cut out but I just reused part of an old driveshaft loop from a race car, welded both sides to the frame then you can bolt and unbolt the piece in the middle if you need to remove the driveshaft. You can do almost everything with a sawsall which is what I used. You will need to drop the rear axle down to put in the new 1 piece driveshaft. For me it was worth all the trouble. I am sure other will elaborate and there a bunch of threads on here for you to read to change it over. Nice thing for you is that with the T56, it makes the driveshaft even shorter than mine so you might be able to use a 3" tube, but mine used a turbo 350 so I elected to use a 3.5" driveshaft. One thing for sure, when you get done you're going to like driving the car in 5th and 6th gear. I know in my bird I sure do love going 80mph at 1900rpm.
 

pvs409

Well Known Member
Supporting Member 6
#15
PVS409,

That is a pretty exhaustive online catalog all right. All kinds of goodies in there including seat foam I will need and front floor brace if I need it. I have bookmarked that online catalog for reference.

Will also check out the paper catalog availability since pics are helpful and either they haven't got many of pics up, or my browser won't bring them up.

Thanks, Mike
If you buy from Cars Inc at Christmas they normally have a 10 % discount.
I ask for Joe Z.
 

pvs409

Well Known Member
Supporting Member 6
#16
In addition they have a $ 25 gift certificate for every $500 plus the 10 %
I think Joe would send you a catalog for free. I stop there about once a year when we are in Michigan and pick up catalogs for free.
Paul
 

ragtp66

Well Known Member
#17
Cars Inc Gave me 10% discount on all parts ordered prior to the show (Spring Jefferson) as well as they brought it to the show so no shipping charge and i didn't have to pay sales tax at the time because it was being delivered to a state that they did not have a physical location in. The tax laws have changed and some companies are now collecting the tax regardless if they have a brick and mortar store. Just call it never hurts to ask. On sheetmetal I always ask if they have any open box or scratch and dent stuff for a discount. I figure most of the time stuff gets dinged up in shipping anyway so if I can save more upfront I will take it.
 

303Radar

Well Known Member
Supporting Member 2
#18
Whether you order through Cars Inc or Summit, the only manufacturer I have found for 59 & 60 floor and body panels is Sherman.
On the Sherman page listing for 1960 Impala, they even list the part number to order through Cars Inc.
https://www.shermanparts.com/ecat/base/dropdowns.php?make=Chevrolet&model=Impala&year=1960
Looks like Sherman and Cars Inc work closely together.
If you're able pick up at either a Sherman, Cars Inc or Summit store/location, I can't imagine any taxes would be more than the freight cost on a whole floor setup.
 

brushwolf

Well Known Member
#19
Yep, I noticed that the Cars part reference numbers were on the Sherman parts listings. Wasn't sure whether that meant Sherman made the parts for Cars, or vice-versa... Looks kind of like what EMS does with marketing their Ford panels through lots of different resellers.

Not previously familiar with Sherman, Cars,Inc, or Classic and we have an Auto City Classic 20 miles from me who does a lot on EBay, but also have a physical store here near here. Lotsa glass all years, lots and lots of 58 Chev stuff, lotsa 57-58 Ford stuff, lotsa disk brake conversions, radiators, etc.

So, wasn't sure the "Classic" previously mentioned was that company or another one. Appears to be another, so have now gone thru both of those companies online listings. Just looked thru the CARS, Inc stuff early this morning too and requested a paper catalog also.

Yes, the sales tax considerations can add roughly a hundred to the parts cost and the freight possibly a couple hundred more, so avoiding at least one of those leaves the difference for more productive uses. Also as mentioned, some sellers are now charging sales tax even for states they have no presence in, but not all are yet. So, pays to ask questions I guess..

As PVS 409 says, they are running 10% off Christmas Special at Cars now and also adding a $25 coupon for future purchases for every $500 spent, so I may need to go drag myself out to the car (140 miles away) and take a closer look at floor braces and inner rockers and see if I can get in an order before Christmas.

Hate it when I buy parts and end up not needing some of them after all, though sometimes it's easier to just order everything you think may likely need replacement and be done with that aspect of it. Not sure if my shoulder is ready to go under cars just yet though..

Thanks, Mike
 

brushwolf

Well Known Member
#20
Kind of got off the original topic there, but one thing leads to another.. Gonna take floor mod's to accommodate the T56, likely driveshaft angle issues which should probably be dealt with while the floor pans are out anyway, then put the floor back together, so what is available in floor parts and where will those parts come from? Probably should have started this posting series on my project thread, but oh well...

Thanks for all the input.
Mike