I'm getting ready to install a Jumbo Giant accessory transmission. It came without any installation hardware, though I've earlier found the special coupler in the front that tends to fall off when you take it out.
Now I'm checking what type of screws I need. Only one screw from the Ford U-joint bolt kit seems to fit, at the rear lower left. In the front lower left position there's not enough room to get a long enough screw in place, so I guess a stud was used there originally. The other fasteners seems to have been long bolts going all the way through the trans?
Are 3/8" UNF bolts available 10.5" long or would threaded rod be strong enough in this application?
There are two 3/8" threads going into the U-joint ball area from below in the rear, guess it's for a supporting crossmember?
Does anyone know what the original support looked like?
Roger- a Jumbo came in a TT truck that I once owned. Personally, I would not install a Jumbo in a car for this reason- we could only shift it from low to high while moving or stopped. Going from high to low was suicidal because the gears would never mesh and the trans would hang in neutral, hence- no brakes. Downshifting req'd a full stop.
Now, it is possible that mine was defective. If so, someone will surely chime in with their view.
I have some information on the Jumbo Giant that may be useful to you. Unfortunately this site will not accept (I think) a pdf attachment so I will send via email. However I would like to share this info with the forum...perhaps someone can clue me on posting it. Too much to scan.
I'm aware old unsynchronized transmissions doesn't shift easy so I think I'll just use the direct and overdrive occasionally, the Ford planetary is so much easier to handle, so I wonder why they put a reverse in the Jumbo too?
Of course I'm adding extra wheel brakes too - that's essential when mounting an accessory trans that can get in neutral - and they all can..
Thanks John McGinnis, any info is welcome My e-mail is in my profile.
Maybe you can save the Pdf pages in another format easiest if you have a snipping tool in your computer?
Most, not all, Jumbo Giant transmissions did have reverse. Jumbo also made smaller two speed transmissions that of course did not have reverse.
I can't get to where my Jumbo Giant transmissions are stored, so I am going from memory (more and more dangerous) and your photo. If I recall correctly, they do require a short stud on the lower left (right?) pan location. The rear of the JG should work with a regular bolt put in from the rear end side for that same lower left (right?) position. Again, IF I recall correctly, the other three bolt positions use long studs that go through the length of the JG case and connect the rear end/U-joint coupling to the T engine/trans all in once. One of the jGs I bought several years ago had been removed from a T by use of a cutting torch. They had done a wonderful job of forcing one of the slag encrusted studs into the JG case and getting it very well stuck. I did manage to get it apart. One or two of them I think go through the gear case where the grease and gears are.
I have never seen a known correct JG to chassis frame brace, so I cannot help much with that.
I have known several people running Jumbo Giant transmissions that claim they have no difficulty shifting on the drive. That is an art and a skill that some people handle with ease. Other people will never be able to do so. There is nothing wrong with not being able to shift these things on the fly. It is just one of those things that some people can do easily, and others cannot do so well.
Good luck with your JG tranny, Roger K! Someday I hope to put mine into a car.
Drive carefully, and enjoy, W2
"Are 3/8" UNF bolts available 10.5" long or would threaded rod be strong enough in this application?"
Ifn you can't find long bolts 3/8" UNF threaded rod is available in grade 8. At least around here.
Yep, good quality threaded rod is what I need. Most threaded rod I find in the stores here seems very soft.
There is space enough for M10x280 bolts through the upper holes - that might be easier to find over here, though some checking on the net didn't give an obvious source, most wants to sell me a box of 25 while I only need 2.. Well, they'll turn up.
I've snipped John McGinnis' PDF, it's a good article on several aux trans options by Louis P. Baudoin - let's see if it'll be readable:
Thanks again, John - I'll post the rest of the article in another recent aux trans thread.
"Yep, good quality threaded rod is what I need. Most threaded rod I find in the stores here seems very soft."
Grade 8 UNF all thread rod is available here in the bolt supply houses. I could send you a couple of 12" pieces w/nuts if need be.
Thanks Ken, but I found a supplier in England that'll send me some 3/8" threaded rod and one in Germany that sells a couple of M10x280. It's been 40 years since Volvo stopped using their last inch size screws in the driveline so UNF is hard to find over the counter here, but thanks to the net it's easier to get now than back in the 70's - 80's
Link to the other thread with the copy of an article mentioned (in case the threads become separated later).
Test fitting the Jumbo.. Hey, how is the hand brake cross shaft supposed to be rearranged with a Jumbo in place?
No way to get the car out of neutral, the cross shaft touches the auxillary trans when I try. With more bend so it can go under the Jumbo, it'll flex too much so the RH emergency brake wouldn't be as strong as the LH brake. Something else needed - who has a Jumbo in his car or truck?
What does it look like?
Seems like this should be a problem also with the Aluminum Warford...and Layne. Cast Iron Warford is OK because of the front U-joint extension.
Roger you are missing the spacer and special joint.
Scroll down to what Wayne Sheldon is saying. That would make sense since you need an extra bit of space for the handbrake to work.
How long is the input shaft from the Jumbo? Could you make a 1 or even 2 inch spacer to move Jumbo back? Then handbrake would work with no modification.
I've read the Jumbo brochure before but I missed this info.. They actually included a special brake cross shaft when buying a Jumbo transmission, so it's not like I'm missing any spacer - the Jumbo Oldham style coupler fits inside the Ford ball cap.
Now, what did the special Jumbo brake cross shaft look like? Some heavy gauge fabrication to do - and that's one of the fun parts of fixing old cars
There is an Oldham coupling shown in that article/drawing of the Jumbo Giant. Looks like something to make if you don't have one. Curious about that special brake shaft. Someone must know about it.
Hey Roger, just an idea: how much room is there between the cross shaft and the Ford transmission pan when you pull the brake all the way back?
My thought being - what if you just adjust the cam forward so that you are in high gear with the lever where it is now in your picture? Then you'd come a bit past vertical for neutral, then further past that for e-brakes. There may just not be enough travel for it to work. Just spit-ballin'.
I have a couple Jumbo Giants, and had wondered about the cross shaft. I have not yet had one installed in a T. Years ago, I had a Heavy duty Muncie. It needed a special cross shaft. I was surprised when I put the smaller Muncie in my current boat-tail speedster in that the standard brake cross shaft worked just fine without any special fitting or modifications. I didn't think that there was that much difference in the front mounting between the larger and smaller Muncie transmissions.
Unfortunately, I do not have any pictures of that modified cross shaft. Basically, it needed about three inches added to the "U", and the "U" rotated forward like Seth suggested.
I did a cut and weld for that one of mine. I think starting with a good piece of appropriate size steel rod and bending it would be easier.
That steel rod is SERIOUS stuff Wayne =)
I bought a 3 foot piece the same diameter at the hardware store when I was moving my handbrake outside the body on my speedster. That stuff is only getting bent if you have some kind of machine.
Or a large acetylene torch! Yeah, you ain't gonna make all those bends cold over the trailer tongue like I usually use.
I can't believe that there are no Jumbo installations that show the details of the brake shaft.
This site offers a movie of a TT for sale that has a Jumbo, maybe you'll get lucky and they'll show the cross shaft.
Or, maybe this document might have something:
Thanks all and especially Mark - didn't think of checking Amazon, they do offer an amazing amount of older litterature
One of the example pages shows both the supporting crossmember for the rear of the trans and the special brake cross shaft. The center U-bend doesn't appear as enormous as I would have expected if the cross shaft took the whole turn around the bottom of the trans, so maybe it just have to clear the axle boss in the front - then with some repositioning of the clutch cam as Seth suggests maybe it'll work?
Still interested in a picture of the underside of a car or truck with a Jumbo if anyone has easy access to one. The Volocars site wants $75 for a video of their truck for sale.. I'm not buying that ;)
Notice on that pdf that I sent you...it gave a design for the support bracket.
Thanks John, I saw the suggestion for a supporting crossmember - it's just that it's Mr Baudoin's idea on how to make the support, I'm also interested in how it was done originally and the experiences from the group here, then I'll make my own conclusions
Odd that so few seems to have real life experiences with Jumbo transmissions, though? Are they so rare compared to Warfords and Ruckstells?