MTFCA Forum

Helping a friend with a new purchase. TT and it has a Jumbo ppoverdrive. Seems to function properly. Need to change fluid. Not sure how full to fill and what oil. 600 W, 80/90 or ??? Anyone have one and could give some advise. Thanks

Decent auxiliary transmission. I don’t know the fill level for a Jumbo but with a Muncie or original Warford about 1/3 of the case with 85-140 is what I’ve seen. I’ve also seen the results of over filling sloshing out of the relief orifice. I’d encourage you to use a climbing oil product in addition. “ In 1923 the Price-Hollister company in Illinois began building the Jumbo transmission. Like the Muncie, this was a selective sliding gear transmission and in conjunction with the Model T Ford transmission, also produced 7 forward speeds and five reverse. Transmissions were provided for both the car and truck market, but in 1924, the company began producing the Jumbo Giant. This was basically a "beefed" up version of the Jumbo transmission, specifically built for the truck owner.” Attached is information you may need for you friend courtesy of Frank Brandi

Best John

I have never seen or heard of a "Jumbo Giant" transmission; I don't know whether it's great or not, but they weren't real creative with the redundant name for it.

There is a filler plug on the other side. Its about 1/3 up from the bottom. fill to the level below the threads.
I prefer the 600wt model A grease. There is a ball end with flats on the shift lever that wears. Build it back up to tighten the shift pattern. There is a divider plate between the 2 shift forks, make sure its there. It eliminates the possibility of shifting both forks @ the same time.
Quality transmissions IMO. Typically Hyatt bearings in the cluster & main shaft, (but I did disassemble one with bronze bushings in the cluster.)
They should be checked for wear & tightness of the cages.

Difference is the Giant version (333) of the Jumbo has 3 speeds. The Jumbo (B-C) only 2 speeds.

What is the value of a Jumbo Giant trans? I need to go look @ one for a friend & make recommendations, are they worth more or less than a
Muncie or a Warford? Sorry for the interruption.
Craig.

RE the adapter: I have to go check mine but pretty sure there is a spring that fits in the square hole that presses it away from the output shaft and helps keep it engaged with the tabbed part on the transmission but is not shown in above drawing.

Mark Gregush wrote: ↑

Tue Sep 17, 2024 11:50 am

RE the adapter: I have to go check mine but pretty sure there is a spring that fits in the square hole that presses it away from the output shaft and helps keep it engaged with the tabbed part on the transmission but is not shown in above drawing.

Correct.

There is about a 3/8" hole in the drive square for a spring that would press against the plug inside the output shaft. Not keen on that thinking.
The spring could loosen the plug, however it cant move far, backed by the clutch spring retainer cup pin.

The coupling shows how to make a usable part, its not showing an original part. The original nose is one piece forged, not welded.

As far as value. The same price range as I see for warfords or muncies, but they are less common.
I have paid $50 to $300 depending on the all important condition of all the gears & completeness.
Original couplers are super rare. They fell out & got lost when removing the transmission.

speedytinc wrote: ↑

Tue Sep 17, 2024 12:17 pm

Mark Gregush wrote: ↑

Tue Sep 17, 2024 11:50 am

RE the adapter: I have to go check mine but pretty sure there is a spring that fits in the square hole that presses it away from the output shaft and helps keep it engaged with the tabbed part on the transmission but is not shown in above drawing.

Correct.

There is about a 3/8" hole in the drive square for a spring that would press against the plug inside the output shaft. Not keen on that thinking.
The spring could loosen the plug, however it cant move far, backed by the clutch spring retainer cup pin.

The coupling shows how to make a usable part, its not showing an original part. The original nose is one piece forged, not welded.

As far as value. The same price range as I see for warfords or muncies, but they are less common.
I have paid $50 to $300 depending on the all important condition of all the gears & completeness.
Original couplers are super rare. They fell out & got lost when removing the transmission.

I way overpaid on the last one ($400) I got looking at the gears from the outside but did get an original coupler. When I took it apart, the counter shaft bearings fell out like rain dropping in the cleaning pan. The other one I have, the bearings in the counter shaft had been replaced by brass bushings which were worn and spinning in the counter shaft housing.