9" rear in a jailbar truck

GB SISSON

GB SISSON

Well-known member
I have been reading a thread tonight that goes into quite a discussion about the problematic axles in a banjo rear end. I have read tales of sphincters tightening as nuts are twisted, wheels with drums flying into oncoming traffic, threads stripping, cracks appearing, keys shearing and then going through it all again if you'd like to check out your brakes...
Ever since I built and installed a 276 flathead mated to a T-5 in my truck based woodie wagon I have been thinking about completing this powertrain 'upgrade' with a 9" 4:11 rear from a '57-'72 Ford 1/2 ton pickup. IIRC this is a simple and direct 'bolt in' to my jailbar springs and driveshaft. I see there are quite a few guys on CL and Marketplace who sell these and seem familiar with inspecting and general overhaul. Since my woodie is far from being an original anything, why would I Not want to go this route? Right now, all seems fine, but I can now go 70 on the interstate and seems like a good move for piece of mind as I venture further from home in my 'semi-retirement' phase. Thanks, Gary
 

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Sounds like a good plan to me. Safer for you and yours and that truck you built is the only one like it on the planet. Axle failure at 70 MPH would be bad.
 
Gary, I hear tell, (no experience myself) that a 9" is overkill for a flathead, an 8" being more appropriate. Perhaps a comparison of options here would benefit your goal? I believe they both have the common ratios of 3.27, 3.55, and 3.73, the 9" being used for F250/F350, the 8" for F150. more info than that is above my paygrade.
 
I think it comes down to what do you have available and at what price? A 9" rear is definitely overkill from a strength perspective, but there are more parts available for 9" Ford rear ends than probably any other made.

However, a good 8" Ford rear is lighter, has all the ratios you could want and there were definitely some that were 5 x 5.5 bolt pattern. Either one will work - just find a good one at a fair price. ;). I think a gear ratio of 3.73 or 4.11 would work out fine with your overdrive setup. I would probably choose a 3.73 if I had a choice.
 
I'm using A 1999 8.8 from a merc mountaineer in my 1948 merc coupe. It has 3.73 gears, posi. and is 1/2" narrower than the original unit. I think a pre-1999 unit w/o disc brakes would work fine with your set up. they're pretty stout rears. just my useless opinion. lol, tom
 
ford38v8 said:
Gary, I hear tell, (no experience myself) that a 9" is overkill for a flathead, an 8" being more appropriate. Perhaps a comparison of options here would benefit your goal? I believe they both have the common ratios of 3.27, 3.55, and 3.73, the 9" being used for F250/F350, the 8" for F150. more info than that is above my paygrade.
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The F-250 and F 350 would be full floaters with 8 lugs. There were some F250s with semi-float but still 8 lug. These 3/4 amd 1 tons would typically have a dana 60, or in later years a sterling 10 1/4. The 4:11 is absolutely perfect for the island with so many hills and really 60 is more comfortable on the rare freeway trips. My rear tires are a bit over 30" tall so there's a little 'rubber overdrive' as well. Most of the 8 and 8.8 seem to be set up for the springs being under the axle, and mine are above. I have moved and welded spring pads before but the '57-'72 seem the best fit. I'm glad I have received a favorable response on this subject and thanks for the input. And I do kinda like a bit of 'overkill' sometimes. I will continue my research!
 
Hi Gary, Back in the day when I put a 9" out of a 64 thunder bird in my 42 jail bar. the width was good as in it looked right and the pinion yoke length worked as well. I did it for the 3.00 gears back then. The only issue was the lugbolt pattern but I just put on a set of custum wheels and all was well. Tim
 
I think something missing in this discussion is the weight on the axle. Engine torque and thrust are not the only considerations, the load carrying ability of the rear end structure and bearings should be considered as well as the braking torque on the axle housing (related to total weight of the vehicle). If Gary is not going to carry more weight than the 1/2 ton pickup at full capacity he should be just fine. If the rear end will be overloaded then think bigger. The 8" is a great little rear end (emphasis on LITTLE) and should be reserved (and preferred) for roadsters, coupes, and pre 1935 sedans.
 
I think it is a great idea - with parts, brake shoes, and the complexity of changing anything in a banjo rear, it really is a no-brainer, 9 or 8”. There are more readily available junk yard pumpkin gearsets for the 9 vs 8” rears so 9” overkill - yes - practicality the 9” is a clear winner in my book. Oh - if you are running a 5.5” bolt pattern go 9”.
Go for it!
 
A rear end from an earlier Bronco would be a good choice with 5 on 5 1/2 bolt pattern but they are more $$ than 1/2 ton units IIRC. Plus the springs are on top of the axle tubes, again IIRC. An 8 inch out of a Maverick would be a good choice based on it's 56.25 WMS to WMS but it's 5 on 4 1/2 and most are high 2's or low 3's ratios.
 
I think its a good idea. The rear that was popular with those darn kids was the 57 -59 ford car 9" rearend as it was the best match in width for the old Ford bodies.

61 1/4". 57-72 f100
57.1/4" 57 -59 car
I can't remember, is your open drive banjo wider than 48 cars?
 
Gary, This sounds like a good idea to me, from reading how much work is involved in working on brakes or axles, etc on a banjo-style rear. This may be a more HAMB related discussion, but there may be another option. Don't know if it would be much if any cheaper, but there is an outfit in California (Where else?) that can provide 9" axles, bearings, and such for your existing rear. It would probably involve a complete rebuild of the assembly anyway, tho. to get to where you would like to be.

Al Hook

Don't forget: "Murphy's law is one of the natural laws that you don't read about in the psysics books"
 
cas3 said:
I think its a good idea. The rear that was popular with those darn kids was the 57 -59 ford car 9" rearend as it was the best match in width for the old Ford bodies.

61 1/4". 57-72 f100
57.1/4" 57 -59 car
I can't remember, is your open drive banjo wider than 48 cars?
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Skip, probably so. The pickups got a 2 1/2" increase in width in '42. This was also true of the tonners. My '38 tonner express had 46 1/2" between rear fender wells in bed. Imagine what I went throgh as a cabinetmaker running that thing all those years. The jailbar tonner express has 49" clear! The tailgate closes too.
 
I've never seen an 8" with 5.5 bolt pattern. 8.8 sure...but not 8". A 9" from a pickup would be perfect. That's a good plan, GB, and you'll be glad you did it. :)
 
Gary
I would definitely stick with the 4.11 ratio. When driving the local rural roads in 3 speed standard drive, I’ve found it useful on the Tonner in combination with the engine compression to assist braking. Also useful when pulling a trailer or a parade float.
Les
 
cadillac512 said:
I've never seen an 8" with 5.5 bolt pattern. 8.8 sure...but not 8". A 9" from a pickup would be perfect. That's a good plan, GB, and you'll be glad you did it. :)
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I had one out in SoCal about 40 years ago (was going to use the axles in a banjo build) . . . I believe I still have the 28 spline axles in my Mom's garage. ;)
 
expavr said:
Gary
I would definitely stick with the 4.11 ratio. When driving the local rural roads in 3 speed standard drive, I’ve found it useful on the Tonner in combination with the engine compression to assist braking. Also useful when pulling a trailer or a parade float.
Les
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Last time I was in Hansville I didn't notice any superhighways! As far as the 4:11 goes, I have learned through 48 years on this giant rock that it's as tall as I want here. Keep in mind I'm partial to tall narrow tires, and HP just north of 100 at best. It's that Borg Warner OD that keeps me truckin' on Interste 5 :)
 
A 9 or 8” is alot easier to work on, parts are still readily available, and it’s a much stronger than a banjo, 8 or 9”, for a 1/2 ton truck. For me, I think 75 mph at 2500 rpm - there are calculators out there to figure this out w/5th gear ratio, tire diameter, gearset - a flathead’ needs hesat and its sweetspot is 22-2800 rpm. My avatar w/stock flathead can run 85 mph at 2800 rpm and never missed a beat and never overheated. Stick in the 8 or 9” - you won’t regret it!
 
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