1970 F100 drivetrain questions?

[det45]

I recently purchased a 1970 F100 Ranger with the 360 2bbl, C6 transmission, and a nine inch open 28 spline differential. My question is why did Ford use the open 28 spline 9" differential on the majority of the late sixties early to mid seventies F100 pickups when a 31 spline Traction-Loc nine inch differential was available? One would think all full size pickups from that era would have the stronger set up? Lastly how strong is the open 28 spline 9" differential, should it be any concern with moderate engine upgrades? Thanks........det45.

[Ranchero50]

Cost and use / duty. You need to maintain the T-lok, clutches every couple years and it either works or doesn't. I suspect Ford didn't want the warranty hassle. A truck's tires and chassis is soft enough that a 28 spline is fine for 99.9% of folks. I'd trust them over a rusted pencil thin drive shaft any day for a higher HP sticky tire launch.

[ultraranger]

The only 31-spline axles/differential used in the Bumpside F100s was with the optional Ford 9-3/8" rear end. This was only in the '68-'72 models and not '67. The 9-3/8" rear end is similar to the Ford 9-inch rear end but not the same.

There were two versions of the 9-3/8" 31-spline axles used in the '68-'72 F100s. If the differential was open (single track), the axles were rated for 3300# and used 3-9/64" O.D. by 1-17/32"I.D. ball bearings. If the 9-3/8" 31-spline axle came in the rear end with a Traction-Lok differential, the axles were rated for 3600# and had roller axle bearings measuring 3-9/64" O.D. by 1-5/8" I.D.

Either version of the 9-3/8" 31-spline axles (3300# or 3600#) will fit into the 9-inch rear end housing of a '68-'72 F100. I have a pair of 3300# 9-3/8" 31-spline axles in the stock 9-inch housing under my '69 F100, along with a 31-spline Traction-Lok differential in a Ford 9-inch N-case 3rd member that came out of a '75 F150 4x4.

[det45]

I'm thinking I'm just going to add a 28 spline trac-loc 9" third member and call it even. That way I can use the original axles & brakes not to mention that my stock 360 2bbl automatic is no threat to the differential. I've seen 28 spline trac-loc third members for sale on eBay for around $900.00 bucks.

[sargentrs]

If all you're looking for is limited slip, you can use your existing carrier and install a PowerTrax No Slip. About half what you were going to spend.

https://m.summitracing.com/parts/pwt-92-0690-2800

So easy to install even I could do it. Installation is in my build thread starting on page 11. I haven't actually driven with it yet but I'm expecting good things. The Mustang crowd spoke highly of it.

[Madman]

If all you're looking for is limited slip, you can use your existing carrier and install a PowerTrax No Slip. About half what you were going to spend.

https://m.summitracing.com/parts/pwt-92-0690-2800

So easy to install even I could do it. Installation is in my build thread starting on page 11. I haven't actually driven with it yet but I'm expecting good things. The Mustang crowd spoke highly of it.

I installed the PowerTrax in the front and rear of my 48 CJ2A, only issue I see is at times it makes a pop/clunk occasionally which at first is unnerving but you get use to it. I think it is just unloading, and is mentioned in the installation manual that it is an expected noise and not a worry.....been in well over ten years, no issues, and helps me get the jeep into places while elk hunting that most people label me as "Just Nuts" to do....

[ultraranger]

I retained my stock '69 9-inch rear end housing and rear drum brakes. I swapped out the common C7AW-E single track 9-inch 28-spline 3rd member for a 9-inch Daytona Ford N-case D0OW-B 3rd member with a 31-spline, 4-pinion Traction-Lok differential with 3.50 gears from a '75 Dentside F150.

I changed out the 28-spline axles in the 9-inch housing and replaced them with 31-spline axles from a '71 F100 9-3/8" rear end.

The N-case Traction-Lok 9-inch 3rd member cost me $75.00. The pair of '71 F100 9-3/8" 31-spline axles (shipped) cost me $245.00. Total of $320 for all of this. This was easier and cheaper than me swapping out the open differential in my truck for a Traction-Lok. I didn't have to set the gears up in the 3rd member and I gained the ultimate in strength for 9-inch 3rd members (Daytona N-case) and I got 31-spline axles/differential.

[sargentrs]

Great deal, ultraranger!

[59yblockf100]

9 inch is a very strong and hard to break,9 3/8 is even better if you can find one,

[ultraranger]

9 inch is a very strong and hard to break, 9 3/8 is even better if you can find one,

The '68-'72 F100 9-3/8" rear end is heavy-duty. The main problem is there's no factory or aftermarket support for them --particularly for the ring and pinion gears. No one makes new gears for these rear ends so, if the gears get worn, chipped or broken, that's the end of it unless you can find an NOS gear set or a decent wrecking yard donor to get them from.

I believe their only ratios (9-3/8" truck rear ends) was 3.25, 3.50 and 4.09.

[tc399]

Howdy. This is my first post and I apologize in advance for the length instead of just saying less...

Id don't have a Fors and I haven't since they stopped making 4x4 Trucks with front and rear limited slip available. I used to have a bunch of Pintos, too and they were absolutely bulletproof except for that one small issue...but I loved mine and you could put in Stellite valves and a turbo and blow of RX-7s all day long.

Now I have an 03 Jeep TJ. I bought it with a blown sewing machine engine and I put in a 383 Chevy stroker motor with a 4L60 trans. which will make the rear end a pretzel if I ever step in it. Soooo, after 20 months of looking, I found a Ford 9" posi the right width. The guy gave it to me for hauling it away. I happen to know that 500 hp won't bother that rear end a bit - if I can rebuild it. I can't find the parts I need. There are no old-school parts guys left and the new guys are stupid. I tried for some American made axle bearings. I took the part number and measurements to several places and they looked at me like my hair was on fire. I tried the Internet but you have to know the make and model it came out of and I don't know - but I suspect this is an optional rear end for something because it's narrow and beefy and the part numbers don't cross to anything that I can find. I'm pretty sure it's a 9", but the pictures I see show the cast double-crosshatch pattern on an 8.8". I don't know the spline count - I didn't think to ask.

I ordered some Timken bearings for a '70 Ford F100 based on the measurements. Then I came here. When I saw that the ringleader of this forum has a '70 Ford F series, and that everyone here actually knows what they are talking about, I thought I was in heaven and joined up.

I'm looking for a parts list and parts diagram for my axle. I need most of the ancillary parts - some are missing, some just don't look too good. I have the axle sitting in a garage down the road where the guy is doing the work for me and I can get anything you want off of it. In the meantime, the axle tag reads EXACTLY like this, no more, no less:

WDT-AS4 8LB
2L80 9 . 3 292A

I think I can read it but it's not really helpful to me without your (et al) expertise.

The axle bearing part number is the same one everyone else is trying to find: FPP F208-AKK, but they turn out to be what I think were standard Ford bearings. 1.53" ID, 3.15" OD. If you can find a parts counter guy who can cross that number, I'll buy him a beer. McGuire bearings couldn't cross it either. No one can cross "FPP" either. It might mean Ford Proprietary Part.

Have a great day...thanks for listening!

Best Regards
T