Toploader main shaft interchange

F

Fabulous50s

Junior Member
Hello all,

First time posting here of TFB. I have a question about a toploader the main shaft in an overdrive transmission and if it's the same as a straight 4 speed toploader.

I have a side mount overdrive (iron case) disassembled with the hope of a simple rebuild to install in my '59 Galaxie with a 352 FE.

I originally has a close ratio 3 speed toploader in it out of a '69 Galaxie so I have the later bell housing etc already.

My trouble is that my existing trans has a 27" main shaft and the O/D trans is a 24" main shaft.

If they are the same, I'm looking for a 27" 4 speed main shaft with 28 spline output. But I dont know if that is possible..... I'm not keen on cutting and welding these together.........

Pic attached is the 3 speed and O/D shaft for comparison.

Thanks!
 

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The T86 with Borg Warner OD is the only top loader I know of that has overdrive. The Ford Top Loader 3-speed & 4-speed made from 1964 up is a different set up than the light duty T86. The T86 was used in light duty applications beginning in the mid 50s but was basically replaced by the early narrow pattern T10 4-speed in early 60s applications.

The T85C or T85N with R11 overdrive is the heavy duty transmission with Borg Warner OD. They came out for Lincoln 337 use in 1949 and eventually worked their way into the performance Y block and FE block applications in the mid to late 50s. The nodular case T85N was used in heavy duty OD applications up into the very early 70s and can take about anything a 390 FE can throw at it.
 
I've called and emailed David Kee, and Dan Williams. Neither of them answers the phone or replies to any emails. A little frustrating.

I was looking at the Borg Warner with R11 O/D but they are going for crazy money over $1000 for all the ones I could find.

The Toploader I have is a T170F, which is really a 4 speed toploader modified to be a 3 speed with O/D.
 

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56sedandelivery said:
They can do that? The overdrive has a different case with provision for the overdrive gear.
Click to expand...

Yes, the case has a slight bulge for the O/D counter gear.

But I'm saying it's essentially a 4 speed that was converted to a 3+O/D. The counter shaft and syncros are all the same part as a 4 speed.
 
Can you just use the OD as is and get longer driveshaft? Galaxie's came with the long output shaft on 4 speeds, not sure on 3 speeds. Last year for manual in Galaxie was 1971. I know not helpful. Your OD was only used behind small blocks and 6's originally I believe, the input shaft may be longer than your 3 speed also. Going to need a transmission guru. Let us know if you get something figured out, I drove a 302 pickup with one of those OD,s It shifted fine but the 302 and gap in gears along with 55 speed limit made it unacceptable in a pickup.
 
Everything will bolt up and work other than the short output and the speedo cable on the wrong side. Both of these can be corrected by either getting a longer output shaft and being able to use my existing driveshaft and existing long tailpiece (from my 3 speed toploader I had in it). Or i can have a longer driveshaft made and get a longer speedo cable.

I was just thinking a longer main (output) shaft would be cheaper/easier....
 
I graphed 3 different transmissions to get a visual of the gap between gears.

I think the ratios for the "car unit" are quite acceptable.
 

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Thank you for the VanPelt link. Replied to my email and answered the phone! We are working on seeing if what I need was ever even made.

I should just give up and make it a 5 speed floor shift.....
 
The T170 RTS TOD transmission was purpose built as a 4-speed OD transmission mostly for F150, Bronco, and some F250 with 302 applications in both 2WD and 4WD. There are different main shafts for 2WD & 4WD applications. The overdrive gearing has three different ratios depending on the application.

The T170 SMOD, SROD, and TOD are all similar in design but they are different in ways that doesn't allow for much interchangability. They aren't as heavy duty as the earlier Ford top loader 4-speed.
 
Last edited:
Well discovered that there really is no such thing as main shaft interchange. Different bearing diameters and thicknesses. The truck versions have larger bearings, but are thinner.

So the plan is to use my Granada transmission and a van tail housing to put the speedo drive on the driver's side. I'll need to extend the driveshaft 3".

I scored another O/D unit from a wrecked van. Had 3 mount ears broken off and a broken bell housing bolted to it. Was able to use 1st gear, the tail housing, and a few odds and ends. Otherwise the whole thing was junk. Galled main shaft etc.
 
Now I have 3 toploaders completely disassembled and will use the best parts from the 3.

Rebuild kit should be here this week.
 

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No, it depends on if the speedo gear is over or under the drive head on the main shaft. Mine was originally over the shaft 6 tooth. Now it will be under, so a reverse thread but still 6 tooth.
 
Make sure the pitch of the speedo gear on the tail-shaft and the driven gear on the speedo cable match each other. Not sure if they can be right or left handed but check first.
 
Color codes for the gears are available. You just need to make sure the cable is spinning the correct direction and is 1,000? revelations/mile.
 
Fabulous50s said:
Well discovered that there really is no such thing as main shaft interchange. Different bearing diameters and thicknesses. The truck versions have larger bearings, but are thinner.

So the plan is to use my Granada transmission and a van tail housing to put the speedo drive on the driver's side. I'll need to extend the driveshaft 3".

I scored another O/D unit from a wrecked van. Had 3 mount ears broken off and a broken bell housing bolted to it. Was able to use 1st gear, the tail housing, and a few odds and ends. Otherwise the whole thing was junk. Galled main shaft etc.
Click to expand...

Hi,
Right, the parts are not really interchangeable with 4 speed top loader. You have a 3+1 toploader, same DNA, but different parts. As far as I know, 3+1 all used the bigger 40/90mm 308 sized bearing, not the 45/85mm 209 4 speed toploader bearing. So input and output shafts won't swap.

Your iron case is a side shift RUG, but not a 4 speed RUG. It is a 3+1 RUG and has the bulge in the RH side of case. The later RTS trans was similar, but with aluminum case and top shifter for trucks

There were actually several 1, 2, and OD gear ratio combos made in the RUG 3+1, compared to only narrow and wide in the 4 speeds.
What is the two character code after "RUG" on the steel tag on RH side?

Check this page for more info:
http://www.fordgarage.com/pages/TremecT170FT.htm
 
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