Transmission / Overdrive: Operating B.W. T86E 3-speed O.D.

[rrausch]

OK... as I've been posting, I'm helping my buddy Bob restore his dad's '49 Studey truck, and I've rebuilt a T86E 3-speed O.D. trans for his truck. It's going behind a Stude 259 V8 that we're rebuilding this summer.

So you'll have to pardon my ignorance, but I've never messed with an O.D. trans before.

Bob wants a floor shift, and so I came up with a T-90 floor shifter and am in the process of mating it to the T-86 trans. Now in stock configuration on this O.D. trans, the 1st/Rev shift arm, when rotating into the Rev position also pushes a little plunger that... does something...maybe disabling the O.D?

My question is this: Now that I'm putting a floor shift on the trans, do I also have to rig up some sort of extra lever or cable for Bob to pull out to move the Rev shift arm when he wants to back up? Or can he just push in the O.D. cable and accomplish the same thing?
Thanks for any help on this.

[r1lark]

Well..........you could pull the OD cable everytime you need to backup, but IIMO that would get really old after a while.

Usually there is a tab welded to the rear shift fork to contact the OD lockout rail. I've got pictures somewhere of at least one, but would need to find them. Others have left the original side shift mechanism in place (I belive they have to be somewhat modified though) so as the top shift moves the gears, the original side shift mechanism moves also. Thus the OD lockout rail gets pushed back when shifted into reverse.

[rrausch]

Welding a tab to the rear shift fork is a good idea if it can work. A picture would be great if you could find one. Thanks.

The original 1st/Rev side-shift lever is intact on this trans.

[Ron Dame]

The overdrive engages at ..what....24-27 MPH? If you are backing up that fast, you deserve to blow up your overdrive.
Later on, that whole rail and switch was eliminated when they realized the rediculousiness of it all.

OK... as I've been posting, I'm helping my buddy Bob restore his dad's '49 Studey truck, and I've rebuilt a T86E 3-speed O.D. trans for his truck. It's going behind a Stude 259 V8 that we're rebuilding this summer.

So you'll have to pardon my ignorance, but I've never messed with an O.D. trans before.

Bob wants a floor shift, and so I came up with a T-90 floor shifter and am in the process of mating it to the T-86 trans. Now in stock configuration on this O.D. trans, the 1st/Rev shift arm, when rotating into the Rev position also pushes a little plunger that... does something...maybe disabling the O.D?

My question is this: Now that I'm putting a floor shift on the trans, do I also have to rig up some sort of extra lever or cable for Bob to pull out to move the Rev shift arm when he wants to back up? Or can he just push in the O.D. cable and accomplish the same thing?
Thanks for any help on this.

[rrausch]

Thank you Ron Dame--it's things like this that I need to learn. It makes sense, I'm just very inexperienced with O.D. units. Anybody else have any feedback on whether I need to consider that Rev. shift arm when I hook everything up?

[r1lark]

The overdrive engages at ..what....24-27 MPH? If you are backing up that fast, you deserve to blow up your overdrive.
Later on, that whole rail and switch was eliminated when they realized the rediculousiness of it all.

Ron, the OD lockout rail (actually called the OD shift rail) disengages the OD so you can back up. Without doing that, youi won't back up at all, much less get up any speed <G>. What you are thinking about is the lockout switch which was dropped in the mid-'50s IIRC.

[rrausch]

So I guess it's back to making the shift rail disengage the O.D.

[gordr]

Here you go: http://forum.studebakerdriversclub.c...school+shifter

[rrausch]

Thanks Gordr. That's the same top-loader shifter I have--a T90-148. It's good to hear from someone who has done this! Thanks.

[rrausch]

Gordr, what did you do to move the 1st/Rev shift fork?

The fork itself appears to be forged, and the shaft it slides on is hardened--I couldn't do anything but scratch the shaft with a file. The fork is positioned on the shaft with what looks like a 1/8th inch pin. I'm thinking about pulling the shaft out, annealing it and drilling it in order to relocate the shift fork. Comments?

Here's a picture

[Ron Dame]

Ron, the OD lockout rail (actually called the OD shift rail) disengages the OD so you can back up. Without doing that, youi won't back up at all, much less get up any speed <G>. What you are thinking about is the lockout switch which was dropped in the mid-'50s IIRC.

Guess I'm confused..a state I am very familiar with. If you have no electrical contact to move the solenoid, how could it go into overdrive in reverse? I guess I really did not understand the function of the rail and thought it was just an anachronism that really did nothing anymore.

[gordr]

Robert, I didn't have to move the low-reverse shift fork. There are several different cases used in T86 and T90 transmissions, and not all T90 top covers will readily fit T86 cases. There may be also some differences in total throw on the shift forks when you mix and match like this. In my case, the cover and forks were compatible, as-is. If your cover does not fit all 6 holes on the case, then you may have to experiment to find the right orientation of the cover, so that both forks move their associated gears to the desired limits. You should be able to determine this by carefully measuring the travel of each gear relative to a fixed point (say the front face of the transmission case), and then measuring the travel of each fork relative to the same datum. Those values should be the same; if not figure out what you have to do to bring them into agreement. Or find another top cover. There is a top cover shifter made for the later model T86 long-tail transmission, because I have a NOS taxi transmission that has one.

Ron, you do need to move the OD shift rail. The solenoid isn't the issue, it's the sprag clutch. With the OD shift rail in the forward position the sun gear is positioned such that, without the solenoid being energized, all torque flow is through the sprag clutch, which is the one-way device that allows free-wheeling. Engage reverse, and the mainshaft just spins, and you won't move. Probably, things will get broken, too.

Once you have a top cover that works right with the gears in the main transmission case, adding the finger to operate the OD shift rail is a pretty simple matter.

[rrausch]

Thanks Gord. This T90-148 top cover fits the bolt holes exactly. I'll do some measuring on the throw and the gear movement, and try to post the results later today.

[rrausch]

Mystery (I think) solved!

Take a look at this picture: See the orientation of the 1st/Rev slider gear? It's positioned so the shift collar is toward the rear of the trans. This is the picture I took of the trans as I was disassembling it in preparation for replacing the cluster and 1/st/Rev gear. This is the picture I referred to when I put this trans back together.



So I was measuring things trying to figure out how much I'd have to reposition the 1st/Rev shift fork, and it looked like it would work pretty good if only that shift collar were on the front of that gear... and I had an "ah ha" moment, and looked in the Shop Manual--sure enough it shows the gear with the collar facing the front. So I looked at a picture I took of another T86E--a non-OD trans, and it has the collar facing front too. LOOKS LIKE WHOEVER REBUILT THE TRANS PREVIOUSLY INSTALLED THE GEAR WRONG! No wonder it broke! Here's the picture of the second trans:



I can't say for absolute certainty, but right now it looks like all I have to do is flip that gear around and my top shifter will be shifting correctly. I will still have to fab up something to disengage the O.D. but at least ONE Problem might be easily fixed. I'll let everybody in about an hour--I should be able to flip it around in that time.

[rrausch]

OK, I pulled the trans apart and flipped the 1st/Rev gear around, and while I'm still going to have to make a small adjustment to that shift fork, it's much more doable that the way it was! Took me about 45 minutes--not too shoddy!