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TR4/4A TR4 OD Main shaft?

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DickR

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TR4 OD
The OD and main shaft are new (used) to me. When I try to assemble the OD to the transmission, even with the pump cam and springs removed, there is a gap of about 1/8" between the tranny and the adaptor plate. It looks as tho the mainshaft has been modified. Does anyone know what the dimentions of the main shaft are? From the output bearing retaining ring grouve to the end of the shaft and to the end of the splines? The OD showed evidence of a very thick gasket when I recieved it. OD SN 22/1274/00498.3
Thanks for any and all help. Dick
 
Hello Dick,

it is not easy to mate the O\D to the gearbox, particularly if you don't have the special tool to align the internal Overdrive splines. When you look down inside the Overdrive you will see the splines that are driven by the mainshaft. What is not necessarily obvious is that there are two sets of splines, one behind the other and unless they are perfectly in line, the Overdrive will not go on. If you tighten the jacking bolts and it goes tight, do not overtighten or you will crack the gearbox backplate.
As I don't have the correct alignment tool I use a long screwdriver to align both splines, and sometimes it takes two or three goes. I assist it with a heavy soft hammer, but carefully.

Alec
 
Dick,
I just went through all this (see my "overdrive adventure continues" post). I had a hard time with the same thing and I took measurements of the shaft to figure out where the problem was. Here is what I have in my lab book.
Overdrive shaft total length: 6.5"
tail end (distal to the slines): 13/16" long and 0.626" dia.
back of cam sline to end of shaft 6-5/8"
back of main sline to end of shaft 8-13/16"
input end (not slinned): 1-7/16" long and 0.6865 dia.

I ended up developing a trick to work around the problem of joining the two parts. Since the gear box is heavy and has to be lowered onto the overdrive unit, I wanted to be darn sure they went together (I had your problem the first time). What I did was removed the main shaft from the gear box so all I had was that. I then clamped the overdrive unit vertically with the input up into a wood vise. Now I looked down into the overdrive and made sure the two sets of splines (that others have talked about) were in line. Also make sure there is no crud or other bits inside the bushing at the end where the shaft enters. I cleaned out the bushing. Then with the eccentric cam removed from the shaft I tried to inser the shaft into the overdrive. It took a long time and several tries but at one point it went in. Now you will know it is far enough by sliding the eccentric cam into place. If you are down far enough the cam will lign up with the pump bearing. Now for the "trick" I came up with. WITHOUT removeing the shaft wrap the output of the overdrive with masking tape very tight so that you lock the output flange to the case of the overdrive unit. Make sure you have it wrapped enough that it can't move. Now you can remove the shaft, build your gear box up and then go through the usual procedure of holding the pump back with wire and lower the gear box onto the overdrive unit. Remember to set the gear bos into fourth gear and turn the INPUT of the gear box to line up the splines with the locked (by tape) ones of the overdrive unit.

Doing it this way I found it went down just fine.

You mentioned the thick gasket. yes the gasket there is a thick one.

If you are still having problems let me know I will try and talk you through it. I just did this to mine yesterday so it is fresh in my mind (my web site will have a fill description and pictures soon as well).
 
I agree, if it was just the mis aligned splines it would be more like an inch or maybe a bit less, like 3/4".

Let us know how you make out.
 
Hi Alec and Ardo--
Thank you both-- I will get into the unit some time this week and let you know how it goes.
Dick R.
 
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