Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Ride of the Month Challenge!

1 - 8 of 8 Posts

·
Registered
Joined
·
2,596 Posts
Discussion Starter #1
I have two toploaders -- one in my 66 fastback and the other I am going to rebuild for my next project. The uninstalled unit is an HEH-P model, which was used during the first half of the 1965 model year.

The uninstalled gearbox has the 25-spline output shaft, as opposed to the one in my fastback, which has the 28-spline output shaft. I am told the 28-spline units are quite a bit more robust than the small shaft units.

My question is this: Can this gearbox reasonably be upgraded to 28-slpine specifications? I'd like to put it behind a 331 stroker I am building and do not want to see it break.

I sent an email asking this question of Mark at Toploader Heaven a couple of weeks ago but did not get a response. I appreciate that he is a very busy small business owner, and am not surprised that he cannot afford to drop what he's doing and answer every inane question that is sent him.

So, I hoping someone on the Forum can help before I start ordering parts.

Am I wasting my time with this gearbox?
 

·
Registered
Joined
·
371 Posts
I've been doing some looking my self and if you match all interior parts it should work fine , Input and output shafts and gears are also matched to shaft size . It may get expensive and may be cheaper to find one done and set up allready .
 

·
Registered
Joined
·
2,596 Posts
Discussion Starter #5
Thanks for the link to the Ford Tranny forum. I've put the question out there...Let's see what they say.

Actually, I'd posted on that forum before with questions about this upgrade and got only one inane response. I hope to do better this time.

We'll see.
 

·
Registered
Joined
·
10,344 Posts
IIRC, all you need to do is swap in a 28 spline output shaft. The rest of the internals are the same. You may also need to change or modify the tailhousing. I don't know if there is a difference in diameter of the 25 vs 28 spline yoke.
 

·
Premium Member
Joined
·
7,376 Posts
Is the case the 5 bolt narrow face case, or the wider 6 bolt case? Virtually all the 25 spline toploaders I have seen have been 5 bolt cases. To replace input/outputs, plus all the other work to be done, I would question the economics of the job. Is your block a 5 or 6 bolt case. If it is a 6 bolt block, then the 5 bolt toploader will not fit anyway.
 

·
Registered
Joined
·
2,596 Posts
Discussion Starter #8
Bob -- This is the case with bolt patterns for either 5 or 6 bolt setups. The engine I'm building is based on a 6-bolt, 67 289.

It is a rather strange gearbox, used only for 6 months, from the beginning of the 65 model year in August through January of 65. It also has the dual-purpose tail housing with bosses cast to mount either a Mustang or Falcon shifter. I bought it from another VMFer a few years ago and put it back in the corner of my garage. The 331 is in progress, so I thought I'd better look it over and get the parts I need to build it. That's when I found out that it is an HEH-P 25-spline box.
 
1 - 8 of 8 Posts
Top