HEH-BX VS. HEH-BT Close ratio Toploader - What are the differences?

[6s1640]

Hi all,

This is only slightly related to the 66 GT350, only by day-2 modifications, tranny swaps back in the day, automatic to four speed.  The Toploader was likely the tranny of choice.

Can any one tell the difference between the HEH-BX and the HEH-BT Toploaders?  Both are close ratio four speeds, built on the same case C5AR-7006-D.  The HEH-BX according to Mustangtek was from October 1, 1964 for both 1965 and 1966 Mustangs, both HiPo and LoPo 289.  The HEH-BT was from February 1, 1965, four months later only ID'd for 1965 Mustangs.  I assume for LoPo 289's only.

Did the HEH-BX have better bearings or some other difference to make it more heavy duty?  Was the HEH-BT a little cheaper to build for the LoPo 289 Mustangs, but then dropped for 1966 model year, maybe because the savings really was not there?

Thanks

Cory

[S7MS427]

Cory,

Here goes to the best of my knowledge. The HEH-BT box is a wide ratio transmission and the HEH-BX box is a close ratio transmission.  I'll have to dig deeper into the MPC to confirm.  Bearings should be the same for all toploaders.  It is possible to put in a "max-capacity" bearing that has an extra ball bearing rated for a higher radial load but that is at the expense of thrust loading.  So those two transmissions should be virtually identical except for the cluster gear, input shaft, and second and third gears.  I've rebuilt a bunch of these gearboxes and do have some knowledge of what I'm talking about.  IMO, the toploader is a much better transmission than the T-10 which I wouldn't use if you paid me.  Hope this helps and if anyone has better information, I'm always ready to learn.

[Bob Gaines]

Cory,

Here goes to the best of my knowledge. The HEH-BT box is a wide ratio transmission and the HEH-BX box is a close ratio transmission.  I'll have to dig deeper into the MPC to confirm.  Bearings should be the same for all toploaders.  It is possible to put in a "max-capacity" bearing that has an extra ball bearing rated for a higher radial load but that is at the expense of thrust loading.  So those two transmissions should be virtually identical except for the cluster gear, input shaft, and second and third gears.  I've rebuilt a bunch of these gearboxes and do have some knowledge of what I'm talking about.  IMO, the toploader is a much better transmission than the T-10 which I wouldn't use if you paid me.  Hope this helps and if anyone has better information, I'm always ready to learn.

It seems Ford is in agreement given it was phased out in later 66 to the toploader.

[6s1640]

Cory,

Here goes to the best of my knowledge. The HEH-BT box is a wide ratio transmission and the HEH-BX box is a close ratio transmission.  I'll have to dig deeper into the MPC to confirm.  Bearings should be the same for all toploaders.  It is possible to put in a "max-capacity" bearing that has an extra ball bearing rated for a higher radial load but that is at the expense of thrust loading.  So those two transmissions should be virtually identical except for the cluster gear, input shaft, and second and third gears.  I've rebuilt a bunch of these gearboxes and do have some knowledge of what I'm talking about.  IMO, the toploader is a much better transmission than the T-10 which I wouldn't use if you paid me.  Hope this helps and if anyone has better information, I'm always ready to learn.

Hi S7MS427,

I am confused.  Both Mustangtek and David Keys of Toploader fame both say the HEH-BT and BX are close ratio.  You saying the HEH-BT is a wide ratio is in conflict.  What can you show that tells me these two sites are wrong?  Both being close ratio is why I asked the question. Thank you for your input.

Cory

[98SVT - was 06GT]

This is a handy fitment chart on Toploaders  http://www.davidkeetoploaders.com/idchart1.htm

HEH-BX   1966   Mustang   289, 289K   close   From 10/1/64

HEH-BT   1965   Mustang   289   close   From 2/1/65

You'd need to go the parts book and compare all the components to find the difference. Could it be as easy as input/output spline differences? Or it could be as simple as a casting change to the thickness of the casting or addition of some more meat around the shifter mounting boss (you'd have to have access to the original engineering plans for those). But then again X was used for experimental and HiPerf parts and maybe the change to T was just to denote it as a regular production part.

Maybe this is the answer???

The case on the right is a 64 narrow bolt pattern 4 hole case (X??).The case on the left is a 65-73 wide bolt pattern 8 hole case (T??). The inner bolt pattern on the 8 hole case is the same pattern as the early narrow case.

Randy.......HELP

[S7MS427]

Cory,

This why I worded my response the way I did: "to the best of my knowledge" and "if anyone has better information, I'm always ready to learn".

I know I researched this subject years ago and may have dug this tidbit out of an old MPC from years back (pre 1965-1972) which I no longer have access to.  Or it could be buried in my archives somewhere.  Or I might have just plain gotten it wrong.  I do like to have written verification for the things I post.  So I'll just let someone else chime in who has better information.  Unless of course I can locate my source.

[6s1640]

This is a handy fitment chart on Toploaders  http://www.davidkeetoploaders.com/idchart1.htm

HEH-BX   1966   Mustang   289, 289K   close   From 10/1/64

HEH-BT   1965   Mustang   289   close   From 2/1/65

You'd need to go the parts book and compare all the components to find the difference. Could it be as easy as input/output spline differences? Or it could be as simple as a casting change to the thickness of the casting or addition of some more meat around the shifter mounting boss (you'd have to have access to the original engineering plans for those). But then again X was used for experimental and HiPerf parts and maybe the change to T was just to denote it as a regular production part.

Maybe this is the answer???

The case on the right is a 64 narrow bolt pattern 4 hole case (X??).The case on the left is a 65-73 wide bolt pattern 8 hole case (T??). The inner bolt pattern on the 8 hole case is the same pattern as the early narrow case.

Randy.......HELP

Hi 98SVT,

The HEH-BT and BX have the same wide bolt pattern with 8 holes like your image of the tranny on the left.  This further confuses me why both existed.   I too was hoping Randy would chime in.

I think you're right on going thru the MPC, but I expect the copy I have, 1975 MPC won't give me any clues.  Because the two tranny's are very similar, I expect Ford only carried service parts in 1975 that would work on both, so finding a difference may not even exist in the 1975 MPC.  Maybe a very early MPC would show the differences.  I was hoping someone would know right of the bat on here.  The quest goes on.  I should call David Kee and ask him.  I will update after talking to him.

My look at the MPC shows for HEH-BT and BX to use parts list 70.6.  This parts list includes all the Ford 4 speeds.  Once in the list, I cannot see any application commentary to separate the two.  Any differences I am finding appears to be with the wide and close ration tranny's, like the cluster gear.  Close ratio C4AZ-7113-B (HEH-BT and BX) and wide ratio C4DZ-7113-B (HEH-BR and BW)  I will keep looking.

Thanks all

Cory

[S7MS427]

Right guys, that's why I think I pulled my info from a pre 65-72 MPC.  Agreed we need Randy on this.  The splines on the small block input shaft are all the same BTW.  Outputs could be either 25 or the much more common 28 spline, IIRC.

[98SVT - was 06GT]

Outputs could be either 25 or the much more common 28 spline

Therein may be the difference

[S7MS427]

No that's not it.  The 25-spline boxes were tagged HEH-L and HEH-N (HEH-L before 12/1/1964).  Those were the only 25-spline gearboxes I could find.  Surprisingly, the HEH-N is listed for use with a Hi-Po.

[6s1640]

Hi guys,

I sent a note to Perogie.  They rebuild a lot of these Toploaders.  From Steve's memory too, the only difference is in the detent system, springs (7234) and pins (7C316 and 7235).  Ford was trying to improve the shifting with the HEH-BT but latter dropped.  It must not have worked as well as they thought.   I could not find any differences in the MPC, suggesting maybe Ford only serviced the HEH-BX detents.  This is the answer I got back:

"The HEH-BT and BX interchange perfectly, both close ratio small spline, 28 spline, wide case units, but the earlier BT had the first revision detent system and Ford theoretically "Improved" the system changing the detents slightly  They also changed the case as most BT's I have seen are on the mid-case lettered C5AR case (C5 casting number is in the center of the side of the case) and the BX's are usually on the more conventional High letter location for the lettering.  Ford always changed the number in case of a recall or issue, but overall they were identical - and when I say the detent system changed, it was merely just a change in the spring and detent pin sizes,    This is going off my head but if I think of any other changes on em when I see the bigger kahuna (who even with my 30 years around here, still knows alot more than me) if he knows any other differences."

Thanks all

Cory

[S7MS427]

Cory,

Surprise, surprise. I worked with Perogie for a number of years.  In fact I taught them how to rebuild toploaders.  Yes George ("the bigger kahuna") would probably know the differences.  They make their knowing the detail differences.  The question for me is are both of these boxes CR and where the heck did I pick up the notion that the -BT is a WR?

As for detent pins and shift rails, if you change everything out as a set, things work out.  But mix them together thinking you can replace one part with another from a different style set and you may find that the box won't shift at all.  Learned that the hard way.  FWIW, I feel that the early style detent set with the beveled pins work better than the later style with the pointed pins.  I think Ford was just trying to save manufacturing money by machining a less costly pointed detent spring.  Not as many machining steps to put a point on a cylinder verses a two sided bevel on each end.

[sg66]

Comments to a post on the Hipo Mustang site a few years ago from Fred Ballard:

an HEH-BT is NOT a close ratio and is NOT for a Hipo. The identifier information that is out there on the internet toploader sites is in error. They also have an error on dates used for the HEH-T transmission and this comes directly from the Ford MPC which is in error on that transmission. We had HEH-T transmission with stamped VIN's on the original Hipo site with Kar production dates as late as May 1965. The toploader sites show that transmission from 8-20-1964 to 10-1-1964 which matches the Ford MPC but that information is in error. If you are in doubt, ask the seller how many teeth are on the second gear. 28 is a close ratio and 31 is a wide ratio

https://hipo-mustang.com/thread/5596-heh-bt/

[6s1640]

Comments to a post on the Hipo Mustang site a few years ago from Fred Ballard:

an HEH-BT is NOT a close ratio and is NOT for a Hipo. The identifier information that is out there on the internet toploader sites is in error. They also have an error on dates used for the HEH-T transmission and this comes directly from the Ford MPC which is in error on that transmission. We had HEH-T transmission with stamped VIN's on the original Hipo site with Kar production dates as late as May 1965. The toploader sites show that transmission from 8-20-1964 to 10-1-1964 which matches the Ford MPC but that information is in error. If you are in doubt, ask the seller how many teeth are on the second gear. 28 is a close ratio and 31 is a wide ratio

https://hipo-mustang.com/thread/5596-heh-bt/

Hi SG66,

Interesting.  I do know Fred and I expect there can be errors in the MPC.  But Fred is half right.  The HEH-BT was never identified as HiPo in the MPC.  So Fred is correct, the HEH-BT was not used with the 289 Special.  However, I disagree with with the HEH-BT not being a close ratio.  Everything I read says it is a close ratio.  I have a HEH-BT and a HEH-BX.  I will count the input/output rotations on both to confirm close ratio and let you know.  I will also count some teeth.

Thanks for the input.

Cory

[6s1640]

Cory,

Surprise, surprise. I worked with Perogie for a number of years.  In fact I taught them how to rebuild toploaders.  Yes George ("the bigger kahuna") would probably know the differences.  They make their knowing the detail differences.  The question for me is are both of these boxes CR and where the heck did I pick up the notion that the -BT is a WR?

As for detent pins and shift rails, if you change everything out as a set, things work out.  But mix them together thinking you can replace one part with another from a different style set and you may find that the box won't shift at all.  Learned that the hard way.  FWIW, I feel that the early style detent set with the beveled pins work better than the later style with the pointed pins.  I think Ford was just trying to save manufacturing money by machining a less costly pointed detent spring.  Not as many machining steps to put a point on a cylinder verses a two sided bevel on each end.

Hi Roy,

See, we are smarter together.  Yes, I agree, mixing the springs, pins and shift rails would not be a good thing.  That we can agree on.

I cannot address your memory on the HEH-BT ratio.  That is why we need each other so we can help each other remember better.

Take care

Cory