M1070 HET Speed Improvement

[Mustangsud]

Has anyone with a HET undertaken modifications to get the speed up? Replacing four pumpkins can't be fun, but just curious about any mods.

My 55 mph trucks I want to run 65, but I'd be happy getting the HET just up to 55.

 

[simp5782]

Has anyone with a HET undertaken modifications to get the speed up? Replacing four pumpkins can't be fun, but just curious about any mods.

My 55 mph trucks I want to run 65, but I'd be happy getting the HET just up to 55.

Swap to a 7 speed Allison 4560P or a 4700sp with a 6th .74 would give you 16 more mph and a 7th .64 OD would add an additional 27mph.

Or a CAT 7155 would give you a 9mph improvement with the .83 OD


Cat would be the easiest and cheapest swap

Or a Spicer 18 speed. They can be had for around 3500 rebuilt

Or Any 13 speed for that matter.

There were a few eaton 18 auto shifts that came behind the DDEC II 8v92 so that would mate with the computer

 

[Mustangsud]

Swap to a 7 speed Allison 4560P or a 4700sp with a 6th .74 would give you 16 more mph and a 7th .64 OD would add an additional 27mph.

Or a CAT 7155 would give you a 9mph improvement with the .83 OD


Cat would be the easiest and cheapest swap

Or a Spicer 18 speed. They can be had for around 3500 rebuilt

Or Any 13 speed for that matter.

There were a few eaton 18 auto shifts that came behind the DDEC II 8v92 so that would mate with the computer

These are great ideas. Have you done or known someone who's done one of these conversions? I guess the mating of a new trans. isn't an issue since the 92 engine is very common. The Cat 7155 probably would be cheapest, but I have a 916 and all that air clanging and banging while shifting drives me nuts. Every time we take it somewhere people think that parts are about to start falling out underneath it as we go down the road.

I'll look into the Allisons. I've not ever done a trans. swap like this, so I'm not real sure what all it entails.

 

[simp5782]

It's on the drawing board to do. But with a repower as well.

The Allison from a garbage truck is what you want. They used 92 series

Cats aren't loud if you put a regulator on them and turn the air pressure down to about 85/90

HET uses an 1810 jackshaft. You will need a trans with an 1810 or 9c output yoke.

 

[simp5782]

These are great ideas. Have you done or known someone who's done one of these conversions? I guess the mating of a new trans. isn't an issue since the 92 engine is very common. The Cat 7155 probably would be cheapest, but I have a 916 and all that air clanging and banging while shifting drives me nuts. Every time we take it somewhere people think that parts are about to start falling out underneath it as we go down the road.

I'll look into the Allisons. I've not ever done a trans. swap like this, so I'm not real sure what all it entails.

Why does the cat bang and clang?

If you swap the vents for the metal bell type the air burst are much quieter.

You should only have to shift 3x for normal driving in that 916 from takeoff to max speed.

Start in 9th. 11th 13th 15th 16th

 

[Mustangsud]

Right now I’m first looking at replacing axle gears to improve speed, possibly even planetaries.
Initial estimate for putting in a 4700 rds transmission is about $50k. That’s a pretty steep hit for a little speed.

 

[simp5782]

Right now I’m first looking at replacing axle gears to improve speed, possibly even planetaries.
Initial estimate for putting in a 4700 rds transmission is about $50k. That’s a pretty steep hit for a little speed.

You can find a takeout from behind a 60 series detroit with harness and all that.

The 916s with the 7spd use a stand alone tcm and a a cable drawn tps for the 4700sp.

You could always but a parts truck mtvr and use that transmission and you have spare parts for yours.

A guy on here in Suriname did the PLS planets on his HET

Your could also just add auxiliary transmission behind the transfer case and leave it in OD. Moving the front axle engagement to it's own switch. So all rears could pull with the front freewheel while it's in OD. But you would need to shift it back to direct to use the front axle

 

[eaw46]

Absolutely amazing how much knowledge and experience is on this site. Where else could you find this kind of advice and help for free?

 

[Mustangsud]

You can find a takeout from behind a 60 series detroit with harness and all that.

The 916s with the 7spd use a stand alone tcm and a a cable drawn tps for the 4700sp.

You could always but a parts truck mtvr and use that transmission and you have spare parts for yours.

A guy on here in Suriname did the PLS planets on his HET

Your could also just add auxiliary transmission behind the transfer case and leave it in OD. Moving the front axle engagement to it's own switch. So all rears could pull with the front freewheel while it's in OD. But you would need to shift it back to direct to use the front axle

Thanks for the great ideas! I will add them to my list of possible solutions. I’m hoping to not have to go far down the list for a solution. The guys I have looking at it just did a job for FEMA changing out pumpkins on new trucks somebody ordered that would only run 45, so I’m hoping they find some gears!

 

[simp5782]

Absolutely amazing how much knowledge and experience is on this site. Where else could you find this kind of advice and help for free?

Pfft. Stupid questions cost folks $5

 

[Gunzy]

Has anyone looked at doing away with the planetaries in all the hubs and going to a direct drive? I would think that would increase speed albeit at the cost of low end torque.

 

[Mohawk piper]

Has anyone with a HET undertaken modifications to get the speed up? Replacing four pumpkins can't be fun, but just curious about any mods.

My 55 mph trucks I want to run 65, but I'd be happy getting the HET just up to 55.

Did you ever get the HET to increase speed? If so, how?

 

[crazyalaskan]

You can find a takeout from behind a 60 series detroit with harness and all that.

The 916s with the 7spd use a stand alone tcm and a a cable drawn tps for the 4700sp.

You could always but a parts truck mtvr and use that transmission and you have spare parts for yours.

A guy on here in Suriname did the PLS planets on his HET

Your could also just add auxiliary transmission behind the transfer case and leave it in OD. Moving the front axle engagement to it's own switch. So all rears could pull with the front freewheel while it's in OD. But you would need to shift it back to direct to use the front axle

Can I swap the transmission out on the M1070 HET that has the 8V92 and use a Allison HT-755 CR? I have a fresh rebuilt transmission sitting in my yard and I am eyeballing a HET in JBLM but I'm shy of the 45MPH speed. If I can get 55MPH I can manage.

 

[simp5782]

Can I swap the transmission out on the M1070 HET that has the 8V92 and use a Allison HT-755 CR? I have a fresh rebuilt transmission sitting in my yard and I am eyeballing a HET in JBLM but I'm shy of the 45MPH speed. If I can get 55MPH I can manage.

Yes. I have a source for a 7spd Allison 4700 that can handle 600hp. Has harness and all the applicable parts.

 

[crazyalaskan]

Yes. I have a source for a 7spd Allison 4700 that can handle 600hp. Has harness and all the applicable parts.

I have a Allison HT755CR transmission on hand. Was wondering of that could work?

 

[simp5782]

I have a Allison HT755CR transmission on hand. Was wondering of that could work?

It has the same final drive as the HET CLT754 so it won't gain any speed

 

[DeMilitarized]

Swap to a 7 speed Allison 4560P or a 4700sp with a 6th .74 would give you 16 more mph and a 7th .64 OD would add an additional 27mph.

Or a CAT 7155 would give you a 9mph improvement with the .83 OD


Cat would be the easiest and cheapest swap

Or a Spicer 18 speed. They can be had for around 3500 rebuilt

Or Any 13 speed for that matter.

There were a few eaton 18 auto shifts that came behind the DDEC II 8v92 so that would mate with the computer

@Elijah95