Know the Difference Between the HMMWV 6.2L and 6.5L Detuned Engines? Anyone seen this

[DukeNukem]

[h=1]Know the Difference Between the HMMWV 6.2L and 6.5L Detuned Engines[/h]
https://halfmastpsmag.wordpress.com...ween-the-hmmwv-6-2l-and-6-5l-detuned-engines/

 

[INFChief]

Let’s kick this thread back to life. So we know how to ID a 6.5 over a 6.2 but what are the differences in the engine itself? And, these might be a direct bolt-up but are all wiring harnesses & connectors & accessory brackets direct bolt ups or are mod kits needed?

 

[springer1981]

Let’s kick this thread back to life. So we know how to ID a 6.5 over a 6.2 but what are the differences in the engine itself? And, these might be a direct bolt-up but are all wiring harnesses & connectors & accessory brackets direct bolt ups or are mod kits needed?

Not an expert but from what I understand, with wiring, the difference in engine harnesses comes down to v-belt vs serpentine and 4spd vs 3spd. As with anything else, as time goes on and they change design, the parts and connectors change too. An early glow plug harness for example is $50 and many buy it thinking it fits their truck only to be disappointed when they try to install it. There is NO replacement for looking it up in the TM's and getting the right stuff. In general the trucks all use the same basic design and nearly everything can be retrofitted or adapted to fit by replacing the necessary components.

I think the answer to your question varies with every specific part and every specific truck and engine, transmission etc.

 

[INFChief]

No an expert but from what I understand, with wiring, the difference in engine harnesses comes down to v-belt vs serpentine and 4spd vs 3spd. As with anything else, as time goes on and they change design, the parts and connectors change too. An early glow plug harness for example is $50 and many buy it thinking it fits their truck only to be disappointed when they try to install it. There is NO replacement for looking it up in the TM's and getting the right stuff. In general the trucks all use the same basic design and nearly everything can be retrofitted or adapted to fit by replacing the necessary components.

I think the answer to your question varies with every specific part and every specific truck and engine, transmission etc.

I’m tracking with you. RE the $50 glow plug harness. When looking up parts for my 1097R1 I am using the UPC (useable on code) of AVY. And I certainly understand that on any vehicle there will be specific items such as generators, etc., that will vary depending on how that vehicle is outfitted with comm’s or other accessories. I spent the majority of my 21 years in the motor pool and am somewhat familiar with 998’s but have no experience with the RECAP and upgrading variants.

 

[springer1981]

I’m tracking with you. RE the $50 glow plug harness. When looking up parts for my 1097R1 I am using the UPC (useable on code) of AVY. And I certainly understand that on any vehicle there will be specific items such as generators, etc., that will vary depending on how that vehicle is outfitted with comm’s or other accessories. I spent the majority of my 21 years in the motor pool and am somewhat familiar with 998’s but have no experience with the RECAP and upgrading variants.

I have zero experience in a motor pool and only work on 1 HMMWV, mine, but I have added and changed a lot of things that "don't fit" my truck. I use 6 or 7 UPC codes depending on what I am doing. I see everything as "Fits" just depends on how much time, money and ambition you have.

 

[mgFray]

You will absolutely find 6.5L GEP w/ the 3-speed transmission. The vehicle may have originally come with a 6.2L, but at some point the engine was replaced and more or less all replacement engines were 6.5L GEP.

Basically if it has a 4-speed transmission it's PROBABLY a 6.5L. If it has a serpentine belt, it's a 6.5L.

If it has a V-Belts it could be either a 6.2L or 6.5L, and that is where you need to look and you can often tell the difference just by looking at the valve covers. (The sticker is different between the 6.2L and 6.5L GEP.)

 

[springer1981]

You will absolutely find 6.5L GEP w/ the 3-speed transmission. The vehicle may have originally come with a 6.2L, but at some point the engine was replaced and more or less all replacement engines were 6.5L GEP.

Basically if it has a 4-speed transmission it's PROBABLY a 6.5L. If it has a serpentine belt, it's a 6.5L.

If it has a V-Belts it could be either a 6.2L or 6.5L, and that is where you need to look and you can often tell the difference just by looking at the valve covers. (The sticker is different between the 6.2L and 6.5L GEP.)

The OP post was back in 2016... the rest of the conversation pretty much starts at the 2nd post as of today.

 

[mccullek]

The OP post was back in 2016... the rest of the conversation pretty much starts at the 2nd post as of today.

I have a M1097R1 and it has a 6.5L with the 3 speed.

 

[Ajax MD]

Not an expert but from what I understand, with wiring, the difference in engine harnesses comes down to v-belt vs serpentine and 4spd vs 3spd.

Negative. My truck was re-engined by the Marines in 2005. It received a 6.5L with v-belts and they left the 3spd in place.

 

[INFChief]

Negative. My truck was re-engined by the Marines in 2005. It received a 6.5L with v-belts and they left the 3spd in place.

Mine too.

 

[MarkM]

My 91 M998 went through a refit in 2008. Chevy 6.5 with a 3 speed and a NP242.

Mark

 

[mccullek]

My 6.5L also has the multiple belts with no serpentine option.

 

[springer1981]

Negative. My truck was re-engined by the Marines in 2005. It received a 6.5L with v-belts and they left the 3spd in place.

OK, so I'm not sure what you are saying "Negative" about. You have a 3spd wiring harness that fits a V-Belt engine (6.2, 6.5 does not matter). If you did a 4spd 4L80 conversion you can use the same harness and add an aftermarket TCM. However, if it was a factory 4spd the engine harness would be different to incorporate the 4spd wiring such as TPS and TCM wiring as well as a Serpentine belt.

There are different versions of the wiring harness and it comes down to v-belt engine, serpentine belt engine, 3spd or 4spd. What is "Negative" about that?

 

[mccullek]

I'm leaning to the idea that these "R1" rebuilds only got what they needed. Most were upgraded to the "heavy variant" and the 6.5L motor. The rest of the rebuild was dependent on condition of the unit most likely or maybe what they had on hand. If the transmission was in good shape or they didn't have the stock for the 4 speeds, they didn't change them out maybe? Probably the same with the belts. My M1079R1 was upgraded to the heavy variant and a 6.5L engine, but it still has a 3-speed transmission, and my belt is not serpentine.

 

[springer1981]

My 6.5L also has the multiple belts with no serpentine option.

As I understand it, serpentine belts are not an option. If the truck originally had a v-belt engine then the upgrade included the v-belt engine and maybe later a serpentine belt engine.

Your engine can be converted to a serpentine belt but you have to change all the pulleys and IMO it isn't worth the effort.

 

[mccullek]

As I understand it, serpentine belts are not an option. If the truck originally had a v-belt engine then the upgrade included the v-belt engine and maybe later a serpentine belt engine.

Your engine can be converted to a serpentine belt but you have to change all the pulleys and IMO it isn't worth the effort.

I agree, I wouldn't go to the trouble unless they start breaking regularly. No more than I drive it, good belts should last a long, long time.

 

[springer1981]

I'm leaning to the idea that these "R1" rebuilds only got what they needed. Most were upgraded to the "heavy variant" and the 6.5L motor. The rest of the rebuild was dependent on condition of the unit most likely or maybe what they had on hand. If the transmission was in good shape or they didn't have the stock for the 4 speeds, they didn't change them out maybe? Probably the same with the belts. My M1079R1 was upgraded to the heavy variant and a 6.5L engine, but it still has a 3-speed transmission, and my belt is not serpentine.

I suspect the primary reason for not changing the transmission is total cost or work to do it. changing the engine is simple. Going from 3spd to 4spd is new engine, transmission, engine wiring harness, adding a TCM, change transfer case, change driveshafts. Basically replace the entire drivetrain.

 

[Ajax MD]

OK, so I'm not sure what you are saying "Negative" about. You have a 3spd wiring harness that fits a V-Belt engine (6.2, 6.5 does not matter). If you did a 4spd 4L80 conversion you can use the same harness and add an aftermarket TCM. However, if it was a factory 4spd the engine harness would be different to incorporate the 4spd wiring such as TPS and TCM wiring as well as a Serpentine belt.

There are different versions of the wiring harness and it comes down to v-belt engine, serpentine belt engine, 3spd or 4spd. What is "Negative" about that?

Whoops, I missed the keyword "harness." I thought you said that those were the differences between trucks. My apologies.

 

[Mogman]

I'm leaning to the idea that these "R1" rebuilds only got what they needed. Most were upgraded to the "heavy variant" and the 6.5L motor. The rest of the rebuild was dependent on condition of the unit most likely or maybe what they had on hand. If the transmission was in good shape or they didn't have the stock for the 4 speeds, they didn't change them out maybe? Probably the same with the belts. My M1079R1 was upgraded to the heavy variant and a 6.5L engine, but it still has a 3-speed transmission, and my belt is not serpentine.

The 1097A1 was a heavy variant, when they rebuilt them only the 6.5L and the NP242 were available, all the rest is stock A1 from what I can see.

 

[Retiredwarhorses]

The Govt never converted a 3 speed to a 4 speed, trucks are repaired based on IROAN standards in the contract.
IROAN=inspect repair on as needed basis
A 4 speed gets a bit more than just an engine with a different engine Harness.