M1028 gear ratio swap input

[Glockfan]

In my opinion, a correctly built 700R4 is the wiser choice over a Gear Vendors unit (hereinafter GVU) for the following reasons -

1.- GVU provides higher final ratio to rear axle only; 700R4 provides higher final ratio to both axles simultaneously
2.- An inadvertent shifting into 4WD while the GVU is engaged will cause drivetrain lockup and damage; no possibility of damage with 700R4
3.- GVU requires shortening of rear driveshaft with increased pinion angle; 700R4 does neither
4.- GVU is an add-on to TH400 which has a first gear ratio of 2.48; 700R4 has lower first gear of 3.06

My 700R4 was built by Bowtie Overdrive and is rated at 450HP and 450FPT. I sincerely believe it will handle the 250hp my P400 will throw at it.

To each his own. Just my 2 cents.

Mike,

I am going a slightly different route with mine. I know you have researched this extensively. I decided to go with the 4L80E instead of the 700R4. I made this decision because I found an "almost" free 4L80E ($200) and decided that any 4th gear is better than NO 4th gear. While all of this is taking place, I am adding the 203/205 "doubler" from Offroad Design. I love my NP205 case but the low range was anemic at 1.97:1. With the addition of the doubler, I will be able to have effectively a 4:1 crawl ratio which will help in the Rocky Mountains.

What were your reasons for not using the 4L80E? I am curious. I know from past experience with you that everything you do is well thought out and with good reason. I am interested in your opinion regarding the two transmissions.

 

[Sharecropper]

Mike,

I am going a slightly different route with mine. I know you have researched this extensively. I decided to go with the 4L80E instead of the 700R4. I made this decision because I found an "almost" free 4L80E ($200) and decided that any 4th gear is better than NO 4th gear. While all of this is taking place, I am adding the 203/205 "doubler" from Offroad Design. I love my NP205 case but the low range was anemic at 1.97:1. With the addition of the doubler, I will be able to have effectively a 4:1 crawl ratio which will help in the Rocky Mountains.

What were your reasons for not using the 4L80E? I am curious. I know from past experience with you that everything you do is well thought out and with good reason. I am interested in your opinion regarding the two transmissions.

Hey Glock - You can't beat an "almost free" 4L80E. You will not be dissappointed. The main reason I went with a 700R4 is because it is a "dumb" unit and does not require any electronics like the 4L80E does. Same reason I decided to continue using the factory mechanical fuel pump instead of converting to an electric lift pump. Same reason I decided to stay with the factory engine-clutch-driven fan instead of installing electrically-driven fans on the radiator. Same reason I chose to continue to use a mechanical injection pump instead of "upgrading" to an electronic IP. Just trying to make my truck as fail-safe as possible. In addition, the 700R4 is the exact same length as my TH400 and therefore no cross-member or drive shaft modification is necessary. The 4L80E has a first gear ratio of 2.48, whereas the 700R4 has a lower first gear ratio of 3.06, which I like. Since I did not have either a 4L80E or a 700R4, all of these things impacted my decision. But if you decide to use a 4L80E, heck go for it. And let me know if I can help in anyway.

 

[Glockfan]

Hey Glock - You can't beat an "almost free" 4L80E. You will not be dissappointed. The main reason I went with a 700R4 is because it is a "dumb" unit and does not require any electronics like the 4L80E does. Same reason I decided to continue using the factory mechanical fuel pump instead of converting to an electric lift pump. Same reason I decided to stay with the factory engine-clutch-driven fan instead of installing electrically-driven fans on the radiator. Same reason I chose to continue to use a mechanical injection pump instead of "upgrading" to an electronic IP. Just trying to make my truck as fail-safe as possible. In addition, the 700R4 is the exact same length as my TH400 and therefore no cross-member or drive shaft modification is necessary. The 4L80E has a first gear ratio of 2.48, whereas the 700R4 has a lower first gear ratio of 3.06, which I like. Since I did not have either a 4L80E or a 700R4, all of these things impacted my decision. But if you decide to use a 4L80E, heck go for it. And let me know if I can help in anyway.

Plenty of GOOD reasons. As I figured. There is something to be said about keeping it all mechanical.

 

[Recovry4x4]

Hi, I am new to the SS Site. I have installed the Axles from a CUCV in a Full size Blazer, so I am familiar with them.

My Question is will a CUCV with 4.10 Gears pull honest 38" Tires decently or should I hold out for one with the regular 4:56s?
Tires will be Michelin 325/85R16 XMLs . it was a Brush Truck for the Air Force and is a crewcab fire Truck, put in Service in 1988. It is the Square body style not the updated Civvy one

I appreciate any Guidance You may have.

12Bore

All the CUCV line except the blazer had 4.56 gears. If what I read is correct, you have a crew cab that was in military service and it has 4.10 gears. It should do okay but lots depends on the rest of the driveline. What engine and transmission is your 3+3 sporting?

 

[TheControlVoice]

In my opinion, a correctly built 700R4 is the wiser choice over a Gear Vendors unit (hereinafter GVU) for the following reasons -

1.- GVU provides higher final ratio to rear axle only; 700R4 provides higher final ratio to both axles simultaneously
2.- An inadvertent shifting into 4WD while the GVU is engaged will cause drivetrain lockup and damage; no possibility of damage with 700R4
3.- GVU requires shortening of rear driveshaft with increased pinion angle; 700R4 does neither
4.- GVU is an add-on to TH400 which has a first gear ratio of 2.48; 700R4 has lower first gear of 3.06

My 700R4 was built by Bowtie Overdrive and is rated at 450HP and 450FPT. I sincerely believe it will handle the 250hp my P400 will throw at it.

To each his own. Just my 2 cents.

I am also looking at the ones from Bowtie Overdrive. Which level did you go with and what else did you need to make the swap?