J-mod on valve body = better mpgs?
Senior Member
Joined: Jan 2005
Posts: 266
Likes: 0
From: NewYork
I appologize also,
I did not mean to offend.
I used the example of the Mark because it has a bad reputation for this gear overlap. The transmissions are the same between car and truck, and under very similiar load due to vehicle weight and gear ratio. Before I go any further, yes I know that a 4wd has a different output shaft.
The overlap is a bad thing no matter what vehicle the transmission is in. It has been pointed out correctly that it DOES make the transmission generate more heat due to the slip= more wear.
People who say that the J-mod is a bad thing, quite possibly have either messed up the job themselves or know of another who has by drilling the wrong hole (unknowingly). It's a common mistake, with bad results.
After doing the reaserch on this mod, I found that it is what you are also instructed to do on an aftermarket shift kit install. They just dont call it anything. Thats if you dont buy the kit that already gives you a replacement plate, which already has the appropriate holes larger. The kits are not car or truck specific, they cover all which share the same transmission. If a kit is application specific in term of car or truck, then they are only giving you the peices to do one kind of build. Most kits allow you to decide how you want to proceed with an install. Weather it be HD truck and towing, street performance, or strip racing. EX. different spacers and or springs, but the all share the plate drilling proceedure, or replacement plate.
It's for these reasons that I'm not going to do a J-mod, but rather a shift kit, which improves more than just what a J-mod does. And no one says that a shift kit is a bad thing do they?
Add up the time and money, you might as well spend another $75. and get the full benifit, as well as the new gaskets you might need to do a J-mod anyway.
Lowflyingbird
I used the example of the Mark because it has a bad reputation for this gear overlap. The transmissions are the same between car and truck, and under very similiar load due to vehicle weight and gear ratio. Before I go any further, yes I know that a 4wd has a different output shaft.
The overlap is a bad thing no matter what vehicle the transmission is in. It has been pointed out correctly that it DOES make the transmission generate more heat due to the slip= more wear.
People who say that the J-mod is a bad thing, quite possibly have either messed up the job themselves or know of another who has by drilling the wrong hole (unknowingly). It's a common mistake, with bad results.
After doing the reaserch on this mod, I found that it is what you are also instructed to do on an aftermarket shift kit install. They just dont call it anything. Thats if you dont buy the kit that already gives you a replacement plate, which already has the appropriate holes larger. The kits are not car or truck specific, they cover all which share the same transmission. If a kit is application specific in term of car or truck, then they are only giving you the peices to do one kind of build. Most kits allow you to decide how you want to proceed with an install. Weather it be HD truck and towing, street performance, or strip racing. EX. different spacers and or springs, but the all share the plate drilling proceedure, or replacement plate.
It's for these reasons that I'm not going to do a J-mod, but rather a shift kit, which improves more than just what a J-mod does. And no one says that a shift kit is a bad thing do they?
Add up the time and money, you might as well spend another $75. and get the full benifit, as well as the new gaskets you might need to do a J-mod anyway.
Lowflyingbird
Last edited by lowflyingbird; Apr 28, 2008 at 01:23 PM.
Senior Member
Joined: Nov 2002
Posts: 1,490
Likes: 18
From: Indianapolis, IN
You can't mod certain years of the truck valve bodies because the setups on both the plate and the internal springs end up giving you really crappy results that you don't at all want to deal with.
Now, that said, on an 03 if it has the 4R7x series transmission, then you might be able to do these mods if the plate looks like the plate in the j-mod pictures where the holes are all present and hole number 11 isn't a slot instead of a hole.
It will work jsut fine in that case.
Darrin
Now, that said, on an 03 if it has the 4R7x series transmission, then you might be able to do these mods if the plate looks like the plate in the j-mod pictures where the holes are all present and hole number 11 isn't a slot instead of a hole.
It will work jsut fine in that case.
Darrin