Jeep TB Conversion for 2gnt
The stock 2gnt TB is
52mm. The throttle bodies for 90�s Jeep
4.0L I6 are 55-60mm.More air means
more fuel means more POWAH!!!The good
news is that the Jeep TB can be modified to fit on our cars.
The donor TB in this write-up is for a 91-95 Jeep Wrangler,
Cherokee, or Grand Cherokee, but any TB from a 91-99 will work. I bought it used for $60 on eBay. If the donor is used then this mod is relatively
cheap � compared to having the stocker bored, or buying a bored TB, or buying a
billet TB. It is, and will most likely
remain, the cheapest way to get more air.
A new one will work but the costs are higher. Also, there are several outfits that offer 62mm bored Jeep
TBs. Here is a link with some good
aftermarket Jeep TB info:
If you need some serious air then here are a couple of links
for Jeep TB specialists:
I want to explain the 55-60mm range. The inlets(filter side) on all of these Jeep
TBs are 60mm, but some of them taper to 55mm on the outlet(manifold side). I don�t know for sure, but it may have
something to do with what year the TB is for and/or weather or not it was made
for an automatic or manual transmission.
If all you want is 55mm then hey that�s great�but fear not! If you want 60mm then you shall have
60mm. I found a great write-up on
removing the taper, and it turns out that the taper is easily removed �
creating a nice 60mm bore through the entire TB. Mine started out with a 55mm taper, but now its gone. Nothing left but a beautiful gaping 60mm TB
all the way through. Of course if you
can manage to find a true 60mm Jeep TB then you won�t have to bother with the
taper. Anyway - here�s the taper
There are some clearance issues. The Neuspeed bar � is a no-go with this TB.
It simply will not fit with a Jeep TB.
Also, there is approximately .4 inches
clearance to the hood after it is installed.
The IAC housing is the highest point.
The good news for those with � inch phenolic intake manifold spacers is
that the TB juts toward a strength channel, which could easily be modified to
allow a Jeep TB to fit.
One more thing before we get started. You�ll notice that the 2 TBs are kind of
backwards from each other. The IAC is
on the bottom of the 2gnt TB, but the Jeep one is on top. The throttle plates actuate in different
directions � clockwise vs. counterclockwise. The 2gnt TB has 2 very deep
mounting holes diagonally opposed, while the Jeep TB has a puny little 4-bolt
base. Don�t worry - really, it�s ok.
Ok, enough about size, cost, options, tapers, caveats and
funkiness - lets DO IT!
Remove all of the sensors as well as the butterfly plate,
throttle shaft, and spring from both TBs.
All of these bolts are Torx T20.
The bolts on the 2gnt butterfly plate may shear when you take them out �
the damn things are dimpled on the end.
Take your time and work them back and forth, like you would when tapping
You�re going to use the 2gnt throttle shaft on our
Frankenstein TB, so if the bolts do shear out � remove the remnants with an
Like I said, you need to use the
2gnt throttle shaft. However the slot
needs to be widened to fit the Jeep butterfly (green slot lines � upper
picture). I used a die grinder, but you
could use a Dremel with a cutting wheel as well. The slot only needs to be widened enough to fit the new plate. I
noticed a nice natural size marker on the 2gnt shaft � the bearing race
marks. If you make the slot as wide as
the bearing marks (green arrows � lower picture) the plate should slide right in.
�so that it looks like this.
You need to cut the spring seat
(marked in green) so that our 2gnt shaft will fit far enough to install the
butterfly into the Jeep TB. The seat is
made out of a hard plastic and cuts easily with a utility knife if you just
whittle thin chunks. That�s right, I
whittled it. I just thought that would
be the most precise way to do it. It
actually didn�t take that long. A good
reference mark to cut to is where the spring seat tapers to the shaft(line
marked in red). So long as you cut
enough away that the butterfly can be installed � that�s the real point. I kept checking my work as I got closer by
inserting the shaft and placing the butterfly over top of it.
�till I could see through.
The base plate on the Jeep TB
needs to be cut away so that our 2gnt throttle shaft can rotate freely to WOT
(wide open throttle). Remove the
idle-set screw from the Jeep TB cause it�s in the path of destruction. The section marked in red needs to be cut
away. It is important to note here that
you MUST keep the slot in marked in green.
Don�t cut that slot out of the picture because we�ll need to secure the
spring in there. It�s also important to
note here that you MUST keep the last nub outlined in yellow. This is where we need to install the
idle-set screw. The safest way to go on
this one is by the eyeball and testing along the way. Cut enough away so that you can slide the butterfly plate into
place. Make sure you have free and
clear travel to WOT on the throttle shaft with the butterfly installed.
It should look something like this
when you�re almost done.
Our new TB is going to use one
Jeep spring. The stock Jeep spring is
actually 2 springs banded together.
Remove the band and separate them, cause we only need one.
In the next step we�ll be
modifying the 2gnt shaft to fit the Jeep spring. The modification looks a bit hokey at first, so I�m going to
explain the reasoning before we jump into it.
I actually had a lot of problems with getting enough spring
tension. The 2gnt TB comes with 2
springs, like the Jeep. The 2 springs
together were too thick to fit, so my first spring attempt was 1 of the 2gnt
springs, but it was too weak. It
wouldn�t return to idle after it was installed. So I looked to the Jeep spring.
It worked fine at first when I was just kind of cruising around. But the first time I really mashed on it all
of the sudden it wouldn�t return to idle easily. Turns out that the whole spring wasn�t effective � only part of
it because its smaller in diameter than the 2gnt spring and it was binding up
on the 2gnt spring seat. Look at the
springs/spring seats side by side. The
Jeep spring is thicker and smaller in diameter. You could also just go buy a bunch of springs until you find a
setup that works. Personally, I felt
compelled to source as many parts from the stock and donor TB. My conundrum was 2 springs don�t fit and one
2gnt spring is way too weak I was left with 2 choices � use the jeep spring
seat on the 2gnt shaft, or modify the 2gnt spring seat so that the Jeep spring
fit loosely on it. I chose to modify
the 2gnt spring seat. You can probably
cut the 2gnt spring seat down to the point where you can install one half of
the Jeep spring seat on the 2gnt shaft�but I chose to modify the 2gnt spring
seat � and it works great. So there you
So, we need to cut the spring seat
down so that the Jeep spring fits loosely on it. You�ll have to cut off the entire outer circle of plastic and then
just a little bit of the radius beams.
Again, it�s this hard plastic that can be cut pretty easily with a
utility knife. At this point it will
become blindingly obvious that the Jeep spring is backwards. What I mean is that instead of the spring getting
smaller when the throttle actuates, it gets bigger. I�ve been running this setup for a few of weeks now with no
spring tension problems. You�ll be done
when you can easily slide the spring onto the newly cut seat.
At this point, it should start
looking more like an actual TB. Please
disregard the fact that I�m using the 2gnt spring in these pictures. Like I said � I had spring problems.
Remove the 55mm taper if you want
to. I did it with a rotary file on a
drill press. Big ol� whoppin 60mm TB all the way through. Ahhhhh.
Follow the link at the top of this write-up for more detailed
instructions on how to do it.
Moving right along. The bolts on the 2gnt TB are way to long to
work on our puny little Jeep base.
You�re going to need to buy M8x25 1.25 pitch Allen head bolts for
mounting the new Jeep TB to our intake manifold. It�s very important that you get Allen head bolts because after
you make the new mounting holes in the Jeep TB, there will be NO room for a
regular hex head. The mounting holes on
the 2gnt TB are just about 3.3 inches apart center to center. That falls just inside the edge on the Jeep
holes. You need to drill new holes that
are essentially centered over that imaginary 3.3-inch mark inside the edge on
the Jeep holes. I used a 21/64th
inch bit in a drill press. It worked
ok, but I did have to ream the holes a bit to get the bolts to actually screw
into the manifold. When you�re
fitting/reaming the TB to the manifold, make sure you ream equally on both
holes. There really is not a lot of
room from the edge of the hole to the housing by the time it fits.
You can use the 2gnt Throttle Position Sensor just like it is.
The Idle Air Control motors look pretty
much identical, but the tips are different.
You have to use the 2gnt IAC motor with the tip from the Jeep. The tips screw out. They�re in real tight, but they will
unscrew. Take note of the tip height on
the 2gnt sensor before taking it off.
When you install the Jeep tip on the 2gnt IAC, set it to the same tip
height. I did, and it seemed to work
very well (it idled properly the first time I fired it up).
One of the great benefits of using
an OEM throttle body is the beautiful fitment of the butterfly plate within the
bore. You�ll notice that when the
throttle plate is shut, even if it is shut lightly, the plate will stick into
the bore of the TB. It�s a perfect
fit. When you crack it open feel that
it�s stuck and you can hear it click getting unstuck. The fitment is nice, but the sticking has to go. That�s why the stockers have idle-set
screws. Their purpose is to NOT allow
the plate to stick in the bore when it closes. They need to be set to stop throttle shaft rotation just before the
plate sticks. The reason is that, if
you let the plate stick � off idle throttle response feels jumpy. It turns out that a �-20 hex head bolt fits
the job perfectly.
Use a 13/64th drill bit
to drill a hole in the nub we saved from our initial base plate work (the nub
that was outlined in yellow). It needs
to be pretty close to the outside edge. Leave enough material to support a threaded bolt. Then tap the hole with a �-20 tap. Run a nut on to your �-20 bolt � we need it
to lock the idle-set screw. Then
install the idle-set screw. Set it to
where the butterfly no longer sticks into the bore of the TB and lock it in place
with the lock nut.
One fairly drastic difference
between the 2 throttle bodies are the idle air channel. The 2gnt TB uses a secondary port on the
manifold where the Jeep uses a plate bypass. You need to plug the idle port on the manifold or else you�ll get mad
vacuum leak and idle at 4000 RPM. The
idle port on my 95 Eclipse RS manifold is a � inch big. I�m not sure if all of the holes are the
same size on all of the years of 2gnt so please measure yours before buying a
plug. Since mine was � an inch, I got a
� inch button plug. Spread silicone on
the lip of the plug and plug the hole. Shove it in there firmly and wipe off the excess silicone so it doesn�t
get onto the gasket material when you install the TB.
Which brings me to the
gasket. I used 1/16th inch
thick gasket material to make the gasket.
It needs to be at least that thick because of the plug. The head on the button plug I used is not
exactly thin. I needed to use a thick
gasket material in order to get a good seal to the manifold. You can see the dimple made by the button
plug in this picture.
>We�re almost done. Take the assembled TB - latch it onto the
throttle cable and bolt it up to the manifold with the gasket in place. Hook up the sensors. I know you want to fire it up but first
you�ll need to adjust the throttle cable.
The shaft on the Jeep TB is a little further away from the intake
manifold than the 2gnt stocker, so you�ll most likely need to adjust the cable
a little. What you want to do is make
sure that the throttle shaft clicks nicely onto the idle-set screw just like it
would if you were holding the TB in your hand.
Even when you test it for very small openings, like with a nudge, it
should still click when it shuts. If it
doesn�t click then the throttle cable is still to tight, loosen it up.
Ok now, LET IT RIP! What else can I say here? It should work like a charm. If it doesn�t, then you messed something up
� check your work.
Other than that - You could ream the intake manifold out to match the new bore capability. I haven�t done that yet. The manifold inlet is somewhere around 55-57mm stock. I�m sure I�ll get around
to match it up to my new TB at some point, probably sooner than later. I�m N/A right now. I do have other air flow mods � cheapo eBay short ram intake,
drag cams, ported exhaust manifold, test pipe, and a GS-T exhaust. The power I got from upgrading to the Jeep
TB definitely noticeable. I won�t get
into the numbers because everyone�s setup is different, but I will say that I
couldn�t be happier with the results.
Inarguably, for our cars, a TB
upgrade is a good thing. 52mm just doesn�t quite cut it. How much bigger
is up for debate. 55mm may be good for
you. If it is don�t touch the
taper. Maybe you want 57 or 60mm? Well
then go nuts with the taper. You may
want a 62mm bore job for a racecar. It�s
doubtful at this point that a 68mm TB would be considered as anything other
than overkill but there are aftermarket billet Jeep TBs of that size � and they
could be fit to your 2gnt. Who knows �
If Gary ever builds that aluminum race block, someone may actually NEED a 68mm
TB.How much bigger is up to you and
I purchased a spare 2gnt TB to do
this mod, but I can sell mine now that I don�t need it anymore. I wanted to make sure that the mod would
work and was worthwhile before tearing my original TB to shreds. Really the only things I HAD to buy were the
Jeep TB, 2 M8x25 1.25 pitch Allen head bolts, a � inch button plug and the
gasket material�. because it does work, it is worthwile, and I already had all
of the tools to do it.
Oh I have to mention this - even a used one looks pretty tight after a bit of polishing with the Dremel.
Note: The part number for the 1991-1995 Jeep Grand Cherokee 4.0L Throttle body is 53030844.
The picture shows 53030846 which is the IAC housing and may be confusing if you are shopping for a throttle body.
Last modified on 2009-02-06 17:52:34