MUA-5 Transmission Swap.

ImpulseRocket89
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MUA-5 Transmission Swap.

Post by ImpulseRocket89 »

The information below is courtesy of Ludacris2.0 on Isuzone, as well as some of my own experience mid-way through the swap.

Eyecon pointed out to me that the MSG-5H transmissions are pretty slim pickings down under, and so some alternative transmission choices would be helpful. Also, if you plan on building your car for more power, this is a great option for a stronger factory Transmission.

For starters, one thing that makes this an easy upgrade is that both transmissions share bell pattern, input/output shaft diameters and spline count, and transmission mount locations. This means that from a physical stand-point the transmission bolts right in.

As you can see in these pictures, the MUA-5 (also known as an MSG-5F according to others) is a much larger transmission in both case size, as well as gear size, and it also has much larger and sturdier shift forks.

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The biggest difference between the two transmissions that has to be overcome is the shifter. The MUA gearbox shift quadrant box has a longer arm to actuate the internals (I compared mine). It also sits perfectly level, while the factory Impulse MSG mounting surface is actually angled back, and the Impulse quadrant is similarly built on an angle to make it sit level.

This is how the stock Impulse shift quadrant sits without any machine work done. Notice that it is actually angled forward as it sits on the level surface of the MUA.
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According to Ludacris2.0: "There is about a 2" gap between the change lever mounting bracket and the trans mount. The manual lever that goes into the trans was also not at the right depth to properly engage all the gears. So I had a machine shop mill the case where the quadrant box bolts up."

This is the mounting surface after it was milled. "They made a cut that took almost nothing from the front and about .375 to .5 from the back. I cannot remember which. This resulted in the manual lever being at a good angle inside the the trans and the quadrant assembly being at an acceptable one externally."
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Then finally he stated that There was still a small gap of about .5 inches that was filled with nuts for spacers. Also the internal reverse shift lever was making reverse difficult so it was removed from the truck MUA and left in place on the quadrant box.

Here is said shifter spaced with nuts after machining.
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This is the internal reverse shift lever/inhibitor that he had removed.
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Finally, he noted the following.
Bolting it into the car was a little more difficult than the original. The dimensions are bigger and it is considerably heavier than the other. I used a 93 pickup 9.5" clutch and flywheel.(There may be sufficient clearance for a 10.25") And also used the 93 pickup slave cylinder. The only other mods where some light dremel work on the slave cylinder mating surface, a small notch on the detent spring plate, and notches on the front two bolt holes of the quadrant box. The shifter bolt pattern was slightly different between the two.

I have driven about 600 miles on the transmission without any major problems. Although shifting is fairly notchy. Cutting out the plate around the manual lever might fix this. Also I used the speedo gear from the original thinking that it would make the speedometer accurate. Its way off, 90mph on the dash reads 70mph on a garmin. The truck speedo gear would probably be more accurate. Revs at 70 are about 3200. And 1st redlines in the 22-25 range.


As far as the shifter pattern being slight different, it is. When you line up the bolt holes of the quadrant with the trans case you can see it. Although it is not much.

In my case I did not have to do any light machining/dremel work to the slave cylinder surface as I used the slave from said trooper. However, I will know more if I have to once I get it mounted. I will also check to see if the Impulse slave cyl. can possible be used without any mods. FWIW, I checked the old 10.25" clutch disc and PP I had laying around from the rodeo and the clearances are fine. (more torque holding capacity).

The speedo gear issue he had is actually not a problem. The early MSG transmissions used a 5 tooth drive gear in the transmission, while most later MSG/MUA boxes had a 6 tooth.

As my math has shown me, and also as Bugle relayed to me in another message, if you retain the 6 tooth drive gear, you simply need to swap out speedometer gears to a 20 tooth unit. Otherwise, you can swap over the 5 tooth drive and 17 tooth driven gear from the stock impulse box and get the same result.

As this picture shows, the trans mount bracket and speedo drive fit perfectly.
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This is a side by side of the Impulse Speedo drive and the VSS from the Rodeo that the trans came from. They swap out directly, and according to JLEMOND, you can even simply remove the top portion (plastic) of the VSS and it will function just like the stock impulse speedo drive.
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The Stock Impulse is a 17 Tooth gear, while the Rodeo mine came from is a 21 tooth. If I swapped out to the 21 tooth that it came with, my speedo would be off about about 2.5-3mph at 60mph, and read slow (I would only be going 57mph). Since Ludacris went with the 17 tooth gear with the 6 tooth driven gear, he is spinning the speedometer cable much faster, thus throwing off his speedo the way it is.


And just because I like showing off my stuff, this is a 4ZE1 with my frankenstein MUA bolted together.

Image
Last edited by ImpulseRocket89 on Fri Aug 17, 2012 9:06 am, edited 2 times in total.
1988 Isuzu Impulse Turbo.
2005 Ford Crown Victoria LX

RIP 1989 Impulse Turbo, aka "Rakete"
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Post by ImpulseRocket89 »

One other point I wanted to touch on was his mph reading in first gear, it is close but not accurate. If he was shifting at 6000rpm, mathematically speaking he would have been going 29mph (yes, sorry for all of my non-metric terms lol). There is a difference of 3mph vs. the standard transmission due to a difference in the gearing.

As quoted from my more recent post about my project;

The MUA-5 box has the following ratios: 1st - 3.767, 2nd - 2.248, 3rd - 1.404, 4th - 1.000, 5th - 0.809.

Compare that to the factory Turbo gearing and you can see the difference.
1st-3.431, 2nd-1.963, 3rd-1.364, 4th-1.00, 5th-0.775.

One thing to note is that the MUA gearing is fairly similar to the earlier JR non turbo transmission. If you plot both transmissions side by side at 7000rpm shift points, you will also notice that 1-2 on the MUA is 200rpm closer but 2-3 and 3-4 are a couple hundred rpm more widely spaced, while 4-5 is again a little more closely spaced.

The only other real speed change is in 5th gear. Since it is slightly shorter than the stock transmission, you go from a factory mechanical top speed of 140mph@6000rpm to 134mph@6000rpm

There are ways to make up for the changes in first and fifth gear and bring the car back closer to factory. The first and easiest way would be to run a 1" taller diameter tire (24.7"), which essentially gears it up 1 step, and while that gains very little in first gear, it restores the top speed almost back to factory, 139mph@6000rpm.

The other option, is a taller rear diff ratio. There are two Isuzu 10 bolt differentials out there that were taller than the 3.909, but both are extremely hard to come by, at least around here. There wasa 3.73 and a 3.42 (only here for 2 years in the early 80's RWD, 4spd manual, Diesel pickups).

The 3.73 ratio would more or less have the same effect as upping the tire size 1 inch, to 24.7. First gear is a whole 30mph, while top speed is now 140. (6000rpm)

The 3.42 on the other hand restores first gear almost back to normal at 33mph, and you see an increase on the top end to 153mph (6000rpm)

This is the reason I am having another axle swapped into the car, not only for the ability to run a better Limited slip - or have one at all because there are no rebuild parts for the stock one anymore - and also to give me a choice of gear ratios. Plus, I don't trust the isuzu corp. 10 bolt diff to last with the plans that I have.
1988 Isuzu Impulse Turbo.
2005 Ford Crown Victoria LX

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Post by Piazza_man »

Excellent write-up there. Thanks for clearing things up. This makes the conversion much less daunting.
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Post by Bugle »

Another way to do the shifter without modifying the box is to take the pivot ball holder off the original MUA shifter and make a whole new shifter. I really didn't want to have to re-use the original sloppy shifter.

There seem to be 2 types of shifter, mine came with the one with the steel housing for the pivot ball. So i don't know if you can pull the one with the alloy pivot ball holder apart this much?

This is what it looks like disassembled. The big bolt they put in the side is for the cruise neutral switch however it requires a normally open switch instead of the MSG normally closed one. Luckily I found one in one of my random MSG boxes at the front of the box. Geminis might have switches there too?
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Cut the end off the shifter shaft and made a U-joint thing from some SHS, made a new gear stick out of RB Gemini parts because I had them lying around but i'm sure you could use a complete gear stick off another car which would be less work, or just re-use the original piazza stick.
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There were enough bolt holes on the quadrant box to sufficiently attach some angle steel to the sides of it, made a frame to solidly mount the shifter to the box.
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Shifter feels so much better than the original one.


If using the original Piazza clutch & flywheel you need to use the Piazza throwout bearing, the Piazza pressure plate contact is a smaller diameter and it sits out further
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That's as far as i've got so far
Have to put new front and rear seals in and get a better condition gearbox mount rubber then i'll install it.
Last edited by Bugle on Sat Aug 18, 2012 12:21 am, edited 1 time in total.
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Post by ImpulseRocket89 »

Wow, I may have to hunt down that style of shifter for the MUA and follow your lead a little bit. My stock shifter is the neoprene ball instead of the alloy, so any alternative to that would be great.

What exactly did that pocket come from that you mounted the pivot ball in?

Thanks for the good pictures, I now have a good idea on how to potentially make mine work as well.

I might take apart the Rodeo quadrant and compare the actual lever arm/shaft with the Impulse one. If they are close enough to the same I may look into combining the Impulse shifter/brackets and shaft with a quadrant and lever arm from a shifter similar to your MUA if I can find one. What did your MUA box come out of? The reason I may try this route is, if you look at the picture in the first post of the Impulse quadrant mounted to the MUA before he had it machined, the quadrant is designed to sit angled back, not level like the MUA boxes. So, if the MUA/MSG quadrants can be frankensteined and the shifter bracket, arm etc can be swapped over with a tiny bit of work, it might be the best solution.


My only concern doing it that way, and with the setup that you built, is that the shifter bracketry and/or the shifter itself will sit up too high and protrude into the trans tunnel, or too far into the cabin. Let me know how it fits.

If not, I will follow your lead. I know I can get a T5 style shifter easily enough, and just cut off the ball end and swap over the U bracket for the shift linkage arm.

Something like this one. http://www.americanmuscle.com/t5-t45-mu ... ifter.html

^ that would be nice for the angled back shifters upper half, as the forward gears are a bit of a stretch for me sitting all the way back.
1988 Isuzu Impulse Turbo.
2005 Ford Crown Victoria LX

RIP 1989 Impulse Turbo, aka "Rakete"
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Post by Bugle »

The ball holder came from an RB Holden Gemini which is the Australian version of the US JT I-Mark. Had to cut the excess off and machine it down then screw it to an alloy plate. I had already made the gear stick a while ago as a direct replacement for the original gear stick but then I got the MUA. If I was doing it again i'd just source one of those T5 shifters or similar and cut the bottom ball off.

This box came from a TF Holden Rodeo ute, they seem to cast the build date into the gearbox which is 1992.

I looked at attaching the MSG shifter frame to the MUA quadrant box, it could probably be done by welding up some steel that bolts onto the quadrant box and has the mounts for the MSG shifter frame, but I really wanted a solid mounted shifter. The linkage arm would have to be shortened if done that way as you can see from the top down pic the MUA shaft is longer.

I've made it so the pivot ball sits slightly lower than the original shifter in relation to the output shaft, looks to me like it might be sitting a fair bit lower than the MSG quadrant box bolted to the machined MUA casing? If that fits i'm pretty sure this will.

Image
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Post by ImpulseRocket89 »

Bugle wrote:
I looked at attaching the MSG shifter frame to the MUA quadrant box, it could probably be done by welding up some steel that bolts onto the quadrant box and has the mounts for the MSG shifter frame, but I really wanted a solid mounted shifter. The linkage arm would have to be shortened if done that way as you can see from the top down pic the MUA shaft is longer.

I've made it so the pivot ball sits slightly lower than the original shifter in relation to the output shaft, looks to me like it might be sitting a fair bit lower than the MSG quadrant box bolted to the machined MUA casing? If that fits i'm pretty sure this will.
Well, no matter what my Alloy quadrant/shifter frame from the Rodeo won't be a viable option as it is all one piece and the effort would be ridiculous compared to finding a quadrant similar to the one you have. The quadrant itself on the Rodeo is much larger than the Impulse one and the version that you have.

As far as using the MSG frame, I was thinking of simply welding the extra bit of metal needed to reach on to it. The T5 shifter platform would fit on it either way ( I looked at this a while back when I wanted to replace the stock shifter on my last car ).
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Post by Bugle »

Couldn't you just cut the end off the one piece housing to turn it into pretty much the same thing as the earlier type? I'm guessing it would still have an oil seal on the shaft inside there or it would get filled up with oil.
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Post by ImpulseRocket89 »

Bugle wrote:Couldn't you just cut the end off the one piece housing to turn it into pretty much the same thing as the earlier type? I'm guessing it would still have an oil seal on the shaft inside there or it would get filled up with oil.
I will try and pry off the plastic access panel and have a look. The issue still remains that its quadrant is much taller than yours or the stock unit.
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Post by Piazza_man »

ImpulseRocket89 wrote:
If not, I will follow your lead. I know I can get a T5 style shifter easily enough, and just cut off the ball end and swap over the U bracket for the shift linkage arm.

Something like this one. http://www.americanmuscle.com/t5-t45-mu ... ifter.html

^ that would be nice for the angled back shifters upper half, as the forward gears are a bit of a stretch for me sitting all the way back.
Those T5 shifters look trick and look ideal for us tall folk. Can they really be altered to suit the MUA. Love to see the end result with one of those on there.
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Post by ImpulseRocket89 »

eyecon wrote:
Those T5 shifters look trick and look ideal for us tall folk. Can they really be altered to suit the MUA. Love to see the end result with one of those on there.
The alteration is simple enough. Cutting off the bottom ball end of the shifter and welding or having someone weld a bracket similar to the stock one on so it will bolt to the linkage. Other than that it would be a matter of drilling new bolt holes to mount it to the plate/bracket that the factory shifter mounts to (or building one to suit like Bugle did). Other work may be required for clearance if the factory stuff was used, but nothing too out of the ordinary (a little trimming maybe)
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Post by Piazza_man »

Good stuff. I also like the LED gear knob. Would suit the car's digital dash gadgetry.
Last edited by Piazza_man on Mon Nov 25, 2013 8:12 pm, edited 1 time in total.
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Post by Bugle »

ImpulseRocket89 wrote:
I will try and pry off the plastic access panel and have a look. The issue still remains that its quadrant is much taller than yours or the stock unit.
I'll measure the height of mine then see how much clearance there is to the floor when i've installed it so you'll be able to figure out if the higher one will fit
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Post by ImpulseRocket89 »

Bugle wrote:
ImpulseRocket89 wrote:
I will try and pry off the plastic access panel and have a look. The issue still remains that its quadrant is much taller than yours or the stock unit.
I'll measure the height of mine then see how much clearance there is to the floor when i've installed it so you'll be able to figure out if the higher one will fit
That works. It may just look taller than yours, but since I have never seen one for myself it could simply be my own eyes lol.

There is another item about this particular transmission that I wanted to bring to light that I discovered when I was looking at overhaul kits.

As listed on http://www.drivetrain.com/parts_catalog ... l_kit.html and another trans website there seem to be two of the MSG-5F used behind the Rodeo 2.6.

The site I linked shows two different versions of the overhaul and syncro kits.

1990-91 - "5spd, RWD, rear load - 62mm O.D. rear mainshaft ball bearing - 1st and 2nd synchro rings are single piece design"

1992-97 - "5spd, RWD, rear load - 72mm O.D. rear mainshaft ball bearing - 1st and 2nd synchro rings are multi-piece design"

This would lend to the idea that getting a 92-97 gearbox is the best route to go, as Isuzu seemed to make some imporvements in both the rear mainshaft bearing size as well as the syncro for 1st and 2nd gears.

The cost of the overhaul kit with the syncros is also quite a bit different in price between the two. The early 90-91 kit is only $203 while the 92-97 is $530.

In any case, if somebody does decide to do this transmission swap in the future it would be good to make sure you know which year range the transmission came from when ordering any parts.
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2005 Ford Crown Victoria LX

RIP 1989 Impulse Turbo, aka "Rakete"
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Post by ImpulseRocket89 »

Well I managed to get out to my garage (other side of town) and do a little work. I took the Alloy rodeo housing apart, and well, from underneath it looks to use the same shaft etc, so I could easily cut away that rear part of the housing to use it.

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The one thing it lacks though is the extra bolt holes to mount my own home made bracket to. I guess I could drill and tap a couple into the housing if needed.... The problem with that is, the metal for the housing is very thin, and where there are pre-existing holes they made it intentionally thicker.

It also has this odd tube vent thingy on it that I have no clue what its purpose is lol. It goes to the rear section, which is sealed off by a big hunk of white plastic.

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I decided to take a photo of the stock Impulse quadrant to emphasize the angle it was meant to work at. This is why the case has to be milled at an angle in order to use the stock Impulse shifter setup, if that is the route anybody wished to go.

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^If you hold it level like it would mount to the trans, the arm sticking out faces back at an angle, and wouldn't engage the shafts in the transmissions well or at all.

I know you said that the bolt is for the location of the neutral switch for the cruise control. Hopefully I can make it work in there. ( I didn't bother to check )

I think I am going to follow your lead bugle and start making my own bracket and modifying this housing that I have. my 3" cutting wheel should make quick work of it, and drilling/tapping a couple of holes is no big deal. A lot less work and cost than machining the housing, and even if it costs the same in the end I get a better shifter out of the deal.
Last edited by ImpulseRocket89 on Sun Aug 19, 2012 5:00 pm, edited 2 times in total.
1988 Isuzu Impulse Turbo.
2005 Ford Crown Victoria LX

RIP 1989 Impulse Turbo, aka "Rakete"
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