Transmission Upgrade for '81-'85 5-Speeds

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JoeIsuzu
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Transmission Upgrade for '81-'85 5-Speeds

Postby JoeIsuzu » Sun Sep 09, 2007 12:10 am

I'm trying to rewrite this into more of a true "how-to" guide. Consider it "under construction".
Introduction

This started with a "classic" post by JLEMOND. Others have contributed, and I will try to credit those whose posts are incorporated into this guide.

The MSG-5 transmission was redesigned for 1986, with a different countershaft, larger bearings, and a larger output shaft. This transmission is much more durable than the one used from 1981-1985. These transmissions are generally available for anywhere from $50-$250. At that price, and with the improvements, it is hard to justify rebuilding an '81-'85 transmission. An upgrade is a more cost-effective solution.

The following posts will cover:
Last edited by JoeIsuzu on Mon Apr 04, 2011 9:44 pm, edited 10 times in total.
Reason: Rewrite in progress...under construction...

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Sourcing your "upgrade" transmission

Postby JoeIsuzu » Sun Sep 09, 2007 12:10 am

Your upgrade transmission can come from any of several vehicles:
'86-'87 P'up (diesel or gas)
'88-'95 Pickup or Amigo (gas 2.3 only)
'86-89 Impulse (note that the Turbo has a higher 5th gear ratio)

This is from an old post, but I wanted to put it here, with the addition of the Turbo Impulse ratios. I think the info for the P'up/Pickup came from Jerry. The Turbo Impulse info came from from http://www.isuzuperformance.com/isupage/hist/specimpjr.html. I suspect there's a slight error on 2nd gear for either the "Gas" pickup, or the "Turbo Impulse". They should probably be identical, but I don't know which one is correct.

Code: Select all

       Gas      Turbo DSL     NON-Turbo DSL   Turbo Impulse
1ST   3.431       3.785          4.122            3.431
2ND   1.969       2.171          2.493            1.963
3RD   1.364       1.413          1.504            1.364
4TH   1.000       1.000          1.000            1.000
5TH    .855        .855           .855             .775

Below is a blurry shot of the speedometer and tach showing the RPM at 60 mph, with the turbo Impulse (.775 5th gear) and speedometer "corrected" (at an indicated 60, it's going 61 mph). RPM is just a hair under 2,300.
rpm_at-60-755-diff..jpg

Jack
JLEMOND wrote:ACTUALLY ALL 86 AND UP THRU 95 2.3 PICKUPS USED THE SAME TRANS THE MSG -5
89-91 AMIEGO,S WITH 2.3 ENG,S HAD THE SAME TRANS
88-89 ISUZU IMPULSE WITH 2.3 OR THE 2.0 TURBO ENG USED THE SAME TRANS, ALL FRT BELLHOUSINGS WILL HAVE TO BE CHANGED
ALLSO THE REAR GEAR RATIOS WERE ANYWHERE FROM 4.10 ON THE PICKUPS AND THE AMIEGOS,, TO 3.90 ON THE IMPLUSE , JERRY
Last edited by JoeIsuzu on Mon Dec 15, 2014 11:03 pm, edited 15 times in total.
Reason: Rewrite in progress...under construction...

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Sourcing your slip yoke

Postby JoeIsuzu » Sun Sep 09, 2007 12:10 am

Here is an old chart that might be helpful, but it's definitely not 100% accurate.
puttputtinpup wrote:Here are a few more available options where you might find the 26 count spine for the upgrade and will also have the small u-joint: I know they're still somewhat vague, but..
81-87 4x4
86-87 2wd & 4wd 2.3 gas 5 speed (not positive on the 2wd)
84-87 trooper (4x4) w/ 2.0, & 2.3 & diesel
any 4x4 yokes through 87
and…possibly 86-87 2.3 automatics.
The automatics from 88-95 were 2.6. The spline will work (26ct), but will have the large u-joint.
Just count the splines to make sure before going through with the swap.
Last edited by JoeIsuzu on Mon Apr 04, 2011 6:25 pm, edited 13 times in total.
Reason: Rewrite in progress...under construction...

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Re: Transmission Upgrade for '81-'87 5-Speeds

Postby puttputtinpup » Mon Nov 10, 2008 6:45 pm

I'll begin by stating a disclaimer. Your experience and circumstances may be different than mine, so I'll post basically what I had to do to accomplish this upgrade. Your situation may be different, but in any event, I hope you can benefit from this in some way!!




Transmission upgrade

1. disconnect battery
2. jack up truck so that there is 14+” clearance under rt torsion bar at front tire
3. place jack stands under the frame
4. drain the oil from the transmission by removing the drain plug with a 24mm socket or wrench
5. remove the drive shaft at the rear end using a 12mm wrench on long bed truck, remove the two bolts where the two pieces of the drive shaft meet at the bearing using a 17mm wrench/socket.
6. on LS models, remove the console using a Phillips screw driver, and unplug the wiring harness going to the gauges. Take off the shifter knob, slide the console off.
7. remove the rubber shifter boot, and pull up the smaller rubber boot exposing the 12mm bolts holding the shifter into place. Remove shifter. Make a cardboard cover and punch out holes for the bolts and cover and fasten down the exposed hole w/ the cardboard piece.
8. at the bottom side of the bell housing, remove 4 small 10mm bolts and the 14mm exhaust pipe brace bolt to take off the inspection plate
9. remove the spring attached to the clutch arm, remove the clutch cable by clamping a vise grip onto the arm, and releasing the clutch with brute strength, then the cable will slip off the arm. Ease off the clutch arm and take off the vise grip.
10. remove the speedometer cable and the back-up (reverse) light switch wires. Take the wire loose from the clamp at the top of the transmission. Place both of these out of the way.
11. support under the engine with a bottle jack and some 2x6’s Have the handle ready so you can adjust the height of the tailshaft later.
12. remove the bracket and transmission mount at the rear of the tranny. Jack up the bottle jack so it will clear.
13. lower the bottle jack so the tailshaft drops down to the crossmember.
14. using a 14mm socket w/ impact and a 14mm wrench, take out all the 14mm bolts. Using an extension and the 14mm deepwell socket, reach over the top of the transmission and remove the three 14mm bolts at the top of the transmission. Grab a 17mm box wrench, and place it on each nut on the front side of the starter. Take the impact wrench and remove the 17mm bolts and pull the starter back(forward) a little. Last, take the same 17mm socket and remove the last two large bolts at the bottom corners.
15. try to work the transmission back. If it’s stuck, begin with a large screw driver and get it started to separate. Then use a pry bar. Be careful not to bust the casting of the bell housing. You’ll know once it gives way. Lay down on your back you head pointed to the back of the truck. Raise your knees til they touch the transmission. Pull back on the transmission, then rotate the top towards the driver’s side about 70-90 degrees so the starter hump will miss the floor board. Pull the tailshaft back onto the cross member until the bell housing is clear of the flywheel. Drop the front of the trans to the floor by straightening you legs and knees go down. Spread your legs so the transmission hits the floor (onto some cardboard). Crawl out from under the truck, and then reach under and slide the transmission out.
16. Remove the clutch & pressure plate with a 12mm socket.
17. Pilot bearing comes out best if you take off the flywheel. I use a 19mm socket on my impact wrench. Take a blind hole puller, or pilot bearing puller w/ a slide hammer, and gradually tap out the old bearing.
18. install a new bearing by testing a socket just smaller then the bearing OD and will fit easily into the crank. Then get the bearing started with a block of wood and hammer. Then use the selected socket against the bearing to tap in into the crank then rest of the way.
19. remove clutch arm and set to the side. Remove the ball that the one end of the clutch arm is fastened. Remove the 6 bolts that hold the front cover on.
20. When taking the cover off, pay close attention to the direction the large cupped washer against the input shaft bearing. The outer edge of the washer should be touching the outer race of the input shaft bearing (cupped part concaved side of washer facing the bearing). You will be reusing the diesel input shaft cover, not the gasser’s cover
21. remove the flat split ring surrounding the input bearing. It will not have holes at the ends.
22. Place two pieces of 2x4 on the floor and position them so that the outer edges of the bell housing can rest on them when you…
23. Take the transmission and stand it up on the 2x4’s tail shaft up.
24. Use two Vise Grip C-clamps or two larger Vice Grips to clamp the center plate and the rear half of the transmission together. (if the transmission comes apart at the rear section, you will have to make two new gaskets rather than one).
25. Take a 14mm socket, extension and remove all the bolts You may need a screw driver to drive between the bell housing and the center plate and brake them free of each other. You may only need a leather mallet, or a rubber one to pop the bell housing a little to separate it at the desired seam. You may want to do this as you’re lifting slightly on the tail shaft.
26. Once the two parts are loose, you can lift he back section away from the bell housing and place it onto a clean piece of cardboard. If you’re using two complete transmissions for the upgrade, you’ll have to go through all this twice.
27. Clean up the diesel bell housing surface to be attached to the new transmission, and the front cover mating surfaces. Clean up the new transmission surface to be mated with the diesel bell housing. Wipe them down with a degreaser like carburetor cleaner or brake cleaner.
28. If you don’t know how to make your own gaskets, maybe you can buy a set. Viewing the pictures may help you in making your own. Check with Jerry Lemond. You may be alright by using RTV sealer only.
29. Place a light film of RTV sealer on both surfaces to be bolted together. Place the gasket on the bell housing half still sitting on the 2x4’s. Pick up the back half of the new transmission and carefully place it into the bell housing. Don’t let it break the seal between the tail shaft and the center plate. Start all the bolts back into the holes by hand. Don’t forget where the one goes with the little bracket that the clutch arm spring hooks to. Tighten them all up good and snug. Refer to your manuals for proper torque specs.
30. Remove the input shaft seal with a suitable tool. Reinstall a new one. It should be O’Reilly or Advance Auto seal # 1990. I paid $7.99 for one.
31. Clean out any crud that might have gotten into the front bearing area during the preceding steps. Install the retainer ring onto the input bearing. Place the concave domed shaped washer in the cover. The outer edge of the ring must touch the outer race of the input bearing. If it’s backwards, it will be putting pressure on the middle of the bearing. Convex side outward, concave side inward. TIP: I put some grease in the cover where the ring goes so it wouldn’t fall out while placing the cover on. Smear a thin coat of RTV onto both surfaces to be bolted together, TIP: Put some RTV on the bolts to prevent oil from leaking out. Tighten to specs. Install the ball socket for the clutch arm. Clean it up some. Smear some fresh grease on it.
32. Remove the throw out or release bearing from the arm. Remove the old bearing using your vise (or a press) and a socket just smaller than the bearing outer edge. Tap it out with a mallet.
33. Take the new bearing and place it onto the collar. Place small pieces of wood against both jaws of your vise and the collar& bearing between them. Crank the vise until the bearing is pressed all the way on. Clean off the old grease from the collar, and smear some new grease inside and on the little ears that rest on the clutch arm.
34. Put some fresh grease on the ball socket end of the clutch arm and reinstall the clutch arm by snapping the wire clip around the back side of the ball.
35. A TIP from Jerry: before reinstalling the transmission, take a drill bit slightly larger than the hole (17/64” I think) and drill out the dowel hole at the top flange of the bell housing. (facing the bell housing it will be the farthest hole on your left on top) This made re installation much easier.
36. TIP: Loosen the filler plug while it’s out of the truck, then snug it back up until you’re ready to fill it.
37. Swap your drive shaft yoke out to the new size if you haven’t done so already.
38. Reinstall the transmission, starter, and drive shaft. Fill with Jerry recommended 5W-30 synthetic oil. Hook everything up. And crank it up!!
39. I’ve heard Jerry mention to make sure you get the new shifter with the 2.3 gas transmission to be used with the upgrade. This may be the only time I disagree with Jerry. If I had to do it over again, I would swap out the square box/base holding the shifter, and use the old shifter. The reason is that the old rubber boot that seals off the hole isn’t tall enough to fit around the fat part of the shifter shaft (the black part about 1-1/4” diameter) On the newer shifter, the large diameter part of the shifter is higher up because in the 88-95 truck, the boot is taller. It is also square at the base, so it can’t be used in the older truck, which is round. Now, if the shifter ends are the same and have the same # of bolts in the cover, they may just interchange. My 85 trans had two bolts, and the 92 had three bolts. I have seen the older transmissions with the three bolt cover as well.
40. After my test drive, I’ve noticed that the speedometer is off, but not sure how much. I do know it is slow.
41. There’s probably something I’ve left out and there’s probably a better way to accomplish this task, but this is the way I’ve done it. Whichever way you do it, have fun….and do it before you get too old. :lol: I’m in pain! :wink:
1 my 92 5 speed.JPG
2 upgrade transmission & driveshaft from Joe.JPG
3 drain the oil 24mm socket.JPG
:oops: two # 3 pictures
3 driveshaft tools.JPG
4 drive shaft out.JPG
5 console comes out.JPG
6 console and shifter out.JPG
7 cover shifter hole.JPG
8 old and new shifters.JPG
9 new sfifter hole covered.JPG

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puttputtinpup
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Re: Transmission Upgrade for '81-'87 5-Speeds

Postby puttputtinpup » Mon Nov 10, 2008 6:55 pm

More pictures:
10 access plate removed.JPG
11 engine supported and one more bolt to go.JPG
12 clutch components out.JPG
13 the two meet each other.JPG
14 remove front cover.JPG
15 note the orientation of the concave washer.JPG
16 gasser bell off.JPG
17 pliers to maintain tail shaft intact.JPG
18 the input bearing retainer ring.JPG
19 cover off the diesel trans.JPG
20 another view of front half.JPG
Attachments
11 engine supported and one more bolt to go.JPG

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puttputtinpup
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Re: Transmission Upgrade for '81-'87 5-Speeds

Postby puttputtinpup » Mon Nov 10, 2008 7:01 pm

more pictures:
21 front half of new trans.JPG
22 making a new gasket for bell.JPG
23 new front cover gasket.JPG
24 get the disk the right way and put sealer on cover bolts.JPG
25 remove throwout bearing.JPG
26 she's out.JPG
27 pressing on the new one.JPG
28 tip from Jerry drill out dowel hole with slightly larger size.JPG
29 new yoke and old yoke.JPG
30 New shifter, but advise using original.JPG

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Re: Transmission Upgrade for '81-'87 5-Speeds

Postby puttputtinpup » Mon Nov 10, 2008 7:04 pm

THE END!
31 rear portion of diesel trans.JPG
32 front half.JPG
33 the weak link in the diesel 5 speed.JPG

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JoeIsuzu
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Transmission and engine removal

Postby JoeIsuzu » Thu Nov 13, 2008 8:58 pm

PLACEHOLDER

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trooper T/diesel
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photos of up-grade trans

Postby trooper T/diesel » Thu Sep 09, 2010 8:20 pm

hear yea go jack.
Attachments
SANY1733.JPG
SANY1732.JPG
SANY1731.JPG
SANY1730.JPG
SANY1729.JPG
SANY1727.JPG
SANY1726.JPG

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JoeIsuzu
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Speedometer Correction

Postby JoeIsuzu » Wed Nov 10, 2010 10:23 pm

Updated 6/2/2012: I learned today that SOME of the upgrade transmissions have a 6-tooth ring gear. If yours has this, use the 6x18 driven gear from your original transmission, and you should not need correction.

To find out, remove the driven gear from the housing (where the speedometer cable attaches to the transmission). The tooth count on older ones will be stamped on the shaft of the gear. Newer ones have it embossed into the end of the nylon gear. Your original should be labeled "6x18". That's an 18 tooth driven gear that's cut to match a 6-tooth ring gear.

If your "upgrade" transmission has a driven gear that has "6x"-anything, it also has a 6-tooth ring gear and you're in luck! Use your 6x18 driven gear from the old transmission, and no correction is needed. For example, the one I pulled from a '92 Amigo had a 6x20 driven gear. When we install that transmission, we'll just swap the 6x18 gear from the original transmission, and it will read exactly as before.

On the other hand, if your "upgrade" transmission has a driven gear with "5x"-anything (like mine, from a Turbo Impulse"), your speedometer will be off. For example, if you have a transmission with a 5x16 driven gear (that's what I had), your speedometer will end up reading 6.67% low. This is because:
  • Your original transmission had a 6-tooth drive gear, and a 18-tooth driven gear. That's 18 turns of the driveshaft to every 6 revolutions of the speedometer cable (or 3 turns of the driveshaft to 1 revolution of the speedometer cable).
  • Your upgrade transmission has a 5-tooth drive gear, and a 16-tooth driven gear. That's 16 turns of the driveshaft to every 5 revolutions of the speedometer cable (or 3.2 turns for every 1 revolution of the speedometer cable).
You COULD use smaller tires, but that would be like reducing your rear differential to 4.11--not good. So, why not just use the speedometer gears from the original transmission? Great idea, right? Not exactly. Remember, the output shaft is larger on the upgrade transmission (that's why it's an "upgrade"). The original drive gear is nylon, and there is not much "meat" in the center of it. However, one of our members (I'll have to find who, and give him credit) bored out the center, and filed a keyway in it, and used it on the new transmission's output shaft. I'm not sure how durable that will prove, but it's definitely creative, and it restores his original speedometer gearing.

The best solution for most of us is a Ratio Adapter like this.
speedometer_correction_gear.jpg
Ratio Adapter from PATCTRANS on eBay
speedometer_correction_gear.jpg (11.52 KiB) Viewed 34455 times

This is what Paul used for his truck after he swapped rear ends. If your P'up is like mine, the speedometer reading was off by about +1$ or even +2%...
JoeIsuzu wrote:When I drove to Charlotte for the meet, the Garmin showed 72-73 mph when the speedometer said 75. At an indicated 62, Garmin said 60. And at 100...just kidding. :lol:
So, rather than looking for a +6.67% adapter, maybe a +5% would be better. Note: mine needed about 12% to match to correct for the new speedometer gearing, because mine came from an Impulse and had a 5x17 gearset. So I bought a +11% adapter from patctrans, an eBay seller. Below is an excerpt from my correspondence with them:
JoeIsuzu wrote:By the way, the adapter works beautifully. Do you do custom ratios for customers? I know some folks who need +5%, but you didn't have that ratio listed.
And their reply:
We do make customs ratios for customers. The + 5% is $72.00 plus shipping and handling. Know their is a 4-6 week wait since it has to be customly made. If you have any other questions please don't hesitate to contact us again.
PATC

- patctrans

The other option would be to find a 6-tooth ring gear from a late-version MSG-5 transmission, and swap it. It has to come from a transmission with the larger output shaft, or it won't fit. The swap is easy, a snap ring holds it on the shaft (it has a key to keep it from spinning). Unfortunately, I don't have a list of which transmissions had 5-tooth gears vs. which ones had 6-tooth gears. There ought to be a part number for the gear, but when I was looking, I was unable to even confirm that it existed (and now I end up finding one :roll: )

Jack
Last edited by JoeIsuzu on Tue Jun 03, 2014 10:36 pm, edited 1 time in total.
Reason: Corrected name of eBay seller "PATCTRANS"