I was just wondering how difficult and how much it costs, because Im tempted to rebuild my tranny while im swapping engines. cost is the biggest factor, I would like to do it myself to save from paying through the nose at the local transmission place.

thanks, Brendan

I don't think any manual tranny is hard to rebuild, if you can get it all apart. I rebuilt one many moons ago in a D-50, and only needed bearings, syncros, thrust plates, and seals, and I think I spent about $100 plus lube. I don't remember having to have anything pressed apart/back together, which is the main stumbling block. All my bearings drove out of the case with a brass drift and BFH, and I used no special tools. There are some upgrades in the thrust plates and I think in the input shaft bearings available for later models that retro fit into the older case. I'd change the pilot bearing in the crank tail, too. Weak point of these trannies seems to be the input shaft assembly. I've seen dozens with a really floppy input shaft, on the order of 1" nose of the shaft deflection.

I've also seen a couple of 300k mile trannies that were tight as new (did need new syncros), but almost all of these had been run with atf in the box instead of gear lube. Draw your own conclusions.

interesting, I only have 116,000 on mine, and it still works great, but i hear slight noise in the gears such as 3,5 especially in 5th, I also hear noise on the back side of the gears.

Im not that worried about it, but I figured that while I had it apart, I could do it but maybe too many projects at once will be hard.

would a worn syncro make it hard to shift into some gears? sometimes its rough going into the lower gears. Is this something I should worry about?

I also just recently changed the tranny and transfer case fluids when I did my clutch around 110,000

Don't want to scare you...but, those were my symptoms before all hell broke loose in my 5-speed meltdowns. I had a noticeably noisier 5th gear on the way home from a trip, then a few days later, the magnitude of the noise became greater. In the days just before el destructo, the 'box was noisy on shifting into the lower gears, like I didn't have the clutch all the way in.

Someone (maybe Kevin C or Lizzord???) had some really good tips on specifically what was beefed up in the later models, as well as a couple of tricks to keep things from flying apart. I seem to remember something about a nut on a countershaft or something. (Obviously, I am not a real good mechanic or anything remotely close to one...). FastEddy has some really good tips; I would follow his advice to the "T". My gear lube is coming out and ATF is going in!

John B.

That should shift really smoothly on cold mornings..... provided the synchros last until winter.

I may be mistaken, but I don't think Eddy was recommending ATF for your manual transmission. Using it could eat up your synchros.

Some manual transmissions are designed for ATF (BMWs come to mind).... yours was not. Your manual says to use 75-85W GL-4....... best to stick with it unless you know someone who has been running it in an identical transmission without problems for 200k miles or more.

Just my opinion.....

Frank

how many miles did you have on that? mine doesnt seam like its that bad, just a slight whine in 5th gear. I know its what my brothers nissan pickup did before he had his rebuilt.

Follow my advice at your own risk.

It helps to think about how the m/t works to diagnose it by sound. I usually get some of this wrong, so chime in with corrections. Rotation comes in the input shaft, which spins on bearings on the upper shaft and in the front bearing retainer. It can be locked to the upper shaft via a syncro, or the syncro the other way locks it to a gear that spins on it and is engaged with the lower shaft, which is all one piece with 3(?) gears on it (the countershaft), and the gears on it engage gears on the upper shaft. 1st, 2nd, 3rd, and 5th work by the torque going to the input shaft, the gear that spins on it engaged with the c/shaft & gears, and by locking the appropriate freespinning gear on the upper shaft to the upper shaft with a syncro. All gears are always engaged, by only one set is locked together at a time and to the upper shaft which sends the torque out the rear. You get 4th when the gear to the c/shaft is freespinning, and the syncro locks the input shaft to the upper shaft, and thus to the output shaft. Reverse uses a gear train to reverse the rotation of the output shaft, and reduce the rotation rate.

4th is the quietest gear, because there's no gear reduction going on, just shaft spinning. The input shaft is also locked to the upper shaft, so any runout there is reduced. That's why I could drive mine home with a blown input shaft case bearing. Gear noises in 1,2,3 & 5, and ususally R are signs the bearings are going, or a thrust plate is too worn, allowing too much slop in the tapered roller bearings. Bearing preload (to keep the "cones" of the taper roller bearings tight, and the shaft aligned in the process) is controlled by shimming the thrust plates/bearings so that the tapered roller bearing cone slack is taken up, plus a hair. Once that tightness is lost, the bearings don't last long.

If you have the tranny out, or the engine, grab the input shaft and see if it moves in/out, and/or side to side, to any degree at all. You should have no in/out that you can feel by educated hand, and only perhaps .5mm side to side (that gets controlled by the crankshaft pilot bearing). Any more, and you need to fix it now.

If it starts making noise, I'd fix it now. It only gets more expensive to wait. Bearings, seals, syncros, thrust plates, and shims, are LOTS cheaper than shafts and gears, especially if you weld the input shaft to the upper shaft, or eat off the front end of the upper shaft, or crack the case, or....

Build it right, lube it right, and the 5spd will live quite a while behind a carb 2.6 or v-6, both of which only put out around 150-175 ft lbs of torque.

Archive, please!

John B.

Rear thrust plate failure symptom: the gear shift lever will move fore and aft when accelerating/deaccelerating. Eventually the transmission will jump out of gear. Would replace with the improved rear thrust plate anytime the transmission is opened up.

Thanks, Phil. I forgot that one.

The shifter moves because it's engaged with the shift rails, which have the shift forks bolted to them, and the shift forks are engaged in the grooves in the syncro gizmos. With the thrust plate worn, the shaft with the gears and syncros moves fore and aft as the torque is applied to the front and rear of the helical gears, and as the syncro gizmo moves, it moves the fork, rail, and lever.