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Tranny swap

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gjh2007

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Hi all.

Looking for some advice. I have an extra tranny I picked up with a complete drive train a few years ago. Don't have any history on it at all.

Here is my question. My current gearbox grinds on a downshift to 2nd gear; a real pain coming into corners. It does also whine a little.

I drained the fluid & it actually looked pretty clean & am going to refill with GL4.

I doubt the tranny fluid will make the diff.

Now; I have the interior & drive shaft out on my car as we speak. The clutch has been operating ok, but I do have some wiggle in the cross shaft (infamous pin?)

Is there any way I can do a check on the extra box without installing it?

If I'm doing the box I will also do the clutch & cross shaft.

Awaiting your expert testimony.
 
I have heard really good things about "GM Syncromesh Fluid". It seems many owners have been surprised at how much of a difference it makes in manual shifting and it's ez on yellow parts, too.

Do a Google search...

For you fellas with Laycock de Normanville O/D's it's what Gear Vendors recommends in their Laycock-based add-on overdrives.
 
This may seem like a stupid question, but have you bled your clutch lately? I know what you're thinking, but make sure you have no air and that the slave is pushing the rod all of the way before you go any further.

With that being said, you will have to correct any play in the cross shaft sooner or later. How bad it really is will dictate the need for speed in the fixing.
 
The tranny oil should always look clean since it is sealed and doesn't share oil with another component like a Mini does.
It is the oil break down that you are concerned about.
Your grinding 2nd gear is more than likely a bad synchro. The whine is probably a bearing.
As for the backup unit, drain the oil and look for any metal floating in it. Put the tranny in neutral and pull the shift cap (8 capscrews). Spin the tail shaft while looking for any broken teeth in the gears. Look at your synchonizers for any noticable wear in the four pieces. The easiest way to do this is to look at 4th gear, since it should have the least wear, and base the other three on it.
Make sure the tail shaft spins freely and consistently. If it hangs up or the bearings make noise, it probably needs rebuilt.
You will want to make sure there is no heavy corrosion on the input shaft.
You can also look at the bearings in the engine for wear. Excessive wear on the rocker shaft or rocker faces will give you an indication on engine use. If the two have been together since new, you might be able to assume the wear on the tranny. But this is no guarantee.
If it appears to be good and you decide to use it, go for a test drive before you put the interior back together.
If the tranny comes out, it is always a good time to swap the clutch, unless it has been recently replaced.
 
Hi Gary,

Often one of the first indications of a broken dreaded taper pin is difficulty shifting into lower gears.

The reason is the clutch isn't disengaging fully. I'd check that out thoroughly before considering a gearbox swap. Your gearbox might be fine, with just a bit more wear on the 2nd gear synchro than the others, which is typical. It might be so little wear the garbox could go many thousands more miles without any work.

If you can induce *any* play between the cross shaft and the release fork, the pin is almost certainly broken and needs to be replaced (and probably would be best reinforced).
 
Oops! I missed the whine part! Sorry about that. Follow Doug's advice. And replace crankshaft pilot bearing while out.
 
I've been quoted as low as $150(Canadian)to replace the sychro bushings with the transmission out of the car.
If the unit is not whinning too badly, and you will have the trans out of the car, I might consider taking it to a local shop and get a quote.

Adam H.
____________________________________________________________
1973 Triumph Spitfire.
 
Thanks guys, always good to get an independent opinion, I am going to look a little further into the cross shaft, I just did a quick check; & yea I might as well bleed the clutch master.

As far as the fluids, I too have heard many things about the GL4, vs GL5 issues, besides the bad thing 5 does to the brass parts. Maybe synthetic? but I can do a good look at the extra box on the bench, including the cross shaft easier than the one in the car.
 
The transmission in your car is having problems so the logical thing to do is look to the spare.

I would make a visual inspection of the spare transmissions innards by removing the top as mentioned in an earlier post. I would also spin the shaft by hand through each gear looking for back lash and paying particular attention to the counter shaft movement for signs of needle bearing wear or failure. Then if all looks well, and given you already have the interior and drive shaft out, installing it should only take an hour, two at tops including a beer break. You can then start the engine and run it through the gears which while not under load, will tell you if it has problems.

Ray
 
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