TR4/4A TR4 Gearbox Removal

[Geo Hahn]

Getting ready to pull the gearbox out of the TR4. I thought I saw somewhere a technique that replaced a couple of the bolts holding the bell housing to the engine with long threaded rods (decapitated bolts) that took the weight of the gearbox as it was slid straight back (and again when it is slid forward) making removable and installation smoother & easier. Good idea? If yes, how long should they be?

My assistant will be my wife so I'm interested in anything that make it easier to wrassle it out.

 

[Bob Claffie]

GEo, I've used that method on both a Mustang and a Corvette and it is slick. Length is governed by the length of transmission shaft. I think the threaded rod I used was somewhere around 8" long. When you do this you may have to jack up the engine to get a straight shot backwards followed by a two by four across the frame rails to hold the engine up while the tranny is out. Bob

 

[trboost]

Geo,
I have never pulled the grearbox on a TR4 but it should be very similar to the TR6. I have pulled the 6 trany many, many times, as a matter of fact it's out now for a Toyota 5-speed replacement.

I like to drive the car on to a set of ramps first. This makes it easier to get under the car to disconect the the slave cylinder & get to some of the bolts in the bell housing, although you can do most of it from above when you remove the trany cover. By raising the front of the car it also makes it easier the get a jack or brace under the oil pan. This is important because when you remove the trany the motor is balancing on the two front motor mounts & it will droop down making it difficult to remove & reinstall.

A clutch alignment tool will ensure an easier time when reinstalling. Keeping the rear of the motor properly supported so it is in line with the trany also makes this much easier..

The longer bolts or threaded rod you describe is generaly used when reinstalling the box. These are helpfull in aligning the bell housing to the motor.

 

[TRTEL]

George, I swear this would work for getting it out as I did on at least four occasions on TR3's though I won't say how long ago. Carefully jacking up the whole affair by the sump with a block of wood and a floor jack. Placed an old style wooden container for a case of soda upside down beneath the transmission. Then stack (cram)newspapers under the transmission. Lower the whold affair slowly until the papers are compressed. Then you can undo the bolts and slide that thing off yourself, even an overdrive unit. Unfortunately it does not work quite so well in reverse.
Tom Lains

 

[TRMark]

My advice would be to remove the drive shaft, especially if you are going to use the decapitated bolt thing. That would allow you to back the tailshaft down the tunnel and then forward to engage the alignment bolts when installing. My wife and I made two boys that is the extent our togetherness when doing projects; such as working on cars or hanging wallpaper. Good Luck!

 

[Alan_Myers]

Hi Geo,

Sorry to hear you are having to remove the gearbox to resolve the clutch issues.

I've never used that bolt alignment method when removing or installing the TR4's gearbox. But, it might be useful, particularly when re-installing. On TR4, originally there is one stud at the 12 o'clock position on the bellhousing, and that's all the alignment help I've ever needed. Yes, if the clutch and pressure plate are removed or moved in any way, an alignment tool or dummy input shaft to align the splines with the pilot bushing will make your life a lot easier when you go to reinstall the gearbox.

Once the interior bits are out of your way and the starter removed... yes, the driveshaft can be completely removed, but the front section might slide far enough back on the splined joint to make that unnecessary. Depending upon exactly how the exhaust system is run, some parts of it might be removed, too, for a little easier access. This might be unnecessary, though.

Others noted lifting the rear of the engine with a jack under the sump, which shoiuld be protected by a flat, wide piece of wood on top of the jack. This is actually mandatory to remove the gearbox, since you'll need to raise the rear of the gearbox before it will slide out. For easiest access, you'll probably want to remove the nuts and bolts around the top of the bellhousing *before* lifting the rear of the engine and tilting the gearbox up. The firewall will make it difficult to get to those bolts after the engine/gearbox have been jacked up a little. Once the rear of the gearbox is loose and you are ready to lift the rear of the engine, have someone slowly jack up the engine while you are watching the throttle linkage that goes across the firewall, right behind the engine. That's what limits how high you can jack the engine. You only need to lift the engine an inch or so. Just leave the engine slightly lifted until you put the gearbox back in.

Thankfully, the TR gearbox is not terribly heavy, about 70-80 lbs empty of oil for the non-OD unit, about 120 lbs with OD.

One suggestion, assuming it's an original "thin-flange" TR4 g'box in your car: When reinstalling the gearbox I personally think it's a good idea to replace all the various nuts & split-type lockwashers with nylocks or jetnuts and plain, flat washers on the gearbox side at least. This because the thin cast aluminum flange at the bellhousing can sometimes crack and break due to stress. It's a known weak point and was beefed up on later cars. IMHO, using larger diameter plain washers here helps to spread the stress around a bit and better support the bellhousing-to-engine mounting point. With plain washers, the nuts need to be self-locking, thus the nylocks or jetnuts. BTW, I opted to replace all the original bolts with good fitting Grade 8 sized so that no threads ended up inside any of the mounting holes. Probably overkill... but what the heck! /ubbthreads/images/graemlins/smirk.gif

Hope you find the clutch problem is easily resolved, once the g'box is out.

/ubbthreads/images/graemlins/cheers.gif

 

[Geo Hahn]

Thanks for all the tips & encouragement. Everything is now apart and supported except for the few bolts and nuts securing the bellhousing. Really came apart fairly easily (so far).

In the end I took the suggestion to undo both ends of the propshaft (yes, I remembered to index the orientations) to have maximum room to back-up the gearbox.

Now I know why so many TRs have a bent throttle linkage that some owners think they were originally that way. I didn't do it... but it would be real easy to jack the back of the block right into that sucker.

 

[Geo Hahn]

Thanks again... now that the gearbox is out the problem is obvious:

Those bits in the inset were in the bottom of the bell housing. Any suggestions on brands of clutch, etc would be welcome.

And yes, it did make some serious noise in the last moments of the drive.

 

[TRMark]

Ouch! That's pretty ugly. Since you have it apart, are you considering switching to a later clutch like the 4A? I did years ago.

 

[Alan_Myers]

Hi Geo,

Not too much to worry about, in terms of TR2/3/4 clutches. I think they are all pretty much the same and generally very reliable, although it looks like you managed to break one and all of them are pretty heavy. You won't have any of the fragility concerns that the TR4A & later, lighter diaphragm clutches bring with them.

I hope you'll replace at least the taper pin in the fork, safety wire it and possibly add an extra bolt to the fork as a backup, while you are in there.

One tricky thing is to properly install the throwout bearing. TRF offers them pre-installed on new carriers, if you have any concerns about doing it yourself.

Might want to reface the flywheel, while it's all apart. Might want to have it checked for balance, too. Might want to have the pressure plate checked for balance, too.

While the driveshaft is out is a good time to change out u-joints, if they are be needed. Might be a good idea to have it checked for balance, too. Be sure to at least use brand new nylocks on the driveshaft bolts, jetnuts would be even better and a new set of bolts as well would give some additional margin of safety.

There are other things you can do, while it's all apart, if you wish. You'll find quite a list of ideas in the archive, I'm sure.

p.s. Regarding swapping to TR4A/diaphragm cluth.... Like Mark, I swapped to the later one in my TR4. However, I did it to lighten things up, since I'm also running a lightweight flywheel. Also, clutch parts and flywheel for TR4A are cheaper than for TR4. But if you aren't changing the flywheel, there is some added cost of having the TR4 & earlier style flywheel drilled for the later clutch and you would definitely need a different throwout bearing, at the very least.

/ubbthreads/images/graemlins/cheers.gif

 

[Geo Hahn]

[ QUOTE ]
There are other things you can do, while it's all apart...

[/ QUOTE ]

Such as a body-off resto.

Yes, I will reface the flywheel and add that extra bolt. Thanks for the tip on the TRF bearing being prefit to the sleeve - I wondered why theirs was about 3X the price of the Moss part. I assume the 'tricky' thing here is that the bearing can get damaged if to much force is used?

 

[Alan_Myers]

[ QUOTE ]
[ QUOTE ]
There are other things you can do, while it's all apart...

[/ QUOTE ]

Such as a body-off resto.

[/ QUOTE ]

Sure, go for it! /ubbthreads/images/graemlins/grin.gif

[ QUOTE ]
Yes, I will reface the flywheel and add that extra bolt. Thanks for the tip on the TRF bearing being prefit to the sleeve - I wondered why theirs was about 3X the price of the Moss part. I assume the 'tricky' thing here is that the bearing can get damaged if to much force is used?

[/ QUOTE ]

Well, it's not so much a matter of too much force. Perhaps it would be better described as the wrong type of force.

The TR's TO bearing can pretty easily get warped and damaged when using the old "tried and true" method of installation... I.e., squeezing it onto the carrier with in a typical bench vise. Don't do that. That method has led to a lot of early failures of TO bearings on these cars. It's the pits to have to pull the gearbox again in 5K miles to replace a ruined TO bearing, for any reason! /ubbthreads/images/graemlins/frown.gif

TRF (and others) consulted with the bearing manufacturers and the problem seems to be that the bearing and/or it's housing get distorted when pressed on in the usual manner. The better and "approved" method of installation is to be careful that the bearing is pressed on straight, spread the pressure being applied as evenly as possible over the face of the TO bearing and, most importantly, rotate the TO bearing while it's being pressed on.

I seem to recall TRF also sells a special tool to install the bearing, that helps accomplish all the above. Buying one of those is an option (it's not fancy or expensive, last time I looked) if you prefer to reuse your TO bearing carrier and just want to buy and install a new TO bearing yourself.

A couple other things I'd suggest checking include looking for include any slop in the release shaft bushings, where it rides in the bellhousing. Your car probably has the early style bushings which are both greaseable and about twice as long as were used on TR4A & later (roughly 3/4" in length, as opposed to around 3/8" in length). Plus the early style bushings have a hole and grooves for grease, while the later style do not. The early type are more likely to be okay if they were given a little maintenance during their lifetime. Due to the smaller bearing surface and lack of grease, the later, "no maintenance" type are more prone to wear and much more frequently need to be replaced.

The release shaft itself should have grease zerks in either end. If it doesn't and has no tapped drilling for them, it might have been changed to one of the later "no-maintenance" shafts and the bushings might have been changed at the same time. I'd recommend always using the earlier, greasable version of shaft and bushings on any TR, although it requires the "extra effort" of a couple pumps from a grease gun every 12K miles or once a year. It's much more durable.

If you have reason to remove the release shaft from the bellhousing, that's a good time to check the hole for the clevis pin in the lever hasn't worn oversize. (It's the middle hole of the three, which all TRs should be using.) If it is, it can be welded up and redrilled, or alternatively a sleeve might be installed, both pretty easily done while the shaft is out of the car.

/ubbthreads/images/graemlins/cheers.gif