52 replies to this topic

[Spider]

Just before jumping to the conclusion of the baulk rings, which I did a few years back when finding gearboxes were 'dragging' when fitted with new baulk rings, when digging deeper I found the issue was how the case had been machined. Since then, I've been measuring all gearboxes and found them to be the issue.

 

More here;-

 

http://www.theminifo...st-baulk-rings/

 

while that particular thread is in regards to crunching, the cause will give similar results to what you are seeing - it sounds like the gearbox is dragging and most likely on 3rd or 4th gear.

[big john]

You can see on these two pix that there is a .013" difference. Put two of the thick ones in and that's over .025" and the syncros are butting up against the hub. No idea where thes thick rings came from, they were provided by my friend. I don't know why the pix are upside down, but you get the gist of what I'm saying.

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[Its a min]

Just before jumping to the conclusion of the baulk rings, which I did a few years back when finding gearboxes were 'dragging' when fitted with new baulk rings, when digging deeper I found the issue was how the case had been machined. Since then, I've been measuring all gearboxes and found them to be the issue.

 

More here;-

 

http://www.theminifo...st-baulk-rings/

 

while that particular thread is in regards to crunching, the cause will give similar results to what you are seeing - it sounds like the gearbox is dragging and most likely on 3rd or 4th gear.

 

Hi Moke Spider,

 

Thanks for this. I'll check what casing I have at the weekend, If it is the casing, what needs to be done to rectify it? I appreciate it will probably not be a DIY job but any help in pointing me in the right direction is appreciated.

 

Cheers again.

 

You can see on these two pix that there is a .013" difference. Put two of the thick ones in and that's over .025" and the syncros are butting up against the hub. No idea where thes thick rings came from, they were provided by my friend. I don't know why the pix are upside down, but you get the gist of what I'm saying.

 

Hi big john,

 

Thanks for the pictures. The difference is quite clear and I'm kicking myself for not thinking about double checking before it all went back together again.

 

Stef.

[russo]

Yip, I agree, unfortunately there is no way I would have carried on the assembly process if the gearbox was hard to turn, then was the ideal time to sort the problem. Unfortunately I think there is no alternative but remove and dismantle again. Sorry.

[Its a min]

Hi everyone.

 

Just a quick update.

 

So, the engine came out and gearbox split from the block. On dismantling the gearbox, the culprit became apparent. It looks like it was the mainshaft double bearing (AAU1365) which was supplied in the A+ rebuild kit from Minisport. When I removed it and compared it to the original one (luckily I kept it), it was over an 1/8" deeper and pressing up against the gears so, this calls for a quick trip to Minispares tomorrow.

 

One question though. I measured the gap in the laygear and a .008 feeler gauge fitted in snuggly. The thrust washer (marked DAM3180) measures .1218 on a micrometer. I remember reading somewhere on TMF that the gap should be between .002 and .006. My thinking is that if I get the DAM3182, which is .127 to .129 thickness, this will take me close to the .002. Would this be too little gap? In which case, would I be better going for the DAM3181 which is .124 to .126?

 

Cheers.

[Its a min]

What gearbox casing do you have?

Hi Moke Spider,

 

The casing is DAM5620.

[Retroman]

   You should send the supplier of said  'bearing'  a large bill tied to that pile of monkey metal. Its not good enough

 

One of the lads who worked there came to me for bearings....

[Retroman]

The endfloat is a bit tight at .002"

 

You can take some from the back of the thrust washer using a flat surface and some wet and dry

 

Takes a bit of effort but worth doing

 

If you are posh an engineer can surface grind it down a thou or 2

[Its a min]

The endfloat is a bit tight at .002"

 

You can take some from the back of the thrust washer using a flat surface and some wet and dry

 

Takes a bit of effort but worth doing

 

If you are posh an engineer can surface grind it down a thou or 2

 

Thanks Retroman.

 

It makes sense. Flat surface, wet and dry and some elbow grease sounds good to me.

[Retroman]

Never found any stock of elbow grease....hahha

 

Guess its like common sense,  rare

[Spider]

I agree with the Retroman, 0.002" is too tight. I generally aim for 0.003 to 0.006", There's little point in setting them too tight.

 

 

 When I removed it and compared it to the original one (luckily I kept it), it was over an 1/8" deeper and pressing up against the gears

 

 

OK, this can be deceptive as the Outer Track of these Bearings has changed a bit over the years. It really needs to be checked / measured from the Inner Race that butts up against 1st Gear Inner Bearing Sleeve to the Circlip Groove on the Outer Track.

 

 

 

What gearbox casing do you have?

Hi Moke Spider,

 

The casing is DAM5620.

 

 

OK, some of these I've found have issues. There's a link in post 16 ^ in this thread.

[Its a min]

Hi Moke Spider.

 

I measured the two by lining up the circlip groove, with the aid of the circlip fitted to one of them, to the edge which butts up against the gears.

 

I'll try and get some pics but there was definitely over 1/8" more bearing which in turn was pressing up against the gears.

[Spider]

Min,

 

Cheers - WOW !!!

 

Yeap, that would do it !!

 

What brand is on the bearing?

[Its a min]

Min,

 

Cheers - WOW !!!

 

Yeap, that would do it !!

 

What brand is on the bearing?

 

Hi Moke,

 

Can't make out the etching on the Minisport bearing but can just make out 'KOR' so I'm assuming it's a cheap Korean one.

 

But, I went to Minispares and got myself a new RHP bearing. When I got home and measured it up, it's exactly the same size as the Minisport bearing i.e. 1/8"+ deeper than the original when measured from the circlip groove to the edge which butts up against the gears. Does anyone know if the design was changed at anytime to fit a different cast casing for MPI's/SPI's? There is a distinctive larger space between the two rows on bearings on the inside of the cage holder which explains the larger size.

 

On the positive side (you have to be positive, right???) at least it wasn't a waste of money as the Minisport bearing fell apart when I was dismantling the gearbox despite it only being fitted for a less than a month and probably 2 miles use. Didn't get a chance to get photo's but will try and get some of the three bearings in the next few days.

 

One other thing I have noticed, but probably doesn't make any difference, is that the original bearing had 11 slightly larger ball bearings fitted instead of the 12 smaller ones fitted to the two new ones. Unfortunately, this means I can't rebuild the original bearing using donor parts from the new.

 

I'll update on progress when  I get a chance to start putting it all back together.

 

Cheers.

[Spider]

Hi Min,

 

I dug out some Bearings, some old (very old) up to the latest to measure

 

 

 

 

 

 

I measured from the 'business side' of the Inner Race, to the 'Business side' of the circlip groove;-

 

 

 

I got a range over 5 bearings from 0.797" to 0.827" - a range of 0.030" over these bearings, keeping in mid these were all used bearings, so there maybe some wear, but they all still felt 'tight'. Also, I've measured these 'unloaded' (ie, without the 2 inner races being clamped up) so I suspect, when clamped up, these variations would come down a long way.

 

Just looking at the part numbers for this bearing from 1969 to the present day, there has been a few changes in these over that time, the first being 11MDJT1G, then a 3/MDJ1N, then a 1/MDJ25.4N (which looks to be just a metricated number of that previous), a CDU 1479, AAU1365etc etc, so apart from a metrification of the numbers, I'm unsure as to what the difference between them is, however, I have fitted these latest Bearings to everything, from the earliest to the latest, usually without issue, though I have ground a few (thinned the inner race) prior to cutting shims as needed to space the bearing closer to the Final Drive Pinion, usually only needing 0.020"

 

Coming back to your Bearing, at 1/8" (0.125") difference, that's HUGE and really has me scratching. Are you able to post up a photo?

 

I've come across the KOR brand Bearings, they are ~ OK ~ but there's no way I'd fit them in to a Gearbox!

 

 

 

 There is a distinctive larger space between the two rows on bearings on the inside of the cage holder which explains the larger size.

 

 ..........as the Minisport bearing fell apart when I was dismantling the gearbox despite it only being fitted for a less than a month and probably 2 miles use.....

 

I'm just wondering here if the 2 inner races are actually and properly clipped together?

 

As I think you've found out, the Inner Race is actually made up of 2 Races and they have a C shaped spring clip that holds them together.

 

Also, in regards to the Bearing 'exploding' you'll likely find on disassembly, with the late Mainshafts, all Bearings will do this. The Bearings are an interference fit on these shafts (quite so) and so they are difficult to budge off the shaft once fitted. On disassembly, in the normal way, it's necessary (as you are aware) to slide this Bearing down the Mainshaft in order for the remove of the Shaft itself from the Box.

 

The early and early A+ types were a 'slide' fit. I found no issues from this type of fitment. Nowdays, with these later shafts, I take a lick off them with a diamond lap so the Bearing is a neat slip fit, no more exploding bearings.