P51 rebuild Step by Step.

[RT104GT]

Hi guys.
Many discussions on these pages about the relative merits of W50 vs P51 gearbox, to the extent that I chased up and procurred a genuine P51 to make my Corona GT "authentic" after we changed gearboxes in 1979 following a catastrophic failure of the main bearings.

The gearbox pictured below slowly has become noisy and whining (like me) and so we pulled it out after securing the P51 box off ebay for $140 and also buying a spare cluster off Dave just in case.


Funny thing about gearboxes as you will see from the photos.

I have owned a GT for 30 years and thought I was driving around on a W50 box for 25 years.

Funny about that.


For all intensive purposes you cannot tell the difference between a W50 and a P51.



TADAH its a Gearbox


5th gear and REV selector Fork


REV/5th with rear countershaft and main shaft bearings and the brake band of a Porsche syncro.



REV Idler gear the Counter shaft and 5th gear.




REAR VIEW

[Mr_Toyota]

P51 came out of a GT corona...anything else they where in?

Just curious...haha

[RT104GT]

P51 came out of a GT corona...anything else they where in?

Just curious...haha

RA25 GT like River owns and then discontinued in favour of the W series.
Maybe in most of the early GT's,
Very hard to find out any information.

I use a Celica handbook/workshop manual for disassembly procedures.

[RT104GT]

Question for the gallery, what is the best method to assess if the rollers bearings need replacing, how do you gauge side play and decide whether to replace or not?

[oldcorollas]

look at the surface of the rollers themselves and the races they run on. if there is any doubt, replace.

[river]

Hi,

If you're rebuilding the P51 then replace all bearings and rollers etc. The box is old, probably been sitting unused for god knows how long, and you don't know how many miles it's done, nor how hard a life it has had. Basically, it's an unknown quantity and while you've got it apart it's best to get all bearings changed.

seeyuzz
river

[RT104GT]

This happened this morning.



Main cluster assembly case removed.




Celica cluster identical.



YUK




Bellhousing is marked 18R 20R showing that these gearboxes were fitted to the US SR5 maybe?




Bearing set is available for $200



This box is in good nick, just the front bearing has flat spotted due to standing and rust.


WARNING ABOUT THE DIAGRAM IN THE REBUILD BOOK. FWIW


The retainer shown in the P51 example is shown in the reverse sense ( Its around the wrong way) and has the bolts going in the incorrect way, they go in from the front as yo can see in the photo above.

[RT104GT]

Hi,

If you're rebuilding the P51 then replace all bearings and rollers etc. The box is old, probably been sitting unused for god knows how long, and you don't know how many miles it's done, nor how hard a life it has had. Basically, it's an unknown quantity and while you've got it apart it's best to get all bearings changed.

seeyuzz
river

I am rebuilding the box I know the one I drove all these years.
Once the bearings are done it is a known quantity.
The needle rollers are fine and the box has not failed.
The other one is a contingency spare like yours.

I ordered bearings and circlips for $200 here Monday and the second to last set of rebuild gaskets for a W50/P51 from Toyota Altona here Monday $110.00

The suck it and see test is..
Start your engine, let it idle and let the clutch out in neutral.
Wind up the windows and listen.
If you hear a roll/roll/roll noise.
Then your front race has flat spots.

These occur in the opinion of Bearing Service Company when cars are left idle for several years in storeage and the oil evaporates out of the bearing races and condensation and diurnal breathing causes internal moisture build up and corrosion.

It happens in aircraft engines outdoors all the time.
The only solution is to inhibit the parts as per manufacturers specs.
Fill them full of clean oil.
My gearbox was idle from 1984-1992 and from 1995-2005.
I am surprised there is only one bearing noisy.


As my geology teacher said, Everything in nature tends to disorder.

[river]

Hi,

The suck it and see test is..
Start your engine, let it idle and let the clutch out in neutral.
Wind up the windows and listen.
If you hear a roll/roll/roll noise.
Then your front race has flat spots.

Which is what my box has been doing for quite some time now.

.. roll.. roll.. roll...

seeyuzz
river

[Vios-GT_07]

River should give u rep for this.. very interesting read

good luck with it mate hope it all works out

[RT104GT]

Hi,



Which is what my box has been doing for quite some time now.

.. roll.. roll.. roll...

seeyuzz
river

On further investigation.

The front counter shaft bearing is spring loaded, there is an extensive pictoral detail of how you assemble and reassemble it.

The question is, what does the spring loading do?

part of the ratchet feel is due to this loading.

So it may not be bearings.
I am waiting to pull the bearing off the main shaft to see.

P51 series 5 speed made under licence to Porsche 1973-1979.



Bearings in use in P51

Top row Left Nachi 52/28 C4 Thrust 53/38 ZN NSK centre and input shaft main bearings.
Counter shaft left KOYO RMS7 Centre NSK NUF22/28 Right end Nachi 5205RXZN

At the extreme right hand end of the lower counter shaft is a spring loaded gear set. U can see ^^ the 2 rows of teeth.
This gear passes all the energy for every gear except 4th.
The outer gear is 1mm thick and heavily sprung loaded.

According tp page 3-119 of the Celica P51 gearbox disassembly pages.
This part is called the Counter Gear Plate and Springs.
It is known as a backlash (SCISSOR GEAR) for anti rattle.
Correctly setup it is offset and springloaded by half a tooth.





Front cluster and bearing. Brake bands and needle roller set.

[RT104GT]

River should give u rep for this.. very interesting read

good luck with it mate hope it all works out

I used a "Fanny Collar" which is two half moon shoes that clamp around the bearing and I pressed it out.


New countershaft bearing and scissor gear installed.

This is my rebuilt P51 counter shaft with correct setting for scissor gear, new scissor gear and new bearing, looks great .

[RT104GT]

BEARING IDENTIFICATION ON WIERD BOXES.

MAIN FRONT AND CENTRE:

MAKE NSK PART NUMBER 6332ZN
(SHIELD ON ONE SIDE SNAP RING GROOVE ON OUTER RIM)




Bearing Numbers

Bearing numbers are alphanumeric combinations that indicate the bearing type, boundary dimensions, dimensional and running accuracies, internal clearance, and other related specifications. They consist of basic numbers and supplementary symbols.


CENTRE COUNTER SHAFT

MKE NSK PART NUMBER NU F 22 28




http://www.tec.nsk.com/




Bearings should not be unpacked until immediately before mounting.
When using ordinary grease lubrication, the grease should be packed in the bearings without first cleaning them. Even in the case of ordinary oil lubrication, cleaning the bearings is not necessary.

The lubricating oils used for rolling bearings are usually highly refined mineral or synthetic oils that have a high oil film strength and superior oxidation and corrosion resistance. When selecting a lubricating oil, the viscosity at the operating conditions is important. If the viscosity is too low, a proper oil film is not formed and abnormal wear and seizure may occur. On the other hand, if the viscosity is too high, excessive viscous resistance may cause heating or large power loss. In general, low viscosity oils should be used at high speed; however, the viscosity should increase with increasing bearing load and size.

SO ??? VBX80 or higher?? lower?? LSD OIL ATU Oil??

[RT104GT]

Bearings for older gearboxes getting pretty hard to source however a step by step explanation helps..heaps

http://www.gizmology.net/bearings.htm


KOYO RMS7
(Counter shaft rear trust bearing)
non metric in a meteric gearbox
In stock Aussie.
ID (22.225) x OD( 57.150) x WIDTH( 17.462)



identified. see above.

NACHI 5205 RXZN 6205ZNR

NACHI 52/28 C4 62/28 NR C3

Drew a blank from the following......

Dynaroll Technical Info.
Basic Bearing Info from Motion Bearings.
The Bearing Reference Center by Machine Design.
SKF Online Bearing Calculator
Formulation of Bearing Numbers from NSK Automotive, Australia.
Bearing ABC's from NSK Automotive, Australia.

[RT104GT]

Gasket kit and bearings have arrived.




Awaiting on one centre bearing.

GASKET KIT ex W50 fits OK $110.00.





Bearings ex PK hamilton $119.00




MAIN INPUT and CENTRE MAIN: Counter rear: Counter Front: Rear Main shaft/extn.


Next step removing and refitting bearings.


P51 reassembly:



New front main bearing





All tolerances in spec between 0.015mm and 0.020mm clearances.