Wanted early 203 diff in good condition

Wilko

New member
Mine is an early 1951 with a narrower housing. I have a 403 diff complete that looks ok but I don’t have the spring mountings . Has anyone got a parts breakdown which shows that detail? Also, can the whole 403 assy be fitted to my early 203? I have measured the track and it is the same.
 

GRAHAM WALLIS

Member
1000+ Posts
You need the late 203 axle tubes. Early 403s have springs and shocker mounts in the wrong place. Late 403s are different again and have shocker mounts for telescopic.
 
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GRAHAM WALLIS

Member
1000+ Posts
Also, from 1960 403s had fine spline axles, these will fit the 203 axle tubes. Plus from 1961 the 403 diff ratio was 4.2 not 5.7 so very tall gearing with the overdrive 203 gearbox.
 

Wilko

New member
Mine is an early 1951 with a narrower housing. I have a 403 diff complete that looks ok but I don’t have the spring mountings . Has anyone got a parts breakdown which shows that detail? Also, can the whole 403 assy be fitted to my early 203? I have measured the track and it is the same.
So the axle tubes that I need have the spring mounts cast integral with the tubes and not a bolt on option.
 

GRAHAM WALLIS

Member
1000+ Posts
So the axle tubes that I need have the spring mounts cast integral with the tubes and not a bolt on option.
Yes, your 403 diff has spring mounts as part of the fabricated sheet steel trailing arms? The later 403 has cast in mounts but on top of the tubes, not slightly ahead of them.
 

Restorer

New member
Trevor , as Graham says - late 403 diff has fine spline axles ( better but not absolutely essential ) and has different diff ratio , so that if you go that way - change to a later gear box - if that is possible!( Graham will have a better idea as to later gear box into 1951 203 - different gear box mounting!) You need to check whether the 403 diff you have is fine spline or early - if an early - diff ratio is ok but no fine spline. Then you will need axle tubes from a late 203 - they bolt onto the 403 diff centre. You can fit fine spline axles to the early 403 diff if you change the drive gear in the diff centre - last if using the fine spline axle in the later 203 axle tube - you need to change the seal in the outer part of the axle tube about 6 inches in from the end - a fairly easy drive in/out with a suitable length of pipe.
wilko
 

Wilko

New member
So the axle tubes that I need have the spring mounts cast integral with the tubes and not a bolt on option.

Also, from 1960 403s had fine spline axles, these will fit the 203 axle tubes. Plus from 1961 the 403 diff ratio was 4.2 not 5.7 so very tall gearing with the overdrive 203 gearbox.
Yes, your 403 diff has spring mounts as part of the fabricated sheet steel trailing arms? The later 403 has cast in mounts but on top of the tubes, not slightly ahead of them.
Yes, your 403 diff has spring mounts as part of the fabricated sheet steel trailing arms? The later 403 has cast in mounts but on top of the tubes, not slightly ahead of them.
Hi Graham thanks for your help - yes you are correct re the mounting. I got this diff from Basil Moran in Casterton and the worm wheel looks in good condition compared to mine which although has plenty of tooth depth, has scuffing , pitting and is noisy which could be bearings. I don't want to take the diff out without a game plan that might leave the car unusable for a lengthy time as it is fully registered and I want to have fun! The 403 diff looks like a 1955 vintage if that the photo shows-am I right?
IMG_1620.JPG
IMG_E1629.JPG
IMG_1620.JPG
 

Wilko

New member
Trevor , as Graham says - late 403 diff has fine spline axles ( better but not absolutely essential ) and has different diff ratio , so that if you go that way - change to a later gear box - if that is possible!( Graham will have a better idea as to later gear box into 1951 203 - different gear box mounting!) You need to check whether the 403 diff you have is fine spline or early - if an early - diff ratio is ok but no fine spline. Then you will need axle tubes from a late 203 - they bolt onto the 403 diff centre. You can fit fine spline axles to the early 403 diff if you change the drive gear in the diff centre - last if using the fine spline axle in the later 203 axle tube - you need to change the seal in the outer part of the axle tube about 6 inches in from the end - a fairly easy drive in/out with a suitable length of pipe.
wilko
Thanks for your help - I think the later C2 gearbox wont fit a 1951 model as the floor pan is too small unless you take to it with a ballpein hammer! If this 403 diff is a 1955 model then I would just need the later axle tubes then.
 

Wilko

New member
Semaphores? Did you establish from the pics of the diff I included that it is a 1955 version with the right ratio?
 

Russell Hall

Member
1000+ Posts
No, I know his stock of cars. He had a green early model with semaphores. There was another early model I gave him and a 1959 still with lever arms. If the oil filler is the large 203 type it will be an early model with suitable ratios.
 

Wilko

New member
No, I know his stock of cars. He had a green early model with semaphores. There was another early model I gave him and a 1959 still with lever arms. If the oil filler is the large 203 type it will be an early model with suitable ratios.
Mm I took this diff out of a wreck he had tipped up on its side. It was a pale green but didn’t have a look at the motor. The 55 markings on the diff housing don’t necessarily mean that it is a 55 model?
 

Wilko

New member
Mm I took this diff out of a wreck he had tipped up on its side. It was a pale green but didn’t have a look at the motor. The 55 markings on the diff housing don’t necessarily mean that it is a 55 model?
Not sure what you mean about semaphores.
 

Russell Hall

Member
1000+ Posts
Side blinker arms. The 1955 and early 56 403's had them. Sounds like the car that was a 1956 reg so 1955 on the diff would be consistent. That car has sat there for thirty years but that shouldn't make any difference to a diff.
 

Wilko

New member
That’s my worm-wheel and also the wreck that I took the diff from. You can see the torque tube swinging in the breeze.
 
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