Mopar 7.25 rear axle rebuild

[Getawaydriver]

Hello
Does anyone know where I can get my 7.25" Chrysler/Dodge rear axle rebuilt?
Does anyone specialise in these old axles.
The axle is attached to my 1974 South African Dodge SE, so may have been built in Australia or South Africa or may indeed be American.

[Dave999]

if its is original it will be a SA built Borg Warner M78 maybe M75 but probably M78

no drain plug

octagonal/ round back cover with 9 bolts
tag on the left upper bolt looking at the back
it will say borg warner or have the BW zig zag logo under the snout that the pinion sticks out of


see also BTR and Spicer Axle Australia all the same company just a list of owners all made M78 with subtle differences

gonna be 7.8 inch ring and pinion
or maybe 7.5 if its a borg warner M75

MMMmmm ....ROBUST.... they are compared to their size


same axle used in fords and holdens and skylines and toyotas in Aus
used in Camaro IROC and firebird TA 82-92 in US

if you provide the parts geoff hauser can rebuild it no probs
some parts shared with ford and gm axles in respect to shims spacers etc

he did mine

its a reasonably bog standard, "take the centre out through a hole in the back", style axle. will provide little challenge to anyone who builds axles

if you undertake it yourself its like a dana i.e a PITA to do compared with say an 8 3/4 mopar

all adjustment is done with shims and spacers
and you need a case spreader or a heavy mate with a good sense of balance

I got a 2.92 open centre if you need one or just the gears
got some 3.23 gears as well may be for a 75 not a 78. no issue they fit
got some 3.9 but they'd be hard work

or if you just want another open axle to swap your brakes onto got one of them as well 2.92:1 open centre, i don't need 3, one can be yours

for my rebuild
i got a GM 9 bolt rebuild kit off RATECH in the states
got some wheel bearings and seals from oz
got a new centre
got new axles
sent it to Geof
collected it a week later

if its a mopar 7 1/4 i'd put a borg warner in
if its a mopar 8 1/4 you have no issues....

if you want to build up an LSD M78 i have some bits i will sell and can also point you to suppliers in OZ to make those bits work with your 25 spline axles.


Need a photo
what size is your engine if its 360 you might have 2.77:1 ratio gears and a 4 spider gear LSD which means it can only ever use 2.77:1 ratio gears. other than that it is the best of the 25 spline axle M78s, and an ideal source of parts to make a 4 spider gear m78 for a charger with 3.5:1 ratio gears


dave

[Blue]

Southern axles at Watford should be able to help, plenty of American axle experience.

[Getawaydriver]

Thanks Dave and Blue,

I thought the axle might be a Chrysler 7.25" because of the shape of the diff cover, it has 2.5" axle tubes and roughly measures 55" between the back of the flanges. It doesn't have a drain plug, but the only numbers I can find are cast onto the underside of the pinion housing (snout). The numbers are:-
P448
1624
HB8

Dave I would be interested in buying an axle from you, although the thought of ordering the wrong parts for a rebuild scares me a bit. If you have a good usable rear axle that doesn't whine that would be great.

I've attached some photos, hopefully you can identify the axle. I would normally tackle a rebuild job like this myself but because of my uncertainty of ordering the wrong parts and I don't have an axle case spreader I'd rather leave the job of rebuilding a rear axle to a professional who can order all the correct parts.
The engine is a Chrysler 383 big block. Originally I think the car had a straight six engine in it, so if the rear axle is original it maybe under rated for the current big block engine.

Kind Regards,
Phil.

[Dave999]

well all but mid 60s aussie cars had a splined pinion and yoke rather than that flanged arrangement

it looks like a borgwarner in many respects, however the lack of borgwarner logos, the weld plug holes (big) for the axle tubes and the rear cover with the drain plug certainly point to it being a mopar 7 1/4

I have an Aussie M78 bare axle

what you get is a 2.92:1 open diff to the brake back plates and the yoke on the pinion. its a small dodge size, used internal circlip thingys like 318 dodge trucks up into the 90s. no yoke straps, 1 thing i don't have spares of, however you may find the flange you have fits BUT swapping may well screw up the preload on the pinion bearings
its a nice red rusty colour so needs a clean up
i can take the back off and have a look...post up photos etc

it has not turned a wheel in 15+ years so i can't say if the axle seals are going to be ok

you would need to add
vent
brake pipes
full aussie brakes...
and you might need to do something with the prop shaft to convert from the flanged one you have

i reckon its worth £80 not becasue i know of anything wrong with it more to do with the fact that you are the only interested customer in 10 years

Now they used these behind 360s but not 383s

they have the same saddle to saddle centre distance as a mid 60s B body as near as damn it 44" pre 71 valaints were 43 1/4 your will be 44 3/8

there is part of me that says get a mopar 8 1/4 in there or indeed a 8 3/4 and never have to worry again. the issue will be finding one at reasonable cost and you'd still have to get a prop that fits

both of those will cost more than £80 + the 200 or so you will need to spend on brakes i'd guess

here is some Borg warner diff stuff from aussie Street machine mag

https://www.streetmachine.com.au/featur ... -tech-talk


Dave

[Getawaydriver]

Thanks Dave,
If you could post some photos that would be great.
Regards
Phil.

[Dave999]

i'll pull it out sometime this week

Dave

[Dave999]

probably going to be the weekend

traffic, rain, and kids going to clubs after school have stolen my time so far

weekend has little planned so parts mining is a distinct possibility

i'll see if i have any brake parts as well.

dave

[Dave999]

axle pics

apologies

if 2 axles in pic its the one on the top. the other is out of my car

Dave

[Dave999]

also available

i have a sure grip centre in 28 spline. would need 25 spline gears and cones added
open centre with good 2.92:1 gears
a set of 3.23:1 gears 7.5 inch not 7.8 will fit
a set of 3.89:1 gears in 7.5 inch not 7.8 will fit

the gears are more suited to a VF or VG diff they had M75 sized gears but they fit an M78 housing the morgan aero 8 uses this configuration

spare axle shafts

Dave

[Getawaydriver]

Hi Dave,
Thanks for the pictures and sorry I haven't replied until now, but I've been in France.
I'm going to take the diff cover off my car this week to have a look inside to try and assess the extent of wear.
I'll also attempt to remove the flange type prop coupling to measure the diameter and count the splines of the pinion shaft. From this information I can make a judgement on what to do for the best. Thanks for your help and patience.
Regards,
Phil.

[Dave999]

not a problem its been there for 10 years..its not going anywhere

I'm working in greece back at the weekend so i too, am away....

Dave