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Urgent 7in and 7.5 In diff interchangability.
carnut - 30/1/06 at 03:32 PM

I have a 3.62 xr4x4 7 inch diff and a 3.9 7.5" diff.

I was going to take the open diff oput of the 7.5" and put it in the 7" keeping the ratios in their respective casings. However when I took the back off the 7.5" diff, I noticed the crownwheel was a lot thicker. Does this mean that I can't swap the open diff for the LSD thats in the 7" diff? Or is it just the crownweel and pinion that have to be used in the 7.5" case and everything else (ie output shafts and the actual diff) are interchangable?

Thanks
Carnut

stevebubs - 30/1/06 at 03:40 PM

As I understand it (from a 3rd hand armchair point of view), you should be fine in what you want to do, but would defer to an expert...

[Edited on 30/1/06 by stevebubs]

JB - 30/1/06 at 03:48 PM

I am sure I looked at doing this but something is different, cant quite remember what but would be please to hear if some one says otherwise.

John

Liam - 30/1/06 at 03:53 PM

I doubt that 7" internals are the same as 7.5" ones. But I dont know for sure and it has never been confirmed on here. Only real way to find out would be to take your diffs apart . My question is why do you want to do this? You certainly dont need the strength of a 7.5" diff unless you're building a 400bhp heavy monster. If your goal is a 3.92 LSD then just get a 7" one from a 2 litre 4x4 and flog your 3.62 - should break even.

Liam

carnut - 30/1/06 at 03:59 PM

My goal is to use the open diff bits to make a spool with 3.62 ratio in the 7" casing with lobro type driveshaft fixing.

[Edited on 30/1/06 by carnut]

[Edited on 30/1/06 by carnut]

James - 30/1/06 at 04:00 PM

quote:
Originally posted by Liam
I doubt that 7" internals are the same as 7.5" ones. But I dont know for sure and it has never been confirmed on here. Only real way to find out would be to take your diffs apart . My question is why do you want to do this? You certainly dont need the strength of a 7.5" diff unless you're building a 400bhp heavy monster. If your goal is a 3.92 LSD then just get a 7" one from a 2 litre 4x4 and flog your 3.62 - should break even.

Liam


Seconded!

carnut - 30/1/06 at 04:02 PM

See above post

Liam - 30/1/06 at 04:26 PM

Wouldn't an open 7" 3.62 set you back about 50p and be hanging around in piles at every breaker? Even if you only find a push-in shaft one, get any other lobro open diff for another 50p and shove the flanges in. Actually your 7.5" lobro flanges may fit into a push-in diff even.

Liam

[Edited on 30/1/06 by Liam]

stevebubs - 30/1/06 at 05:02 PM

quote:
Originally posted by Liam
Wouldn't an open 7" 3.62 set you back about 50p and be hanging around in piles at every breaker? Even if you only find a push-in shaft one, get any other lobro open diff for another 50p and shove the flanges in. Actually your 7.5" lobro flanges may fit into a push-in diff even.

Liam

[Edited on 30/1/06 by Liam]


sounds like a better plan...

James - 30/1/06 at 06:00 PM

quote:
Originally posted by carnut
See above post


Sorry mate. You beat me to it by 1 minute!

Cheers,
James

NS Dev - 31/1/06 at 09:17 AM

yea.....wot Liam said!

Incidentally, for a given diff, a lower ratio (higher number) the crownwheel will be thicker as it still has to engage with the pinion, which will be smaller. Look at a Ford Atlas 5.1:1 diff for a classic example!

carnut - 1/2/06 at 11:16 AM

For everyones info.
The internals for the 7" and 7.5" are NOT interchangable. This includes CW&P, Diff, Output flanges. I pulled it apart yesterday.

NS Dev,
The crownwheel wasnt just a little thicker, its more like double the thickness.