Hi everyone - first large post here. And boy what a complex thing these ratio's can be!! Just a little starter. I built the below car over 6 years and finished it in summer of 2010. It's a millimetre perfect re-creation of the 1970 A2 Gunston Capri. Hope you like it? Anyhoo, I have been running the M75 axle with 2.92 CWP ration and LSD - and whilst it's OK - we all agree the axle ratio is too tall for optimum running. If I was getting 30mpg I'd keep it at 2.92, but as I'm not I may as well get some good performance!! My axle is an M75 with 2.92 crown wheel and pinion. (38 teeth and 13 teeth respectively). I do not know what's stamped on the gears themselves. LSD fitted after these pics taken. Now I'm told that if I want to change the ratio's in the M75 I can only get the following gears to fit the M75 -3.08 ,3.73 , 3.89 & 4.11 - (I've been informed that I could possibly get 3.23 gears for the M75 but they would new brand new and cost about 800 dollars). But if I had the M78 axle I could have these gears: 3.23, 3.27, 3.45 & 3.89. Now to the all important questions:- (bear in mind my axle has been custom narrowed and I have custom Moser shafts from USA, and I really don't want to change the rear axle) My intention being to get somewhere around a 3.23 - 3.45 ratio in the M75 case. 1. Is the above info re. the ratios for the M75 accurate? 2. Is it possible to put the M78 gear set in the M75 case albeit with some machining? Not a problem for me. My shafts are 25 spline. 3. Do the bearing sets ( Set 309 and set 67) work with the M75 gear and the M78 gears? (wondering what if any the main differences are between the M75 gear and the M78 gears? 4. will my LSD still fit if I chnage the gears? I appreciate this is a heck of a thread for a first posting, but I've been stumped on this in the UK as no-one seems to have a clue about such axles. Hoping someone can chuck some ideas my way. thanks Chris ps feel free to add any thoughts and suggestions to the ratios I have considered. My transmission is Tremec T5z with the following ratio's: 1st 2.950 2nd 1.940 3rd 1.340 4th 1.000 (5th) 0.730 __________________ "At 20 your heart rules your head, at 40 your head rules your heart - at 60 your bladder rules everything!"

We have Borg Warner diffs in a few Aussie cars. We have mainly 'BW78' but they actually have 7.5" CWP's, available in 2.92 up to 4.11. Some Fords have 7.8" CWP's apparently. 25 (2 pinion) and 28 (4 pinion) splined axles. A VK Commodore EFI possibly has a Borgwarner 3.23 or there are thousands of 3.45 ratios about from a VL Commodore! I have a 28 spline centre in a 25 spline housing (will interchange) and a CWP from a 25 spline car!

These are the marks on my CW gear:- So, based on that what do you reckon on the correct gears to make mine a 3.23 or 3.45 ratio? 1. Does the EB stamp mean my gears are from a 97 EB Ford? 2. My side gears are still 25 spline - so will the replacement crown wheel still bolt to the carrier? I have 3/8th bolts holding the CW on. 3. Will the pinion drive be the same dimensions as my 2.92 pinion? I am concerned about the bearing set that I will need . Currently I have set 67 and set 309 bearings. thanks for the help so far.

if you want a 3.45 then you just buy a crownwheel and pinion from a VL Commodore. http://www.ebay.com.au/itm/GENUINE-B...em 2ebb80af7e (http://www.ebay.com.au/itm/GENUINE-BORG-WARNER-0575-SERIES-3-45-DIFF-GEAR-SET-V8-/200714268542?pt=AU_Car_Parts_Accessories&hash=item2ebb80af7e) It will bolt on to your centre and wont affect your side gears. There are a few different size bearings but the OD is still the same so will fit on your diff hopefully, unless its some weird model diff!

Quote: Originally Posted by vhr32 [View Post] if you want a 3.45 then you just buy a crownwheel and pinion from a VL Commodore. http://www.ebay.com.au/itm/GENUINE-B...em 2ebb80af7e (http://www.ebay.com.au/itm/GENUINE-BORG-WARNER-0575-SERIES-3-45-DIFF-GEAR-SET-V8-/200714268542?pt=AU_Car_Parts_Accessories&hash=item2ebb80af7e) It will bolt on to your centre and wont affect your side gears. There are a few different size bearings but the OD is still the same so will fit on your diff hopefully, unless its some weird model diff! thanks - just wondering if might know if that crown wheel has the 3/8ths bolt holes? Someone said the 3.45 CW has 7/16ths? But what do I know...............

No Idea. I had a 3.45 CWP but I chucked it out!

Quote: Originally Posted by vhr32 [View Post] No Idea. I had a 3.45 CWP but I chucked it out! I've decided to bite the bullet and get a 3.45 AND a 3.23 - see what fits see what works see what I like and machine anything that does fit!!!