I have a 9 bolt with 0578029 011 BW BE 3-70 A

It has a hand written 4G 238 in yellow

Does anyone know the gear ratio?

Thanks in advance!

 

There are some 9-bolt codes at the bottom of the list below, but whether yours is there or not I can't say offhand. Frankly, the best/surest ID is to pop the diff cover and look for the number stamped on the ring and pinion--or count the teeth. For example 40 on the ring, 13 on the pinion. Divide 40 by 13 = 3.08

It's impossible to determine when the fluid was last changed and filled, so you'd be killing two birds with one stone.

http://sethirdgen.org/reardata.htm

JamesC

 

Thanks James,

Those numbers were stamped on the ring and did come from inside (no tag outside, I had it off a couple of years back to change fluid and cover gasket.) and yes it was also had written in yellow, so I think it's aftermarket but didn't count the teeth.

Weird none of the numbers inside match the numbers listed in the link.

Could I not tell by jacking up ride and counting drive shaft revolutions to wheel revolutions?

 

Sure (but because I'm **** in such matters, doubt wiggles in).

JamesC

 

I haven't been able to get to car due to work, but I did find the pics.
Any idea?

 

Since you already have it apart, count the teeth... the ONLY reliable method, other than finding the tooth count stamped on the edge of the ring (which it appears it is not).

It at least looks 3 series to me. See https://www.thirdgen.org/forums/tran...up-3-73-a.html for a great pic of a 2 series.

 

Thanks, these pics were taken a couple of years ago. Long since back together. You would think these numbers would be crossed referenced to ratio via manufacture?

 

Well then take the cover back off and count the teeth.

I gave up "thinking" stuff like that A LONG TIME AGO (probably about the time your daddy was getting close to being a gleam in your grandma's eye), and instead started just LOOKING AT THE PARTS I wanted to know about. Much easier that way and less hassle & confusion altogether. No chance for mistakes or ambiguity. Go straight to the fact at hand and bypass all the intermediaries.

In the time you've spent typing on the Internet about "thinking", you could already have gone out and LOOKED, and you'd already have your answer.

 

I'm happy to hear you think I'm so young.

About 5 years ago I had to take that plate off 4 times in a row due to a axle bearing going and issues with a replacement bearing (make: F.A.G). Needless to say, I don't recommend F.A.G. products (lasted less than 1000 miles each time) and do not want to ever take that plate off again! Besides why waste perfectly good oil with less than 12K on it. With any possibility of oil getting dirty (not sure how you could drain without this) I wouldn't use it again simply because I had so much issue with the bearing replacement.
With the oil, LS modifier and gasket, it cost close to $100 in parts here in Canada and that was over 5 years ago.
I can't believe that the manufacture can't confirm their product stamp numbers to the gear ratio. I will contact them directly and let you know what I find out.

 

I haven't confirmed this 100% yet, but 9 bolt.com offers gear sets and sell a 3.70

Mine is stamped 3.70, but it through me, due to the ratio, I would have thought it to be a 3.73 to match other ratios available in the 10 bolt.
I will see what else I can find, but am certain ratio is 3.70

 

Sure you can & it is a 100% reliable way to do so. You'd have to be a complete moron to mess up counting the revolutions in such low numbers.

 

3.70 is correct for a 9-bolt. The ratio between the 9- and 10-bolt are slightly different: 3.23/3.27 and 3.42/3.44, etc.. The link below may be helpful in the long run:

https://www.thirdgen.org/forums/faq-...now-about.html

JamesC

 

You would accomplish that by going to the quarter car wash first, and stopping along the way to pick up a can or 2 of engine degreaser; and blast the hell out of the scene of the crime. Then you could even use a funnel and a coffee filter to guarantee to remove any grit that accidentally fell in.

I'm continually amazed at how people think this stuff is so "hard" to do that they'll take the risk of all the uncertainties in the "count the turns" type of guessing methods, with SO MUCH money on the line in buying parts. I'll freely admit I'm far from the brightest bulb on the string, and that some of you smart people out there maybe have stuff totally mastered that I'm so stupid I haven't even noticed exists yet let alone learned about; but that one just completely has me stumped. It's just not that "hard".

There actually IS (or at least, has been) a 3.73 gear set available for the 9-bolt, but the ratio in that range that GM used, and the more common replacement one as well, is indeed 3.70. The only cars I know of that it came in were the 85-up L69 TransAms. The ratios in the 9-bolt generally have overall fewer teeth than the equivalent 10-bolt ones; so 3.70 is 10 & 37 whereas 3.73 is 11 & 41, 3.45 is 11 & 38 while 3.42 is 12 & 41, and so on.

 

Thanks to everyone for your input!

With the stamp and knowing that ratio was offered, I'm convinced it is a 3-70. My hwy revs always seemed high for a 355

I thought about cleaning it, and with filtering the oil you should be 100%, but after replacing 3 B9 axle bearings in a row, and with the added cost of $100 bucks, I wouldn't tear it apart again just to retrieve info - my T56 swap hasn't been cheap and I can't be throwing away that kind of money.

I only wanted to know for the swap, to ensure I could use 6th gear. I've read that with low stock gears you can't.

With gas what it is, I can't wait to cut my highway revs in half (should be close to 1550 RPM, before I was over 3000) should also see added city fuel economy and not to mention the the fun/performance to go with the six speed.

Why give that money to gas companies? When I can give it to myself for my enjoyment.