Is 4.10 too much gear for auto m30b34?

[motohunter4]

Is 4.10 too much gear for auto m30b34?

[XAlt]

4.27 was used on the final Big Six E32s.

Doesn't sound too bad.

[Hit Man X]

4.27 was used on the final Big Six E32s.

Doesn't sound too bad.

EXACTLY what I have been telling people for years.

Stock E23 gearing is pathetic and all done for fuel economy, I guess...but when the vehicle is so lugged down with a few passengers, the A/C running, fan clutch locked, and your foot is buried in the throttle, you do not really return stellar economy.

[motohunter4]

The same basic transmission too. I almost went for 3.73, but I want a 4.10 for some reason.

[Hit Man X]

If you have the 3.25:1 diff in your car, provided it is a 10:1, you would see a decent difference with a 3.73:1... if you have the 8:1 euro car, you will go from a 3.46:1. Not worth the trouble to me for the swap to just do a 3.73:1

Go for the 4.10:1 and do not look back.

[XAlt]

I'd be verbally abusing a car with a 2.93 LSD\3.15 paired to an M30.


There was a very good reason they kept increasing the ratio.

[motohunter4]

I'd never leave 2nd gear.

[GazM3]

I had a 4.10 in a e28 auto low comp. it finally felt like it had 3.5ltr. Cruising rpm was high.

Ive heard on good authority that the e23 uses a taller first gear than the other 4 spd autos. Even with my 3.73 diff I still get over 50mph out of first. Perhaps look into the auto from the e28 or e24.

[motohunter4]

I'm at 2000 rpm at 70mph. Theoretically I would be around 2400 with 4.10 which I can live with.

[Hit Man X]

I turn 2700rpm @ 70mph with the 3.91:1 in my 10/84 with a 225/50R16 tire.

Your 4HP22 has a 0.72:1 overdrive ratio.

[motohunter4]

So you think it's more like 3?

[Hit Man X]

So you think it's more like 3?

Three what?

[motohunter4]

3000rpm? I figured with a 3.46 I'm looking at a 18.5 percent increase in rpm's going to a 4.10?

[Hit Man X]

3.91:1 to a 4.10:1 gains right around 100rpm increase, nothing to write home about. You have an 8:1 euro car? Neat, I thought I was the only person that ever had one of those.

Regarding ratios, all BMW 4HP22 and 24 have the 2.48:1/1.48:1/1:1 ratios for the first three gears that I have ever come across. I believe the wide ratio 4HP22s were in Volvos. BUT the Volvo units have reduced clutches throughout most of the gear train, makes me wonder if the hardparts are weaker accordingly. Besides, close ratios keeps you in the powerband better on the upshifts.

I have heard some early 3HP22s had wider ratios. My 12/82 745i's 3HP22 had the same ratios as the previously stated 4HP22/24. ATSG states the 3HP22 is an updated 3HP20 with different ratios which is an update of the 3HP12.

My experience is based on transmissions I have built. My HP22/24 hybrid has exactly the same ratios.

[motohunter4]

I guess I have the low compression one. 59 ecm and 3.46 gears with cats and o2. My build sheet was super short. A/C power windows (green thermal) and clear coat delete. Before anyone knocks it I'm rocking the original paint ant it ain't bad.

[motohunter4]

I have a large case diff. I can swap a medium e30 one right? Will the covers swap?

[Hit Man X]

Yes on cover swap. I tossed in a 3.91:1 med case into my old 735i. I have it for sale if that is any interest to you.

Does the last seven of your VIN go similar to - 1XXXXXX?

[motohunter4]

0810xxx. I love the 80's

[motohunter4]

Well 4.10 is probably the best mod I've done other than the suspension. A lot better around town. I'm turning 3000 rpm at 80 mph. We'll see about fuel economy.

[Hit Man X]

Now you can accelerate and be in vacuum. It drastically transforms these cars.

I had city economy go up with off boost and with the old 735i. Lost a bit on the freeway. I recall a guy named Evan from the bimmerboard days, he averaged 1.5mpg loss (combined) going from a 3.25:1 to a 3.73:1 in his 733i as I recall. Nothing to fuss about at all, considering how much better the car drives. It is no M30+T, but totally different.

[motohunter4]

Here's the old large case 3.45
20170606_170622.jpg

And the medium case 4.10
20170609_154321.jpg
The flanges will not swap over and E30 ones are too small for cv axles. You also can't use the large case cover if you want a drain plug.
20170606_172143.jpg
20170606_204534.jpg20170609_164254.jpg

[motohunter4]

Then you have these left over after sourcing the correct flanges, 2 bolts and appropriate cover
20170612_182015.jpg

[Jay535is]

I think the link is in my signature, but I've put together a transmission/diff spreadsheet and calculator that takes all the guesswork out of this.