To five speed or not.

[oldbugr]

As a new 2002 owner, I can find a fair amount of debate on keeping the four-speed or switching out to a 5 speed. Looking at the price to do all this seems to make this a fairly expensive conversion.  

Where I get lost in the weeds is that the 4 speed and the 5 speed both wind up at a 1.0 final ratio. But the 5 speed seems to prefer a lower rear gear around the 3.91 as a popular choice.

 

With the lower gear in the rear, it sure doesn't seem like I am getting a lot of bang for my dollar.

 

So what am I missing on either side? It looks to be a 4 to 5 grand all in with me doing it with the reared. 

 

Another concern is having to beat the knot out of a perfect bottom to make room for the slave. 

 

It appears to have been debated a ton on this site but I wonder how the people that have done the switch and the advantage they experienced. 

 

[Henning]

There are mainly two types of 5-speeds:

- a sports version with 1st gear left rear and final ratio 1.0. Called dogleg. 02-era parts with Porrsch synchro (delicate) and slave on the bottom at the front, E21-series era parts with Borg Warner synchro slave at the side. Better sprint but no rpm or noise reduction. Both ex-tre-me-ly expensive and not absolutely a daily driver's thing.

- an overdrive version with standard H-scheme and 5th added right forward. Ratio of 5th about 0.8:1. None in the 02 era, only 3-series. Always Borg Warner (more reliable) and slave at the side. Lower noise, less thirst, good for highways. Good parts situation, prices clearly lower than for doglegs.

 

henn

[SydneyTii]

I have one, over 15 years old now, yes it’s a great mod.
In terms of cost not sure I’d pay to do the e21 5 speed over drive,  prices are higher now, that said the non mechanical speedo boxes are cheaper I believe and GPS speedos are a. nice and reliable thing now so that’s a good path.

In terms of driving comfort yes it’s a real bonus on the freeway, there are a couple of different rears ends to mate to so maybe think what you want from the car and choose one that suits.

In terms of repairing the e21 box, bearings are the biggest issue but I believe there is some engineering that can be done to overcome that issue, one of the Aussie guys is looking at this right now but I think metric mechanic stateside does the same.

hth

 

[tech71]

I installed a Getrag 240 into Survivor, my 76 2002 with the 3.91:1 rear differential bout 5 years ago.

Its great especially driving on the freeway/ highway.

Cost way, way less than  4 grand back then  but prices have climbed.

The 240 is slightly narrower than a 245 so fits the tunnel a bit better (no rubber mallet massage required) 

Main drawback with the. 240 is most have no drive to run a speedometer cable, a GPS speedometer must be installed. Several options to go with there from a simple HUD GPS for around $30 to a Speed hut unit fitted into your instrument panel.

 

Edited May 19 by tech71

[NickVyse]

When they were €500 for the box, prop shortening and your own work it was a no-brainer. If you have to add a zero to that figure I'd be very happy keeping a 4. Tell yourself the 4 speed box is lighter and is the Colin Chapman choice.

[zinz]

Where the OD box shines is long, open highway trips. (Multi state adventures to MidAmerica, or The Vintage…) Hours at 75mph in a 4 speed can feel like a lifetime. If all you do is short trips and your highway time is 55-65 mph.. keep the 4 speed. 

The 3.91 diff? If you live where the roads are twisty the lower final drive makes the 2002 come alive. By far, the best fun-factor modification I’ve done. You don’t have to have the expensive LSD to accomplish this either. An open 3.90 from the later cars works just fine for 1/3 the cost, or less. (If my memory is correct, the later, automatic cars had that 3.90 diff)  Annnnd…it’s a direct bolt-in swap.

 

Ed Z

[dlacey]

BMW produced this model for ~10years and both gearbox options were direct top gear... Yes, it's a little buzzy up at 90mph, but when you put your foot down the car accelerates smartly... The technology for an OD 5th existed, but BMW never implemented  on the 02.... 

So, unless you spend the majority of your time on the freeway it would be better to invest in tires & brakes to make the car more fun on back lanes & city streets.

[jimk]

In hindsight, for US roads and street driving, I would change the diff ratio to 3.45:1.  It's so is so much less costly and would get about the same freeway, long distance cruse as the $$ OD trans these days.  There is a lot more to installing a OD trans than changing the gear ratio.

['76mintgrün'02]

A 3.45 behind your engine might be fine, buy I appreciate the grunt of a higher ratio with mine.

 

My '76 has a 3.90 differential (California cars got the 3.64) and the original four speed transmission.  Last year, I drove 3k miles round trip on I-90 twice; two days each way, with the tachometer pointing straight up.  The speedometer is 10% optimistic, so this is what 80 mph looks like.

 

That was in 90 degree eastern Washington weather, which was the only time I saw the temp needle above horizontal.  It dropped back down if I kept the rpms closer to 4k.

 

When I look back at those photos, it looks like fun.  I drove 950 miles one day and would have gone 50 more if the alternator hadn't crapped out.  Maybe I'll achieve a 1,000 mile day next time. 

 

It seems like most of the noise (in my car) comes from wind; not the engine or transmission.  Something happens between 3900-4100 rpm that seems to make my engine happier, based on how it sounds.  It may have to do with how the exhaust (stock, aside from the Tii manifold) resonates, but it seems to like running above 4k.

 

I made those trips solo though and it would take a durable co-pilot to tolerate the din. 

 

I suspect I'll make that drive again this year (visiting my mother) and may install the 3.64 I have in storage before I go.  It'll be interesting to see if I want to swap the 3.90 back in when I get home.  I'll bet I do, because most of my driving is on back roads and I appreciate the extra pep.

 

Tom

[tech71]

There are still occasionally some deals to be had that make the bottom line somewhat less painful.

Like this one for So Cal folks:

 

[visionaut]

I love my 5-speed OD, but I use it different. I rev it like the 4-speed and just go faster! Always satisfying to wind up 4th, shifting into 5th at 100. 😊

[bergie33]

I had a tii with a 4.11 rear end mated to the 245 5 speed.  That was fun.

 

The easiest and cheapest way to get a 5 speed and 3.90 rear end is to find a 320i that someone is getting rid of.  Even better if it's a 320iS.  I bought my 320iS for $3,000 3 years ago.  When I discovered the rust was more than I thought, I kept the 5 speed, 3.90 LSD and Recaro seats for myself and parted out the rest of the car.  Came out about $4,000 ahead.

[oldbugr]

7 hours ago, zinz said:

Where the OD box shines is long, open highway trips. (Multi state adventures to MidAmerica, or The Vintage…) Hours at 75mph in a 4 speed can feel like a lifetime. If all you do is short trips and your highway time is 55-65 mph.. keep the 4 speed. 

The 3.91 diff? If you live where the roads are twisty the lower final drive makes the 2002 come alive. By far, the best fun-factor modification I’ve done. You don’t have to have the expensive LSD to accomplish this either. An open 3.90 from the later cars works just fine for 1/3 the cost, or less. (If my memory is correct, the later, automatic cars had that 3.90 diff)  Annnnd…it’s a direct bolt-in swap.

 

Ed Z

I should have added I live at 5000 ft here in Reno. Your open idea makes good sense. 

[oldbugr]

6 hours ago, jimk said:

In hindsight, for US roads and street driving, I would change the diff ratio to 3.45:1.  It's so is so much less costly and would get about the same freeway, long distance cruse as the $$ OD trans these days.  There is a lot more to installing a OD trans than changing the gear ratio.

 

5 hours ago, '76mintgrün'02 said:

A 3.45 behind your engine might be fine, buy I appreciate the grunt of a higher ratio with mine.

 

My '76 has a 3.90 differential (California cars got the 3.64) and the original four speed transmission.  Last year, I drove 3k miles round trip on I-90 twice; two days each way, with the tachometer pointing straight up.  The speedometer is 10% optimistic, so this is what 80 mph looks like.

 

That was in 90 degree eastern Washington weather, which was the only time I saw the temp needle above horizontal.  It dropped back down if I kept the rpms closer to 4k.

 

When I look back at those photos, it looks like fun.  I drove 950 miles one day and would have gone 50 more if the alternator hadn't crapped out.  Maybe I'll achieve a 1,000 mile day next time. 

 

It seems like most of the noise (in my car) comes from wind; not the engine or transmission.  Something happens between 3900-4100 rpm that seems to make my engine happier, based on how it sounds.  It may have to do with how the exhaust (stock, aside from the Tii manifold) resonates, but it seems to like running above 4k.

 

I made those trips solo though and it would take a durable co-pilot to tolerate the din. 

 

I suspect I'll make that drive again this year (visiting my mother) and may install the 3.64 I have in storage before I go.  It'll be interesting to see if I want to swap the 3.90 back in when I get home.  I'll bet I do, because most of my driving is on back roads and I appreciate the extra pep.

 

Tom

I guess I'm not used to winging a motor that hard. Seems like 4 grand in anything causes a lot of extra wear. What do you think redline is on your motor?

[oldbugr]

32 minutes ago, bergie33 said:

I had a tii with a 4.11 rear end mated to the 245 5 speed.  That was fun.

 

The easiest and cheapest way to get a 5 speed and 3.90 rear end is to find a 320i that someone is getting rid of.  Even better if it's a 320iS.  I bought my 320iS for $3,000 3 years ago.  When I discovered the rust was more than I thought, I kept the 5 speed, 3.90 LSD and Recaro seats for myself and parted out the rest of the car.  Came out about $4,000 ahead.

That was smart.