14 replies to this topic

[Pairaminis]

I'm quite near to the start of a rebuild on the 998 in my 1984 sedan and had a question about the best gearbox to mate it with.  I have the 3.1 that came in the car and I also have a 3.44 from a 1275 motor I was given.   Which of these gearboxes would be the best for a 998 city car (the 1275 motor is shot)  that will rarely spend any time at 55 mph?  I understand that the 3.44 would have better acceleration than the 3.1 but the 3.44 would provide lower revs at highway speeds. Is this true?  Also can I use either box without modifications?

Thanks.

Jack

[Stiggytoo]

I would say that the 3.44 diff is your best option. Better acceleration. Again, with a 3.44 diff, comfortable cruising speed (bearable) is around 60-70mph.   

[Spitz]

I used a 3.1 in my PUP with a 998.  It was fantastic.  It's not a big enough drop from the 3.44 I had to make a massive difference.

 

It was still great around town and the acceleration was fine.

 

I also took the truck on a 2800km round trip which saw me climbing through the Rocky Mountains as well as the flat prairies.  Sure, it was a little harder to maintain speed on the climbs but not terrible.  with 10" wheels it pulls about 3300rpm at 100 ( 62mph )

 

I would fit a 3.1 in my Woody that has a 998 if I had one to fit.

[timmy850]

The diff is reasonably easy to swap from one gearbox to another if one is in better condition than the other. Whether either gearbox will fit depends on what gearboxes you have and what 998 you have.

My 998 has the original 3.76 diff, which means it gets off the line pretty well and is normally pretty close to the power band. At 60mph you are doing 4000rpm, but that's fine, it'll do that for hours.

[Cooperman]

3.44:1 is ideal for a 998 which will rev more freely than a 1275. At 65 mph a 3.44:1 will be using 4000 rpm and a 998 will cruise at well over 4000 rpm all day long with no problems.

In fact, a 3.76:1 is good for a 998 and is what the original 998 Cooper had as standard.

[lawrie124]

I had a 344 in my van and it was a nightmare on motorway cruising.

Stick a 31 in and you will be able to trundle along at 80mph or more, where legal.

Just done over 1000 miles across Europe. Wouldn't dare on a 344

..... But what do I know?

[timmy850]

I had a 344 in my van and it was a nightmare on motorway cruising.

Stick a 31 in and you will be able to trundle along at 80mph or more, where legal.

Just done over 1000 miles across Europe. Wouldn't dare on a 344

..... But what do I know?

The original post specifies he won't be doing over 55mph. Speed limits are lower in the US and Australia than in Europe with your fancy motorways 

 

The top speed limit in the state I live is 110kph (68mph) and the majority of highways are 100kph (62mph)

[Swift_General]

3.44 for me. Personal choice really but from what you say you're using your car for I think you will enjoy it more with that final drive.

[Stiggytoo]

I had a 344 in my van and it was a nightmare on motorway cruising.

Stick a 31 in and you will be able to trundle along at 80mph or more, where legal.

Just done over 1000 miles across Europe. Wouldn't dare on a 344

..... But what do I know?

Just did 1300 miles across Europe and the 3.44 sufficed

[lawrie124]

ok; if OP is saying 55mph max then 344 or 36 is good.

[Midas Mk1]

3.2 is a good compromise between the two :)

[Spitz]

 

 

The original post specifies he won't be doing over 55mph. Speed limits are lower in the US and Australia than in Europe with your fancy motorways 

 

The top speed limit in the state I live is 110kph (68mph) and the majority of highways are 100kph (62mph)

 

 

Not so....speeds on US ffreeways are high.  Not sure what the speed limit is, but traffic flow is usually 120 - 130  (75-80mph).  You go much slower and you'll be run off the road...lol

[Ethel]

3.4 is what the factory fitted when all they were bothered about was the best matched gear ratios.

You could always put in earplugs, more carpet or taller tyres if you occasionally hit the freeways.

[Pairaminis]

Thanks so much for all you comments.  They are very helpful.

 

While the Interstate Highways in the USA generally have 65-70 mph speed limits, the roads outside my small town are all 55 mph and I will only occasionally be using them - and will probably never venture on an Interstate.  So, based on most of the comments here I'm leaning toward the 3.44 FD.  My 998 is an A+ with the 3.1 I mentioned. The 3.44 I have came from a 1979 Clubman which is pre A+.  Will the 3.44 fit the A+ okay, with no major changes, if I decide to go that way?

Jack

[carbon]

Your 3.44 crownwheel and pinion will be a straight swap for the 3.1 in your A+ box.

 

If the outputs are same type (ie both with pot joints) and in good condition then just change over the whole diff assembly,

 

Main point to watch is keep the crownwheel and pinions as matched pairs, don't mix them up.