rear ends

deliver · Post by **deliver** » Tue Feb 21, 2006 9:36 pm

Ok I have talked with Mike Young today who has talked me out of replacing my 4 speed with a 5 speed. What he said makes sense to me now. He suggested changing my 3.9 gear in the rear end to a 3.7 gear from a 2000 car. He said the rear ends were a truck rear end. My question is does anyone know what rear ends third member are interchangable with my present rear end. Thanks.

Post by **23yrRebuild** » Tue Feb 21, 2006 11:10 pm

I believe the early ones came with the 3.89 .

mikew · Post by **mikew** » Wed Feb 22, 2006 12:33 am

Interesting suggestion....

All else being equal, the 3.7 rear end will get you a slightly higher top speed at the expense of slightly slower acceleration.

Is this what you want?

Usually, those chasing 'performance' will go the other way - for example using a 4.11:1 rear end. Racers might use a 3.7 on long open tracks where top speed is important, but a 4.x or even 5.x where the track is short and tight and acceleration is important.

The roadster rear end is a H190 which is also used by a number of other Datsun/Nissan vehicles, but the axle size, and the number of splines, is unique to the roadster. Try a search for 'H190' in these forums.

Mike

spyder · Post by **spyder** » Wed Feb 22, 2006 3:08 am

What are you trying to accomplish? Speed or economy. A numerically higher pumpkin with more gears might do both.

67 1/2 1600 · Post by **67 1/2 1600** » Wed Feb 22, 2006 3:13 am

I put in a 3.7 in my car and I did notice a difference. But the difference went away when I installed 185/60s on my car... compared to the bigger tires that were on there, now it feels like I have the 3.9 in again.

deliver · Post by **deliver** » Wed Feb 22, 2006 8:26 am

Well my understanding when replacing a 4 speed with a 5 speed behind a 1600 you run into a torque problem in lower gears. You can over come this by stroking the 1600. What I am looking for is being able to run down the highway at 80MPH with out twisting the engine so hard. Don't care about hurting my neck on take off. I have gone to 15 inch wheels and believe the taller gear 3.7 will also help at 80MPH. Also the cost and work in doing a 5 speed swap could be avoided.

Datzoom · Post by **Datzoom** » Wed Feb 22, 2006 9:38 am

I am running a 3.5 rear end in one of my 2000's. My other 2000 is on the opposite side of the spectrum with a 4.38. Each serves it purpose very well. The 3.5 car is my driver / highway cruiser. The 4.38 car is used for auto-x, etc.

The real benifit of the taller gears is not increased top speed but lowered rpm's. 80 mph in 5th while turning 3200 rpm , now that's cruising.

Datzoom

Cruiser
Buzzer

deliver · Post by **deliver** » Wed Feb 22, 2006 11:10 am

datzoom what did you get the 3.5 gear out of?