JBrady

Some of you remember I had a 96 LS400 prior to trading on my 99. The 99 is more powerful at 290hp/300tq vs the 96 at 260hp/270tq. BUT... with the difference in gearing points, 99 has a 5 speed and 3.27 final vs the 96 had 4 speed and 3.62 final, makes the cars behave differently.

The 96 had a GREAT punch at 70mph. It would downshift and the tach would jump to 5000rpm and it would scoot Above 75mph the car would not downshift and the "snap" wasn't there.

The 99 is LESS responsive at 70 but MUCH more responsive at 80mph.

Overall the 99 is faster but that "snap" or quickness is not that dramatic. So, while answering a post on LSDs it finally came to me... duh... the 96 had the 3.62 gearing!!! The difference is a touch over 10%. Torque (unlike power) can and is multiplied by our gears. The 96 had 270lb/ft and 3.62s vs the 99 with 300lb/ft and 3.27s.

Here is what happens at the torque peak between each car.

96, 270 x 3.62 = 977.4 lbs of torque
99, 300 x 3.27 = 981.0 lbs of torque :eek:

Virually identical. This explains the feeling or snap between the 2 cars as being VERY similar. Now, the power difference means that the torque curve is both higher and wider meaning that overall there is more force from the 99 even vs. the 2nd gens gearing advantage. A LOT MORE... but, instantaneous response is still close.

Now, my next goal is to install a set of the 3.62s in my 99 and I will have:
300 x 3.62 = 1086 lbs of torque... Yeah BABY!!!

healerhand

John,

Do u know what is the final gear for the 1st generation LS? Would the higher (taller) gear fit into the 1st gen?

whitels

Great write-up. Have you checked into the GS3/4 rear end gearing ratio? Wouldn't it also fit the LS? But I guess, the 3.62 from the 96 should be a good compromise and a start.

JBrady

Whitels,

The GS400 has the same 3.27s that the 98+ LS has. I do not know about the GS300 although it probably has 3.77s or so. Curiously, in reviewing the Supra manual it states that the differential on the non-turbos has 3 mounts vs. 4 mounts on the turbos. The n-turbos have the 3.77s vs 3.27/3.13 (year dependent) of the turbos. So, I am guessing the GS uses the 3 mount arangement as the people doing this swap say it is a bolt in.

Now, the SC people have ran BOTH types so I will need to check with Clint or someone with hands on regarding this swap.

For myself, I think I have located a differential from a second gen LS400 with the 3.62s. This should be a bolt in. I did a couple brake stands earlier and it doesn't look like the speedo goes up as only a function of tranny speed. I will double check this but would be very good news as the gearing change may not effect the speedo or odo (one of my concerns).

This will allow me to swap the entire carrier and not worry about setting up the finicky hypoid gear lash and pattern. Once this is done I hope to try the Powertrax positraction product soon to be available for these carriers.