Rear Gear Change

[vms4evr]

Well I finally decided and all the parts are ordered and on the way to the shop. I'm having an outfit down in Charlotte do the gear swap. They have a good reputation and Vette, Camaro, Firebird with LTx and LSx is all they do.
I have the factory 2.59 gears in the Dana 36 w/auto trans. I decided to go with Strange 3.54 thick gear set. They've setup a few already and like them better than the Richmond Gears.
So I'll be offline until Tuesday night. I'll let you all know what I think of them after I get back home.
Now the hard part. 500mi break-in with no serious stuff...:eyerole
Wish me luck. Hope everything goes smooth.
Graham

 

[JT ZR-Won]

Great news Graham........let us know how you like them

Jay

 

[vms4evr]

Ok I got a few minutes to make an update. This is a little long, sorry. Looks like I'll be through the 500 mile breakin in no time cause I got another 300 mile road trip to do...

First off. The outfit that did the job is MorePerformance Inc. They did a great job and are great to work with. Their website is their company name. Check it out. They do serious LTx and LSx work. Vette, Camaro and Firebird. They have some awesome engine packages and buildups they do. They're in Charlotte, NC.

I went with Strange instead of Richmond for the gear set. I chose 3.54 over 3.73 because I'm on the highway a fair bit and 3.54 works out as a really good compromise. If you're mainly an intown driver then going with the 3.73 would work. They like the results they are getting with Strange gears and prefer not to use Richmond because of compaints of excessive gear whinning.

Getting the gears setup took some time. The Dana 36 is harder to work with than the Dana 44. No crush sleeve and the Series-2 carrier that the original 2.59 gears came in is tight to work in. He had a fair bit of time invested into getting the shimms just right so all the gear lashes came out the way he wanted. The end result is a really good fit, no slop. Also used the Master install kit which contains all the bearings and seals. Most definetely worth the extra $50-$75 to do them all while you have it torn down.

He did the work for a flat rate and swears he'll never do another Dana 36 gear swap for what he charged me. I don't blame him. He spent a good 4 hours just setting up the gears. I'd say in total it was about 10-12hrs. I left it over night.

The Strange Gear (US Gear) is the thick type because it is replacing the 2.59. The Gear Set cost about $365. Master Install kit cost about $120. Speedo gears and sensor is about $50. I ended up paying about $850 all done and out the door.

Now for the driveability. Well I'm under breakin so I have to behave. Even at low RPMs I can tell you that it makes a big difference from 2.59 to 3.54. I can now use Overdrive intown and it accelerates nicely even in OD. In Drive it climbs to 3,000 RPM very quickly and accelerates very crisp. Once we get the breakin done we'll do some full throttle tests :J

We had a minor oops with the speedo gears so we have to replace them. Not a big deal. Just annoying.

I'll post some more info later for anyone who is considering a swap. I have all the part numbers etc...

Graham

 

[JT ZR-Won]

Cool Man
That is a big difference going from 2.59 to 3.54. In my old vette, I went from 2.73 to 3.75. The differnce was unreal.......

Wait till you chirp 2nd gear after your break in period
Thanks for the update Graham.....

Jay

 

[rg lane]

rear end swap

hi....

i have a 1990 6 speed with a 3.30. i am very interested in your final results....i am considering app. 4.09 ratio...should make a considerable difference. thanks for your info.

rg lane

 

[Topless]

yikes!
I can get the ASR light to come on when I shift to 4th in my 92 6spd. I have factory 3.42 (or 3.45?). The idea of 4.10s is a little slippery.

 

[vms4evr]

rg,
The 90 has an L98 which as I understand has great low end torque and playing with the gears should match up to the power curve of your engine. The biggest recommendation I see for an LT1 w/6sp is 4.11. Super low 1st and good cruise in 6th. So I'm not sure you want to bump it that high. I get the impression with that engine you want to stay 3.45-3.75 range.

topless,
yeah in my92 auto a lot of guys told me to go up to 3.73 but to watch out as it would change the driving habits. one of the guys who has gone to 3.73 in his 92/auto said with ASR off if he punches it to jump out to the passing lane the car will come right around! and it took him a few weeks to stop chirping the tires every time he turned a corner at gave it the gas... his only other mod is a cat-back exhaust, open-air K&N.

with the 3.54 gears in my auto 1st gear in Drive now goes away very quickly and it's a firm bump when it shifts to 2nd. then 2nd pulls hard. i like it next week i should be through breakin. we're gonna check a few things at the shop then do some full throttle tests... can't wait...

graham

 

[rg lane]

rear end ratio 90 6 speed

thanks for info....i am leaning toward a 3.75-3.85 ratio...i calculated the various speeds,gears & rpms and this seems to be what i am looking for.

 

[Topless]

Graham, I know what you are talking about. I had to adjust my driving habits when I got the vette. In my mustang, I used to drop to 3rd, punch it, and pass. I did that in the vette, and it got a little tail happy. I have learned not to drop the clutch when turning. :s

-Mike

 

[vms4evr]

Ok time for another update covering the speedo gears part this time. Hopefully by Friday I'll have some comments about full throttle testing

Converting a 92 auto, 700R4, from 2.59 to 3.54 gears requires all 3 parts in the speedometer gears to be changed. The 2 gears, both drive and driven. Also the speed sensor because the original gears were 2.59 the sensor is for a 2-Series. Now I put in 3.54 gears so I need a sensor for a 3-Series.

10456089 - Speed Sensor (3-series)
8642620 - Drive gear, 15-tooth (grey)
25513050 - Driven gear, 43-tooth (purple)

If you were to look up these parts you would find that the sensor actually fits auto and 6sp with 3.x rear gears in 92. Now the 2 gears actually are listed for an 89 with 6sp. Because the 89 6sp had a 3.54 rear axle. Exactly the gear ratio I chose.

So the speed should calibrate properly and the gears will mate properly. This matching is important. If you don't get the right pair not only will your speedo be off but you may chew up one of the speedo gears. Don't ask me how I know :eek

In order to put the speedo gears in you will have to remove the tailshaft from the transmission. The drive gear lives in the tail housing. The driven gear and sensor go in the side hole on the transmission. If you only had to do them then the tail doesn't need to come off.

Graham

 

[vms4evr]

Ok. Small update. The parts I listed above for the speedo are all in now. We did an oops keeping the orignal sensor. Now the matched one is in. Works fine. Turns out they are a perfect match for the 3.54 gears. My spreadsheet and the car agree. So the speedomter must be darn close. I've been told to expect up to a +/- of 3mph trying to retrofit cars with gear changes.

Part of the whining noise I heard came from the sensor being broken and it's shafting spinning around aimlessly... The plastic gears didn't get hurt at all. There is still a distinct whine from the gears but it is not objectionable at all. It's running smooth.

Before in OD, 2000rpm=78mph. Now it's 62mph. So on the highway you'll need to give it a little more gas. About 2500rpm. I still averaged 25mpg on the way home doing all interstate driving.
In town I can now use OD! and only need D for fun :s

 

[vms4evr]

Well I thought I'd post a final update to this thread. I got my 500 mile break-in done and behaved myself. Then as soon as I get through that it rains for 3 days. Go figure...

Today was clear and cool. Roads dried out. Soooo, ya know what that means. Testing time

I'm still experimenting with the proper takeoff approach. Just flooring it is impressive but you get too much wheel spin. But it's kinda fun with the a$$ end swayin about while it jumps up into 2nd. A few launches with the tach around 2000rpm holding the brakes down with the left foot seems to work well. The difference in acceleration is significantly improved! The LT1 is well into its power band in no time. The car literaly jumps into 2nd gear and barks the tires. You were right Jay. It barks on 2nd :cool

All in all I'm impressed and would recommend this approach to anyone who wants better acceleration over the 2.59 gears :J

BTW, Gas mileage hasn't suffered much either. Well except for today...

Graham

 

[Topless]

Excelent!!

MIke

 

[wulf]

accelöeration measurements - not only the feeling ...

Hi vms4evr

You say your car literaly jumps into 2nd gear and barks the tires and that it barks on 2nd ...

Have you really measured the 0-60 mph acceleration? Of course it certainly feels more powerfull with the shorter axle ratio. However, I ask myself whether the mesured values really improve by this since you may nedd two gear changes to 60 mph
if the auto trans switches at 55 or so ... Also if you take the 1/4 mile times do they really improve?

I am thinking of changing my gear ratio from 2.59 to something ...
So what is your top speed and at waht rpm do you achieve it? Did you ever try to find that out?

wulf

 

[vms4evr]

wulf,
yeah, leave it in D, turn off the ASR, and pucnh it! a$$ end lights up and it grabs pretty quick, then when it shifts into 2nd the car jumps forward. 1st on the 700R4 trans is pretty low. changing the gears just increases that affect.
no i haven't put it on a strip and timed it 0-60 or 1/4 mile. 0-60 is quicker with the 3.54. i don;t have the time but there is no doubt in my mind. it makes 60 in 2nd gear.
With 25.7in tires and 3.54 gears, assuming the auto does a ratio of 1.0 in D and 0.7 in OD.
In D 115mph @ 5322rpm. In OD 165mph @ 5346rpm.
That's the calculation. I'm not going to be testing the top speed. Been there done that.
If you want to consistently cruise the autoban at 100mph + then you might as well stick with your 2.59 gears. You could go to the 3.07 but I doubt you'll notice it that much. When I cruise the Interstate at 75mph in OD now I'm @ 2500rpm.
Go to the software tools area on this website or anyone that sells gears and use the gear calcualtor. You plot out any gear change and what to expect in mph/rpms.
Graham