Kyle86

iTrader: (1)

I don't own a press, but wanted to swap out my 3.73s for 3.08s for a few reasons. I wanted to share so others could see it can be done in an afternoon, on jackstands, used gears, and without a press. I did doublecheck my backlash with a cheapy dial indicator, but it is not needed if your paint pattern is correct.

Emptied the housing.



Old ring gear off, new ring gear on



Popped old bearing off using blocks of wood and a brass hammer, and a big harbor freight bearing separator.





Cut the cage off the old bearing to press new bearing in on.



Used c-clamps and wood to press new bearing on



Gear paint shows the wear mark. I had to swap the shims around to get it to line up right. I got lucky and the pinion shim was practically dead on!



I could tell the backlash was close by wiggling the carrier and how the wear pattern looked, but I had a dial indicator so figured checking wouldn't hurt.



Gear swap was a success. Gears do not whine, and cruises nicely at 3000 rpm at 75mph. Turbo like the new gear a lot too!

oil pan 4

iTrader: (1)

I want to swap the gears and put a posi in my suburban's 10-bolt rear, this is just what I have been looking for, thanks.
My twin turbos should like the lower engine revvs.

Kyle86

iTrader: (1)

Welcome!! You will never want to go back to low gears ever again!

oil pan 4

iTrader: (1)

Actually its a 3.42 to 3.08 swap.

big gear head

"I did doublecheck my backlash with a cheapy dial indicator, but it is not needed if your paint pattern is correct."


I don't agree with this. Backlash should always be checed with a dial indicator, even if it is just a cheap one. Backlash mostly controlls heel to toe movement of the pattern, and is very limited. A big change in backlash will only show a very small change in the pattern, so the backlash could be way off and not show on the pattern.

Kyle86

iTrader: (1)

My apology for the misinformation if that's true. It's worked out for me that way twice though. Both times I checked with a dial indicator though. Good catch Big gear head.

oil pan 4

iTrader: (1)

What is an ideal back lash setting for a used gear swap?

big gear head

The best way to do it is to measure the backlash before removing the gears from the original housing. If you can't do that then it's a shot in the dark. Most of the time I go toward the large side. Most gears are set between .007 and .009 when new, so I go for around .009 to .012 on most used gears.

Used gears should be et up by the pattern on the coast side. Get the pattern as good as you can and make backlash adjustments by what the pattern says. Most of the time backlash adjustments don't make much of a difference, but sometimes it can be the difference between a good enough pattern and a great pattern.

Kyle86

iTrader: (1)

My backlash is .005. I tightened in the ring gear till the pattern looked correct. I figure the paint takes up a couple thousanths anyway. The pattern is what I look at and I just make sure there is some backlash at several points on the ring gear.

big gear head

I think that's too tight. Even when they were new they would have been at least .007, so even if they were new with no wear on them at all that would be too tight. Figure at least .001 to .002 for wear and that would put them at .008 at the very least.

Kyle86

iTrader: (1)

I think it works just fine. The first rear I built was also .005 and it ran for 50,000 miles with no problems. It was also used gears and handled many 1.7 and 1.8 60' track launches. This one has about 1,000 hard street miles on it and also 5 track passes in the mid 11s. Neither rear whine or make any noise. I had a very accomplished transmission builder walk me through the first one. I know you're a smart guy; thanks for your input.