D60 4.55 to 4.10?

[etg]

Hey all, it's 1/2 price weekend at pick your part and I found a D60 open with 4.1 gears. I have an open D60 with 4.56 gears, turned by a new 700r4 powerd by a sbc 350 block (kinda). I was wondering what kind of recommendations you all had for lowering the gear ratio. As you've all figured out I'm wound out really fast on the freeway, and don't want to tire my newly built block out too quickly. Therefore I have a few questions, any and all answers are much appreciated.

1. Is a 4.1 downgrade good enough with a 700r4 to keep my rpms down?

2. What kind of RPMs should I expect at 70 mph running 26 inch tires at 4.10 and 4.56 (no tach, and haven't really run my truck yet)?

3. Is changing down to 4.10 as simple as pulling em out and puttin the different ones in, assuming the same shims will keep it all aligned?

I'd like to go back and buy these tomorrow, I don't think the ring and pinion will be more than 50 bucks total. I've also read that to go below 4.10 I'd have to replace the carrier, and I'm trying to stick to the low buck method for now.

[68chevyfuelie]

As an opinion, 4.10 or 3.73's would be a good choice with a 700 tranny. If you go too high a gearing, like 3.42's/3.08s, the tranny in OD actually lugs the motor below it's useable torque range, wasting more gas. There are lots of gear ratio/rpm charts on the net, you can plug all the info in and it'll spit out your rpms.

Changing ring and pinion and carrier is pretty involved, but you should be able to reuse all your old shims and get pretty close. The hardest part is pulling the bearings off the pinion/carrier without the proper tools. The are shims in behind the carrier bearing to set backlash.

Yes, you will need a new 3 series carrier, for 4.10 and down gears. I have one in the shop I will send you free, if you would send me your 4.56 carrier/gears. I might even have a posi carrier if that would help the trade.

[69 longhorn]

Tire size makes a diff on overall gearing also. The 26" tire is pretty short(I ran 29" tires with 4.10s in my longhorn). If you like the tire size,& do not plan on changing that, I might suggest a 3.54 gear for your D60....it should work out well with the OD & the tire height. As a rule, I like to figure on a 28" tire....& 3.73 is as good as it gets(best of both worlds). good acceleration, & good cruise rpms with OD. I am currently running a 3.42 gear/29" tire, & .76 OD.....my old truck will cruise 105 @ 3150 on the tach. 1st gear is still deep enough (3.28 on the Richmond), to get the 4200 lb truck gone pretty quick....but it ran like a "RAPPED APE" with 4.10 gears! Just give a little thought to what you want ....freeway flyer, or 1/4 mile at a time. There are also some good calculators, to figure gearing/ tire size & rpms that you intend to run. best of luck,crazyAl

[etg]

I am guessing on the tire size, I plan on running 20's with lo profile tires in the future, but now have 16's and standard? size wheels. Would it be worth it to regear twice, one set now and one later when I get the right wheels?

Also, when on the freeway I was gassing it to keep up to speed, and when I put it in neutral it coasts smoother/faster longer than when in drive. It's almost as though the engine brakes the truck when in gear at higher speeds, is this due to the 4.56 gearing?

[raycow]

Why not buy the complete 4.10 rear? For whatever extra it may cost, this is a much safer route than trying to swap the gears into your present housing, where there are all kinds of interesting ways for things to go sour.

Ray