So I'm looking at getting a truck with 3.42s in the rear, and I have a dana 60 with 3.54s. I did the calculator thing and it comes up as roughly +/-1%. Are these too far off? It's been a long time since I messed with gears, and really don't feel like swapping gears out if I don't have to.....
CK5
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Dumb gear question
- Thread starter b454rat
- Start date
I am assuming the 60 is front. What type of wheeling do you plan to do? What size tires? Those gears are real high for much over a 33.
You will be under driving the front. In loose dirt or sand, no big deal. Pavement you would notice the scuffing in tire wear.
You will be under driving the front. In loose dirt or sand, no big deal. Pavement you would notice the scuffing in tire wear.
For the most part you will barely notice it. Unless you do lots of driving on pavement with it in 4wd
It's an 88 1 ton, new body style. It has a Dana 70 3HD with GU6 3.42s. I have a 78/79 HP60 that has the 3.54s. Truck has 315/75s on it and plan on staying with that size. Truck also has a 454 auto, and wheeling will be very mild. Mostly be trails and mud, where the gears will come in handy for extra wheel speed. But mainly wanted to stay with this gear is for highway use. G/F and I have two 4 wheelers, and plan on doing some riding on trails hours away. I've had trucks with 4.10s and 35s, and not terrible, but not great. My old 89 that I SAS'd had a 454 auto, and I drove it all the time with 3.73s and 36s, 38s, and at the end 40" boggers and went fine down the road. I do have a divorced 203 that I might use for a doubler, if I need more gear.
And on a side note, I rarely use 4wd. Also never use it on pavement. Only time I do is in mud or snow off road. I may swap the rear out for another 70, if I can find one with 3.55s and a posi would be nice. Gonna start looking at Ferd and Dodge vans for one....
And on a side note, I rarely use 4wd. Also never use it on pavement. Only time I do is in mud or snow off road. I may swap the rear out for another 70, if I can find one with 3.55s and a posi would be nice. Gonna start looking at Ferd and Dodge vans for one....
I had a '71 K5 I sold to a guy that had a 3.08 rear axle and a 3.73 front axle,someone swapped in the rear and used any ratio they could get,just to get the truck driveable again...I did not discover this till after I had it several months,and went to use 4WD one snowy morning,and the truck didn't want to move,it bound up,and the front hubs would release with a loud bang,and the truck would lurch...
I found a 3.73 axle eventually,but never got around to swapping it in,I had two other 4x4s to drive,so it was low on my priority list...gave it to the new owner,he never did install it either--someone told him he could get away with using larger tires up front to help make up for the ratio mismatch,he tried that and it worked well enough for it to be driven on snow or dirt OK,but it would have been better if he had installed the right axle in the rear..
Seeing your gears are not that far off,maybe the tire size option would work for you ...
I found a 3.73 axle eventually,but never got around to swapping it in,I had two other 4x4s to drive,so it was low on my priority list...gave it to the new owner,he never did install it either--someone told him he could get away with using larger tires up front to help make up for the ratio mismatch,he tried that and it worked well enough for it to be driven on snow or dirt OK,but it would have been better if he had installed the right axle in the rear..
Seeing your gears are not that far off,maybe the tire size option would work for you ...
I guess only time will tell. I have to wait to see if the guy is gonna buy my 87. If he don't then it might take some time to get the truck. But I know that my G/F is friggin awesome, she said that if I don't have enough that she could help 
Once I get it stupid B/L has to come off, then rebuild the front 60, either make or buy the SAS mounts, steering, shocks, etc. etc.
Once I get it stupid B/L has to come off, then rebuild the front 60, either make or buy the SAS mounts, steering, shocks, etc. etc.
Stomis
Professional Amateur
You'll have no issue there. Theres way more room in spline engagement play in pinions, driveshafts, gear/chain lash in rears and tcases etc.
Yota guys run a toy rear with 5.29s and dana 44 front with 5.38s ALL the time.
Yota guys run a toy rear with 5.29s and dana 44 front with 5.38s ALL the time.
In one of my old Chiltons manuals,it states the front axles on GM's are not an "exact" match,as an example they claim a truck with a 4.11 rear axle ratio actually has a 4.09 ratio front axle,they stated because of the different size in ring gears they couldn't make a 100% exact match...how true that is I dont know,I'm just repeating what I read...
I'd think there has to be some leeway,when tires are often different diameters by up to 2" even ones marked the same sizes,in different brands..
I found a chart online that shows the tire diameters from brand to brand and the tire models,and it shows how much difference in MPH the tires spin at,when they are off only a slight amount...
I looked up a 265/75-16 Wrangler's diameter VS a General 245/75-16 I'm using for a spare,and the General tire is almost 1.5" smaller diamter,and the difference it spins at is almost 2 mph,so now I can see why the truck feels a bit weird going down the road,and why my hubs will violently disengage if I lock them and try driving over 20 mph,even with some snow on the roads..spider gears must be working overtime!...I'm hoping to find a mate to the other 3 tires ASAP..
I'd think there has to be some leeway,when tires are often different diameters by up to 2" even ones marked the same sizes,in different brands..
I found a chart online that shows the tire diameters from brand to brand and the tire models,and it shows how much difference in MPH the tires spin at,when they are off only a slight amount...
I looked up a 265/75-16 Wrangler's diameter VS a General 245/75-16 I'm using for a spare,and the General tire is almost 1.5" smaller diamter,and the difference it spins at is almost 2 mph,so now I can see why the truck feels a bit weird going down the road,and why my hubs will violently disengage if I lock them and try driving over 20 mph,even with some snow on the roads..spider gears must be working overtime!...I'm hoping to find a mate to the other 3 tires ASAP..
The way I always understood it was the 4.11 rear 4.09 front (I know they exist because I found a 70 something K20 with that setup) was for the full time 4WD models so the front, being slightly higher geared, would spin the front drive shaft slightly slower thus keeping constant even pressure on the transfer case and not letting the front end run slack gears all the time while the rear axle does all the work. But that could be way off in left field, I didn't design it. It may have had to do with the front tires wearing faster or even turning radius reduction.
Otherwise you can do the different size tire thing and carry 2 spares.
If you choose that route, use this calculator to figure out which sizes will work together.
http://www.grimmjeeper.com/gears.html
Hypothetical
If you are running a Turbo 350 tranny and 35" tires here are the differences.
3.42 on the left / 3.54 on the right. Driving in a straight line in 4WD with traction the faster pulling front would be trying to drag the rear a bit.
Then again you can have more than a 1 MPH difference running new tires vs worn out tires.
If you are running a Turbo 350 tranny and 35" tires here are the differences.
3.42 on the left / 3.54 on the right. Driving in a straight line in 4WD with traction the faster pulling front would be trying to drag the rear a bit.
Then again you can have more than a 1 MPH difference running new tires vs worn out tires.
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Carcinogen
1/2 ton status
Wouldn't the front trying to pull be better than the rear trying to push the slower moving axle? In terms of offroad performance?
The slight difference between front and rear gears from the factory over the years is simply from the design restrictions between the different sized axles in the front and rear. There was no intentional design parameters so one end or the other would pull slightly faster.
The difference between 4.09 and 4.11 is a whopping 0.49%. That is equivalent to the difference between a 34.8" and 35" tire....which you could easily see just by a small difference in wear, tire pressure, or weight between the front and rear tires.
Back to the OP, you should not have any issues between the 3.42 and 3.54 gears.
The difference between 4.09 and 4.11 is a whopping 0.49%. That is equivalent to the difference between a 34.8" and 35" tire....which you could easily see just by a small difference in wear, tire pressure, or weight between the front and rear tires.
Back to the OP, you should not have any issues between the 3.42 and 3.54 gears.
Stomis
Professional Amateur
That's gotta be in your head that you could feel that...
Never said I could feel it. It was just the way the old military and early CJs were setup.
My '60 model CJ5 was that way.
I saw an article many years later in one of the truck magazines that said that some company, Toyota I think, had designed their trucks with a slightly faster gear in front than back to prevent the system from bucking back and forth.
The truck mag waxed effusive about the brilliant designers who fixed problems that American designers had not even recognized yet.
Yeah, right. That was in the '70s, and Willys had done that in the 40's.
That was the same mag that a few years later informed all its readers that every shop manual and owner's manual ever written for Jeeps had a misprint.
And that the closed knuckles on the front axle were supposed to have cup grease in them instead of 90 gear lube.
Never mind that the top kingpin bearing was splash lubed, or that there was a fill line, and seals to keep the oil in.
They stated that you could not keep 90 weight oil in there. I wrote them a letter informing them that mine had 90 weight in them, and they did not leak.
Shortly thereafter I quit reading that mag.......
My '60 model CJ5 was that way.
I saw an article many years later in one of the truck magazines that said that some company, Toyota I think, had designed their trucks with a slightly faster gear in front than back to prevent the system from bucking back and forth.
The truck mag waxed effusive about the brilliant designers who fixed problems that American designers had not even recognized yet.
Yeah, right. That was in the '70s, and Willys had done that in the 40's.
That was the same mag that a few years later informed all its readers that every shop manual and owner's manual ever written for Jeeps had a misprint.
And that the closed knuckles on the front axle were supposed to have cup grease in them instead of 90 gear lube.
Never mind that the top kingpin bearing was splash lubed, or that there was a fill line, and seals to keep the oil in.
They stated that you could not keep 90 weight oil in there. I wrote them a letter informing them that mine had 90 weight in them, and they did not leak.
Shortly thereafter I quit reading that mag.......
Well I will find out soon enough, sold my truck and getting it this weekend sometime....guess I should pay the $20 so I can post pics....
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