10.25 Axle questions

[bikepilot]

I would like to change my gear ratios front and rear (4.10 to 3.55). I have a complete extra front end with the correct ratios and but to figure out what to do with the rear end. I was initially planning on just installing a new ring and pinion set, but am not sure I want to attempt it. Also I need to keep costs down as much as possible. I've worked on cars and trucks quite a lot (was a tech assistant for several years as I worked through high school/college), but never really got into any differential work. Any work would have to be done in my driveway, I have a decent set of hand tools and basic air tools. No specialty rear end tools though.

Being somewhat skittish about tearing into the rear end shortly before I need to leave on a trip, I start looking around for an entire rear end. I found one locally at a yard for about the same cost as a set of new gears ($275). Only issue is its an open diff (axle code 39). My current rear end is limited slip - would I be able to swap my LS unit in without messing with the gear lash etc?

I'm open to suggestions ideas etc. Keep in mind I have a limited budget and will be leaving for a trip to FL in a couple weeks. Would like to have it done before then, but not absolutely necessary. I'd also like to retain a limited slip rear and would like to think about adding a traction device to the front end before installing (lunch-box locker or LS??).

 

[JPR]

warning, the following is my opinion and not to be confused with facts.

What I have observed is that factory ring and pinion sets are very close tolerance. The majority of the shims are for tolerance in the carrier and the axle housing. You will notice that the factory gears are marked with something like +.002 or -.001. (There are charts that shows how to adjust the shims when swapping gears based on these numbers.) So with this in mind, you can swap gears without changing shims most of the time and get close on your contact pattern. Of course swapping a -.003 set for +.003 set will throw things off a bunch.

However, I have found that the swapping carriers to a different housing means readjusting the shim packs. Of the four axles that I have tried, only the Ford 8.8" in the Mustang was even close with the new carrier. The Dana 60 and two Chevy axles were way off.

Being somewhat skittish about tearing into the rear end shortly before I need to leave on a trip,
You mean there is another way?
By luck, it has happen that way on almost every major repair job I have done. Finish repair, shower, leave on trip, pray that everything gotten tightened up.

Suggestion? Swap in the whole axle for now and after the trip swap the carrier. Twice the work, but a little less worry.

On the front axle, avoid the LS and go with an ARB if you want drive with the hubs locked while on pavement. With the LS, it feels like you loss half of the power steering.

I was able to purchase a new Eaton LS for a third of the cost of the ARB so I went that route. The front LS really helps when the truck is stuck. I avoided being towed out of the mud this spring because of the front LS. Truck and trailer (loaded) were sitting on the axles. The front got a little traction and was able to drag itself out while the cat towed the truck that was ahead of mine.

 

[bikepilot]

Thanks very much for that info. I sent and e-mail to the yard with the axle in question and am waiting to hear back about mileage and such, but hopefully it will be decent and I'll carry out your suggestion.

For setting up the gears after the carrier swap, do I need any special tools? I have a dial indicator with magnetic base, but no gizmo to check bearing pre-load. Also, do I need any new parts on hand (crush sleeve and shims I assume) for when I do the carrier swap ?

I'm not averse to doing work just prior to a big trip, nor am I averse to trying something new (like setting up gears) but the combination of the two is a little worrying.

I remember when I was racing the local AMA off-road series (motorcycles) one night before a race I started tearing the top end down at 10pm. Fortunately its pretty simple and something I'd done several times before and I was sound asleep by 12:30 or so.

 

[JPR]

a basic install kit will have the shims, seals, but no bearings. A full kit "master rebuild kit will include the bearings.
4x4 parts
Do you have a copy of the Ford shop manual? If not I can send you a copy. It has good step by step instructions.

 

[sassyrel]

as jpr said--just swap wholer ear axle till get back--if knew what was doing--could have changed the gears before went--but probably only the rear set--unless your really fast--and good--remember--dont put the front end in gear with diff ratios!!! set the rolling torque before you put the pinion in--also--i changed mine over to a factory ls--just bolted the ring on the ls carrier--and put in--guess what--the backlash measured the same as the factory set!!!!!!! and the rolling tq was right--that dont happen very often!!!!!

 

[bikepilot]

I belive I have a Ford Shop Manual, but haven't pulled it out yet (I'm at work, it's at home). I'll look at it tonight though. If its really not all that difficult to get right, I might just skip the used rear end and buy a new ring/pinion/basic install kit for my current rear end.

I understand the idea of backlash, but could someone explain rolling torque? I assume that's the amount of resistance in the pinion bearings, but am not sure.

 

[bikepilot]

I checked and I do have a factory ford service manual that covers the rear end in my truck. Still waiting to hear back on the particulars of the potential replacement rear end.

Based on my perusing of the manual I'm less skittish of tearing into this thing than I was before. Looks like the only tool I don't have and would need is an inch pounds tq wrench and perhaps that special socket to undo the rear axle nut (on the Full Floater).

 

[160k87F250]

Hey, you said you had a couple front end axles. 4.10 or 3.55? Might want to trade a 3.55 for a 4.10. If you had a 4.10 front, that would be cool. I'm looking to convert mine to 4wd, We could trade the rears, and work out a price on the front. You interested?
John

 

[bikepilot]

Very well might be interested. My current rear is a full floater with ABS ring/speed sensor, limited slip unit with 4.10 gears. It has 126k miles on it and has been well maintaind at least since 80k (my dad bought it wtih 80k, previous owner seemed to have kept up the maintance too).

I would need the same basic unit (i.e. full floater with ABS stuff), only with 3.55 gears.

I have one complete extra front end that I plan nab the diff from. Once the front is swaped I'll have an extra complete front TTB system with 4.10 gears.

To be honest, if I were going to the trouble of a 4x4 conversion I'd hold out for a D-60 rather than the TTB D-50 system.

 

[160k87F250]

Mine should be the same as yours. Full floating, limited slip, ABS sensor in the center of the housing, 3.55 gears. Mine has 170,000 miles, though. But I bought the truck in 1999 with 123,000 and have changed the fluid and replaced axle seals and brakes. It will probably need rear brakes soon. It only gets driven 4000-5000 miles a year, now.
I would love to hold out for a straight axle. Actually, I would like to find a whole parts truck. I'm working on that. I was just throwing some ideas around.
John

 

[94f450sd]

no special tools needed to swap in a new gear set.ive done it countless times and never had one come back untill they wanted to try a new ratio.as long as your bearings are still good youll be fine.even then if you need/want bearings all you need to do is take it to a machine shop and have the press the bearings off and on.put the pinion in with a new crush sleeve and tigthen it slowly till there is no up/down side/side,in/out movement.it may turn a little hard but just back the pinion nut off till it turns easily with a small amount of drag on it.stake the threads on the pinion if you dont use a new nut. now put the carrier in with races and shim it till you have very little play in the gears.or run a piece of a brown paper shopping bag through the gears.you it to leave a nice impression of the gears teeth in the paper but not rip it.if it rips its too tight.

its alot easier than most think it is.my 1966 pontiac grand prix has been running around for 6years with the rear end setup just how i told you except i dont use the paper bag method.ive never had a problem or herd a noise from it.and that was even with a 600HP 428in it for 3 months.

 

[bikepilot]

Sounds good. I think I might give it a try. I have a frind who has done several that might be able to come over and help if I get stuck. All bearings and such should be good. I changed oil in the rear diff last year and haven't put more than 2k miles on the truck since. Everthing looked great at that time, just want to try a new raito.

160k87F250, Its an option, but I'd sorta like to hold onto my old stuff just incase I don't like the new raito. I think I'm going to try that route and if I have no luck I'll be up for swaping.

Thanks,

Josh

 

[Mr_Roboto]

IMO--- If you need the LS differential, you aren't saving anything by swapping in a whole axle assembly then swapping the differential.

I believe most of the R&P setup is using Prussin Blue dye and a lot of patience to get the contact pattern right. The better repair manuals have examples of what various contact patterns look like.

 

[160k87F250]

Hey Josh,
Thats cool. I've got alot going on right now, So it fine w/ me if you want to change the gears. I'd still be interested in your old parts when you know if your done w/ them.
John

 

[typ4]

look for the plus and minus marks on the pinion head, or the depth, if the old and new are within 3 or 4 thousandths original pinion shim thickness is ok, as per the dana manual, also holds true for every other gearset I have done. Several hundred. OMG. lol Side shims are external on the 10.25 so a wrecking yard I use always lets me use thier can o' shims to set my fords up. Pinion is just a light drag and I recheck in a thousand or so miles.
The paper bag trick was told to me when I was but a youngin, 16, by a 89 yo mechanic that has forgot more than I will ever know. if it cuts the bag, too tight, just a hard crease is fine, I have measured this with an indicator and it always is right in the spec, gotta love those old timers!!!!
BTW I really like this forum.
Hope this helps, Russ