Flippin' Differentials

[MerlynIIa]

I had read a couple of years ago in a Land Rover magazine of an old trick for "refreshing" a Series vehicle --- you could swap your front and rear diffentials. Since each would then be moving in reverse of what it had been, you have a less worn surface and potentially quieter operation. that way you could esentially get double wear from the diffs!

Has anyone done this before? I thought it seemed logical, provided the differentials weren't too shot and would like to give it a try when putting my Series III back on the road.

thanks!

[daveb]

sounds like a waste of time. I think most of the noise is from the engine/trans/tires/wind.



I had read a couple of years ago in a Land Rover magazine of an old trick for "refreshing" a Series vehicle --- you could swap your front and rear diffentials. Since each would then be moving in reverse of what it had been, you have a less worn surface and potentially quieter operation. that way you could esentially get double wear from the diffs!

Has anyone done this before? I thought it seemed logical, provided the differentials weren't too shot and would like to give it a try when putting my Series III back on the road.

thanks!

[Eric W S]

Noisy diffs would indicate a set up or bearing issue.

Flipping them doesn't make the diffs any newer. I'd say spend the money and rebuild them properly.

If it sounds to good to be true, it probably is...

[I Leak Oil]

When pulling diffs out of parts trucks, I'v found the front is generally in better condition, especially if the truck had FWH's. The reason is obvious, the front usually lives most of it's life in a "coast" condition where in rarely see's power from the transmission. This is just my general observation and not a steadfast rule. If you need to replace a diff. then you're usually better off trying to find one out of the front axle, but a good diff is a good diff. Swapping them just to gain a little longevity?....You're better off just making sure it's filled with oil.
My 2 cents.
Jason T.

[Daurie]

Since each would then be moving in reverse of what it had been, you have a less worn surface and potentially quieter operation. that way you could esentially get double wear from the diffs!



thanks!

You wording leads one to assume the diff would be acutally turning the opposite/ reverse direction if you swapped them. Not the case. All you would be accomplishing by swapping the diff front to rear is using a less worn one in the back an giving the back a little break by residing in the front.. I too think you'd be better of just giving the rear a little more TLC if it's a concern. If it's unusually loud I'd suspect a problem that wont go away just by swapping it to the front. :thumb-up:

[LaneRover]

I would agree that if a Series Rover had done many miles on road then swapping the diffs front to back would work to give you the better of the two diffs out back. I would definitely recommend this as something to try to someone whose money is tight.

Would a rebuilt diff be better? Yes. But for someone who doesn't off-road much and just needs to get their truck back on the road then I say flip the diffs.

My opinion

Brent

PS Having FWH doesn't necessarily help. What if the person with the Rover NEVER locked the hubs for lubrication? Is there a chance that the top half of the ring would be pitted? No matter what inspection of said items would be good.

[JSBriggs]

You wording leads one to assume the diff would be acutally turning the opposite/ reverse direction if you swapped them. Not the case. All you would be accomplishing by swapping the diff front to rear is using a less worn one in the back an giving the back a little break by residing in the front.. I too think you'd be better of just giving the rear a little more TLC if it's a concern. If it's unusually loud I'd suspect a problem that wont go away just by swapping it to the front. :thumb-up:

It is the case. To go forward: The relative rotation of the pinion in the diff housing in front turns CCW while the rear turns CW. The rear is pushing on the 'drive' side while the front pushes on the 'coast' side. This is why the rear diff is 'stronger'


I would agree that if a Series Rover had done many miles on road then swapping the diffs front to back would work to give you the better of the two diffs out back. I would definitely recommend this as something to try to someone whose money is tight.

Would a rebuilt diff be better? Yes. But for someone who doesn't off-road much and just needs to get their truck back on the road then I say flip the diffs.

My opinion

Brent


I would agree. Its like rotating tires to get the most out of them. But if the wear is enough to cause slop or noise, then it needs to be rebuilt. If you only need 4wd for occasional light duty use it will probably be ok, but running a worn diff in the front (weaker position IE pushing the coast side) is likely to chip teeth or worse during moderate to heavy offroading.

-Jeff

[MerlynIIa]

Hello again, spirited discussion! Thought I would quote the article that led me to ask about this in the first place. The article is in the December, 2006 Land Rover Monthly. On page 145, discussing the refurbishment of a Series III, a mechanic stated "The differential on the front axle was in good shape, although the one on the back was rather noisy, worn and beyond acceptable tolerances. However, I managed to reuse both by swapping them around from front to back and back to front. this was okay, as they were then working in the opposite direction, so the working surfaces were still unworn. And although the rear diff which was now fitted to the front had seen a lot more wear through being constantly engaged whenever the vehicle was in motion, this didn't matter very much, as from then on it would only come into play when four-wheel-drive was engaged, with power then delivered to the front axle. this saved Toby some money, as a good second-hand diff cost about 80 pounds rising to about 300 pounds for a new one."

I think, while checking the diffs I have, I may shoot for using the front diffs out of both my Series III and my Series IIa donor vehicle. That way, they would be the most likely to check out ok and have the least wear.

Thanks

[Eric W S]

Why don't you just rebuild them? Your going to have them out anyway and if they aren't in that bad a shape a rebuild kit with all the bearings and seals will solve your problems. Seems like your trying to justify not rebuilding one using a magazine article and other parts from other trucks. Mountain out of a mole hill.

[Daurie]

I guess I stand corrected! I would have never guessed that. After thinking about it theres no other way it would work and be the same ring and pinion and pinion carrier front to rear. :rolleyes:

[109 Pretender]

Flipping diff's over seems to be fairly common on Pirate 4x4, but I've read that you do need to be concerned about adequate lubrication for the pinion bearing. The Rover design is the venerable spiral bevel which wouldn't be as sensitive as a low pinion hypoid being flipped over to make it a high pinion type. (This is done when needing to change the driveshaft angle and for more ground clearance). From what I understand most custom flip jobs have some mods done to improve oiling for the pinion.
But as almost everyone has mentioned - if it's really that worn you might consider getting a couple of good used 3rd members instead. You should also inspect your drive splines and flanges as these areas usually wear out first and may need attention too.

Good Luck!

[JSBriggs]

Flipping diff's over seems to be fairly common on Pirate 4x4, but I've read that you do need to be concerned about adequate lubrication for the pinion bearing. The Rover design is the venerable spiral bevel which wouldn't be as sensitive as a low pinion hypoid being flipped over to make it a high pinion type. (This is done when needing to change the driveshaft angle and for more ground clearance). From what I understand most custom flip jobs have some mods done to improve oiling for the pinion.
But as almost everyone has mentioned - if it's really that worn you might consider getting a couple of good used 3rd members instead. You should also inspect your drive splines and flanges as these areas usually wear out first and may need attention too.

Good Luck!

'Flipping' or rotating the diff 180° is different than swapping front to rear. There isn't any benefit to rotating a rover diff (spiral bevel) as the pinion is contacting at the centerline of the ring gear. Its on hypoid gears where the pinion contacts below the centerline that there is any clearance gained by rotating it in the housing. Once rotated the pinion is then contacting above the centerline of the ring gear and gives more clearance/better driveling angles. This is what creates the oil starvation issue on the pinion bearings as it is no longer submerged in oil.

-Jeff

[109 Pretender]

Sorry Jeff! Guess after reading my msg. I wasn't very clear. Yes, the spiral bevel design doesn't need to be flipped - just 'turned around' so to speak. The problem becomes this - the ring gear is like a 'paddle wheel' to the gear lube. Rotated one direction it 'pushes' lube into the pinion area of the housing. Rotated the other way, it 'pulls' the lube away - with perhaps premature wear of the pinion bearings due to oil starvation. The rock crawler group has dealt with this for some time because they build some extreme rigs. Some case manufacturers have built custom cases for these situations - modifying the oil passages to alleviate the problem. I know the front/rear cases are different externally - just don't know if the oil passages would be diff. OR if it would cause a problem in this application. Thought I might throw this detail into the big pic for consideration.

Cheers!

[109 Pretender]

Here's an interesting excerpt I found on the web you guys might enjoy readingsince we're talking swapping diffs: (It's kinda long...) It also does a good job of explaining Bill Davis's (GRB) Rover front diff. mod - he pins the ring gear to make better contact with pinion gear.

Reverse-Cut vs. Standard-Cut:
Often mistakenly referred to as "reverse rotation," the term "reverse-cut" is perhaps the single most misunderstood term by four wheelers and even many in the axle business. A reverse cut housing is not just like a standard cut housing turned upside down. It is a specially designed housing for front driving axles. Contrary to popular belief, it does not turn backwards or in reverse. The term "reverse-cut" actually refers to the direction of the spiral cut in the ring gear.
In a reverse cut axle, the spiral on the ring gear is opposite form a standard -cut ring gear. The idea behind reverse cut is to strengthen the operation of the gear when it is used for a front axle application.
http://katy.tx4wd.org/tech/general_axle_info/reverse_vs_std.gifIn the early day of four wheel drive, the front axle used the same gears and housing as an ordinary rearend. This was done for economic reasons, since the components were already in mass production. They simply added the necessary parts to enable steering. However, all ring and pinion gears are cut in such a way that they are inherently stronger when pushing the vehicle in the forward direction and weaker when driving in reverse. That means that a standard cut (rearend style) gear, when used in the front, must push on the weaker side of the gear to move the vehicle in a forward direction.
This practice continued until the late 1970s, when Dana designed a new axle that would be stronger for front axle use and also provide better driveline angles for the shorter front driveshafts then being used in new trucks. The reverse cut housing and reverse cut gear set can be identified by the pinion gear, which is located above the centerline of the axle shaft. Therefore, standard cut gears are always strongest when used in rear axles and reverse cut gears are stronger when used in front axles.
Reverse cut axles have also become popular for lifted short wheelbase vehicles like Jeeps, early Broncos and Land Cruisers. The reason is because the higher pinion location greatly reduces rear driveshaft angles. However, not all reverse cut axles are strong enough for use as a rearend. The cut of the gear that makes them stronger for the front axle use also makes them somewhat weaker for the rear axle use. The best and most popular reverse cut axle for rearend use is the Dana 60, a good choice because of its large ring gear diameter, tooth strength, ability to accept 35 spline axle shafts and wide selection of ratios and differentials.
Two other reverse cut axle are the Dana 44 and a new Ford 8.8" reverse cut. The Dana 44 makes an excellent front axle, but just isn't strong enough for rear axle use. The Ford 8.8", reverse cut rearend (new from Currie Enterprises) has a slightly larger ring gear than the 8.5" of the Dana 44 but is not nearly as strong as the Dana 60, which has a 9.75" ring gear. The new 8.8" uses a special third member that bolts into a removable carrier Ford 9 inch housing and its sometimes mistakenly referred to as a reverse cut Ford 9 inch. Both the Dana 44 and the ford 8.8" can accept a maximum of a 30 to 31 spline axle shaft.
The bottom line is that reverse cut gears (front axle style) and axle assemblies are inherently stronger for front axle use because of the way the gear mesh when moving the vehicle forward direction. They also provide better driveline angles because the pinion is located above the centerline of the axle. The gear set used in each type of axle are not interchangeable. Standard cut gears cannot be used in place of reverse cut and vice versa. The housings are also not interchangeable. However, differential cases, be open, limited slip or locker are compatible with both styles, as long as the spline count matches the axle shaft.
-Reverse-Cut vs. Standard-Cut taken from FourWheeler January 1999

[MerlynIIa]

I want to thank everyone for the great input and discussion, where ever it leads! Thats how I learn. As to my motivation for the original post. I found the article unusual and wanted to see if swapping diffs was common or not and if the logic was sound. I have enjoyed it when others bring unusual topics to the forum, especially when a lively debate ensues.

Everyones' own vehicle work is a combination of time, money, talent and preference. We all have to balance those as we see fit and the forum helps with that.
As I am planning my work to get my Rover on the road, I do not have the time nor the money to do a ground up, though I would enjoy it greatly. Unless you are doing the full resto, then one has to make decisions about what to tackle in depth and what to use as is. I am going to protect the chassis and lower bulkhead, probably rewire and renew all seals and damaged parts. Parts that seem good and are not difficult to pull from the completed vehicle later may get less attention than parts that are difficult to address unless the Rover is stripped down. I have no doubt that my plan will change many times as I go along.
Thanks for all and I have greatly enjoyed the discussion!