Rotoflex Engineer Owes Us Pints at the Pub

[jrsimpson]

Several weeks ago I purchased a '96 Disco 5 spd (my first LR). Despite the quirky engineering, leaks, etc., I enjoy the ride of the Disco and anxiously anticipate hitting the trail. Evidently, I've got the sickness. Before going off-road, I'm learning the feel of the truck and completing some minor repairs/upgrades. The previous owner, though not quite the proverbial little old lady driving back and forth to the bank, took good care of the vehicle, including professional maintenance. The first repair job I tackled on this previously underutilized Disco will come as no surprise to the experienced owners on this board: freeing a stuck center diff lock (CDL) linkage. My thanks to the tech DWebbers for thoroughly addressing the topic, especially this excellent link - http://home.twcny.rr.com/eeibooks/rover/discodifflock.htm.

My second project presents a greater challenge. A few days ago, I noticed a low rumble and slight vibration under load suggesting a problem in the driveline. A quick check underneath and on DWeb revealed the culprit: the dreaded rotoflex driveshaft coupler. Did some brilliant LR engineer actually believe that a thin piece of rubber would handle the amount of torque applied from the driveshaft to the differential? That S.O.B. engineer owes us all a pint for our trouble repairing this blunder. Perhaps we could all bring our old rotoflexes to the pub for use as coasters. Any creative ideas regarding what to do with this useless rubber?

Once again with the generous help of the DWeb tech section and previous posts, I'm on my way to upgrading the rear driveshaft with dual u-joints. I have successfully unmounted the driveshaft and ordered the appropriate upgrade parts. In the meantime, I need to drive the Disco. Several threads suggest that driving with just the front axle and CDL engaged (good thing I fixed this first) should be okay for the truck. I tried this on a short trip and despite some clunking upon engaging the clutch from a standstill, everything appears fine. I plan to drive only short distances at low speeds in this condition until the replacement parts arrive. Also, I've replaced the e-brake hub nuts and will check the retaining screw. Now to tackle the centralizing pin! Any comments, suggestions, criticism, and/or humor related to this project is appreciated.

Cheers,
Jeff

 

[flyfisher11]

number 8 metric bolt and a slide hammer!

 

[antichrist]

Sometimes heat to the pin is needed to free it.

 

[andrewv]

Lots of swearing and alcohol helps as well.

 

[andrewv]

Let me define lots: at least 6 hours worth.

 

[apg]

I've had a replacement Rotoflex waiting in reserve for at least 75,000 miles: it travels with the vehicle in the spare parts bag. The vehicle has about 125,000 miles right now, and the Rotoflex shows no signs of degredation - yet.

So...how long a job is it to swap out the coupling? Mind you, I won't have to fool with the bloody centering peg, as I won't be installing a U-joint just yet.

Cheers

 

[mightymg]

I have abotu 4 inches on my rover wiht 34 12.50s, and my roto lasted all of about 1 month, I replaced it with a spare during our MOAB trip, and that one lasted a whopping 2months, I now have a ujoint, and MAN DOES IT DRIVE GOOD> I WANT MY PINT!!

Ohh and my centralizing pin was being a bugger so I took my shaft off drove it to MY buddy at the dealer and he pulled just the plug out real quick wiht their tool in the parking lot, MAybe you can bribe a mechanic wiht a 12 pack and he will use 5 minutes and pull it for ya...

 

[jrsimpson]

Mike & Tom,
Thanks for the info on the pin thread (8mm diam, standard 1.25 mm pitch?) and the application of heat. First I'll heat it with a small MAPP gas tank, swearing all the while (drinking afterwards).

Sandy,
My '96 has just shy of 130k on it. Judging by the rounded nuts on the e-brake drum, this likely is not the first rotoflex failure. You're rotoflex is on borrowed time. In my naivete, I strongly recommend the upgrade. Nevertheless, replacing the rotoflex is a simpler job. Depending on your experience, available tools, etc., I'd estimate a couple of hours for the whole job. I had the shaft off in around an hour working outside my apartment without a jack. Here's the link to the tech section on the conversion http://www.discoweb.org/rotoconversion/index.htm

Also, having just completed the driveshaft removal, I can add a few tips.

1. Loosen the six rotoflex retaining bolts (19 mm or 3/4"). Note: a torn and hence distorted rotoflex complicates gaining access to the bolts. You'll likely need a breaker bar for this. Remove the bolts after loosening all of them.
2. Remove the four nuts on the e-brake drum. Note: a universal and extension helps gain access to these. Rotating the shaft allows clearance to fit a socket. I needed to remove the u-joint grease fitting to get a socket on one of the nuts.
3. Remove the grease fitting on the drive shaft. This allows much easier compression of the drive shaft (assuming regular grease maintenance), which is necessary for removal of the shaft.
4. Refit: should be the reverse procedure. I have not yet completed this step, hopefully there are no surprises.

Cheers,
Jeff

 

[KngTgr]

Yeah, after fighting for about two hours, I just gave up and took the driveshaft to a machine shop, and they removed it in 5 minutes flat

 

[justinhaaga]

i need to do this soon. anyone have other suggestions for the upgrade kit other than the $400 that atlantic bristish sells?

 

[p m]

Jeff, in a stock Disco, the rotoflex can last many tens of thousands of miles. The same rotoflex in LWB rangie lasts even longer, despite more weight and engine torque. Given the geometry of the Disco's rear suspension, the roto was the simplest and most efficient solution.

With 2" of lift, the donut lasts about 20-30kmi.

 

[bri]

I have abotu 4 inches on my rover wiht 34 12.50s, and my roto lasted all of about 1 month, I replaced it with a spare during our MOAB trip, and that one lasted a whopping 2months, I now have a ujoint, and MAN DOES IT DRIVE GOOD> I WANT MY PINT!!

Ohh and my centralizing pin was being a bugger so I took my shaft off drove it to MY buddy at the dealer and he pulled just the plug out real quick wiht their tool in the parking lot, MAybe you can bribe a mechanic wiht a 12 pack and he will use 5 minutes and pull it for ya...

You're lucky. I got on the gas in some scree. First time with 3" lift and new GBR shaft. I doubled the shaft bolts over the flange bolts.

Lasted about an hour. LOL.

I agree with P M. My first one lasted about 60k iles and finally gave out after a few months of wheeling when I got an OME lift.

Justin, forget AB, ggo GBR or such.

 

[jrsimpson]

Some prices on rotoflex to u-joint conversion:
1) British Pacific (shaft, flange, spacer, 4 bolts, 8 nuts separate): $315.11
I did not order from them simply because of shipping time to the East coast.
2) Rovers North, mix of genuine flange kit and other shaft: $340
3) D.A.P.: drive shaft & flange kit $349.95
4) Roverland Parts: shaft (used shaft and u-joints): $150. Would need flange kit from someone else (Atlantic British, British Pacific, Rovers North)

-Jeff

 

[p m]

if you value your time, buy a full kit from BP or RN, and don't mess with getting assortment of parts from everywhere (BTDT, with exactly this item).

 

[jrsimpson]

Peter, I was probably a bit facetious in my earlier criticism of the rotoflex. Nevertheless, a u-joint seems to me to be a relatively inexpensive and more durable solution. Was LR just cutting costs or do you think there's a deeper design issue?

I just checked the earlier maintenance records more thoroughly; The previous owner had an independent shop replace the rotoflex less than 10k miles ago. This suggests to me either mechanic error (seems unlikely on this relatively straightforward job) or another driveline problem causing the extremely premature rotoflex wear. Any thoughts on the cause? Should I start a new thread addressing this question in the disco tech discussions?

 

[p m]

I've been told a few times by land rover dealer techs that it doesn't matter how the roto is installed; it does, unfortunately; there are little triangles molded on the side of the rotoflex (near the bolt holes) meant to be arrows; they must be pointing to the "fingers" of the driveshaft and 3rd member yokes these holes are attached to. (I can't think of any really clear way of explaining it; if you hold a rotoflex with both hands, thumb, index, and middle finger covering the evenly-spaced holes on each side, the arrows on the side of the donut must be pointing to your fingers.) An incorrectly-installed rotoflex will break down very quickly.

If you look closer at the D1's rear axle geometry, you'll see that the trailing arms are longer than the A-link at the top. It means that the pinion angle is constantly changing throughout axle travel (unlike leaf-sprung vehicles, where it remains nearly parallel to the output yoke of the t-case). The solution to that is to use a CV joint - and you can think of a rotoflex of an inexpensive CV joint.
Sometime mid-year in 1997, LR engineers decided it wasn't that big of a deal, and replaced the rotoflex with a standard U-joint. Then, it came back with a D2, and it remained on range rovers until the end of P38 (am I right here?), for the same reasons it was used in the first place.

I believe there's a way to keep rotoflex happy even with the lift, using Rovertym's upper-arm spacer blocks (it'll tilt the pinion up).

Thanks for bringing this up, it gave me a chance to think it over once again.

 

[bri]

if you value your time, buy a full kit from BP or RN, and don't mess with getting assortment of parts from everywhere (BTDT, with exactly this item).

GBR sold me a kit. Just BTW.

 

[jrsimpson]

I found the little arrows on the rotoflex. Unfortunately, I did not mark the alignment prior to removal as I planned to convert to a 4-bolt flange for a u-joint. Hopefully the PO's mechanic just installed the rotoflex incorrectly and hence the extra short lifetime. Just in case, anything else I should check for signs of wear?

Do single u-joints (cardon joint) at each end of the rear driveshaft not provide enough hinge movement to compensate for the pinion angle change in a stock (or lifted) disco? As I understand, a single u-joint will handle around 15deg max of angular deviation. With a u-joint on each end of the driveshaft, that gives about 30deg total. CV joints allow a much greater angular deviation, approaching 80-90 deg., generally at a higher price. Should I have upgraded to a double cardon (DC) joint instead?

 

[flyfisher11]

I found the little arrows on the rotoflex. Unfortunately, I did not mark the alignment prior to removal as I planned to convert to a 4-bolt flange for a u-joint. Hopefully the PO's mechanic just installed the rotoflex incorrectly and hence the extra short lifetime. Just in case, anything else I should check for signs of wear?

Do single u-joints (cardon joint) at each end of the rear driveshaft not provide enough hinge movement to compensate for the pinion angle change in a stock (or lifted) disco? As I understand, a single u-joint will handle around 15deg max of angular deviation. With a u-joint on each end of the driveshaft, that gives about 30deg total. CV joints allow a much greater angular deviation, approaching 80-90 deg., generally at a higher price. Should I have upgraded to a double cardon (DC) joint instead?

Do yourself a favor and call Bill at Great Basin Rovers. This is his area of expertise and he doesn't mind explaining things to you.

(801) 486-5049

Good Luck,

Mike

 

[mightymg]

A driveshaft off a SWB rangie works great, THats what I used no problems!