Series gearbox with V8 engine

[Bigj66]

When using a Series gearbox with the V8 engine what is it that causes the failures we hear about? Is it simply a case of heavy right foot or is there a particular component within the box that is the weak link in the chain even when driven sympathetically?

 

[smallfry]

I have run several series 11a and 3s with both 3.5 Efi and 3.9 engines, one of them with a Fairey overdrive, and had no problems. Towing trailers too.

I think most of this stems from putting a V8 and an already knackered gearbox that has probably run with the wrong or no oil for years. Provided the bearings are OK, I don't think you will have much problem.

[Stellaghost]

I also ran a 3.5 v8 in my lightweight for 15yrs or so with no issues used to do modified trials with it and winch challenges still have the box took it out to put an LT77 in as not much of an off-road scene where I'm at now regards Stephen

 

[Team Idris]

S3 is weaker than S2a. The last crash-box has the biggest bearings. Normally they eat the rear diff. 

[Bigj66]

6 minutes ago, Team Idris said:

S3 is weaker than S2a. The last crash-box has the biggest bearings. Normally they eat the rear diff. 

Why the rear diff? Appreciate it’s taking all the load when in 2WD but is there something in particular about it that causes failures?

Could HD bearings be fitted to a S3 box to strengthen it?

[Snagger]

44 minutes ago, Team Idris said:

S3 is weaker than S2a. The last crash-box has the biggest bearings. Normally they eat the rear diff. 

No.  SII boxes have much weaker lay shafts which shear at circlip grooves or the ends of splines.  SIII lay shafts are massively stronger.  Earlier SIII units have 1st/2nd synchros which may be a bit weaker than the SII crash dog teeth, but Suffix D and E SIII boxes are the strongest used in 4cyl Series vehicles.  SIII boxes use the same bearings as late SIIA.  The transfer box is unchanged from the SIIA suffix C transfer box.

A V8 can have a lot more torque than a Tdi, depending on which V8 and how it’s tuned, but the smoother delivery from the petrol and it VP being V8 means less hammering on the transmission, so it seems the Series box tolerates the V8 better than a Tdi.  All the same, as long as there is nothing already damaged in the transmission and you don’t abruptly release the clutch pedal, you should have no problems with a V8 and standard transmission plus ONE of the following: overdrive; High Ratio Transfer Case; taller diffs or tyres.  There are several threads on that discussion that include the pros and cons of each.  If you add two of those mods, then you can expect to strip teeth off the main shaft gears after some time of accumulated fatigue.  If one of the mods is an overdrive, then as long as you only use it in fourth gear, you shouldn’t have any problems also running the taller diffs or tyres.

[Bigj66]

1 hour ago, Snagger said:

No.  SII boxes have much weaker lay shafts which shear at circlip grooves or the ends of splines.  SIII lay shafts are massively stronger.  Earlier SIII units have 1st/2nd synchros which may be a bit weaker than the SII crash dog teeth, but Suffix D and E SIII boxes are the strongest used in 4cyl Series vehicles.  SIII boxes use the same bearings as late SIIA.  The transfer box is unchanged from the SIIA suffix C transfer box.

A V8 can have a lot more torque than a Tdi, depending on which V8 and how it’s tuned, but the smoother delivery from the petrol and it VP being V8 means less hammering on the transmission, so it seems the Series box tolerates the V8 better than a Tdi.  All the same, as long as there is nothing already damaged in the transmission and you don’t abruptly release the clutch pedal, you should have no problems with a V8 and standard transmission plus ONE of the following: overdrive; High Ratio Transfer Case; taller diffs or tyres.  There are several threads on that discussion that include the pros and cons of each.  If you add two of those mods, then you can expect to strip teeth off the main shaft gears after some time of accumulated fatigue.  If one of the mods is an overdrive, then as long as you only use it in fourth gear, you shouldn’t have any problems also running the taller diffs or tyres.

Brilliant, thanks 👍

Back in the day I remember fitting RRC diffs to a V8 but to be honest back then I didn’t pay too much attention to road manners etc as it was all about the noise 🤷‍♂️😂

But something in my memory seems to think that we overcame the speedo reading issue by fitting the speedo drive gear from a LWB on 7.50s....🤔

Im not even sure if these were any different to the SWB speedo drives on the smaller tyres but it’s what we used to do. Does anyone know if there is actually any difference between them or was it just an old wives tale that I fell for? 🥴

[secondjeremy]

Series speedos all have the same drive gears in the gearbox - the difference being in the head.  SWB on 600 x 16 - or 205 x 16 have speedos with 1500 or 1536 Turns Per Mile, LWB's etc on 750 x 16's have 1408 and there are some others like 1376 or something for larger tyres.

The early S2 gearbox has a cut groove for 2 parts of a circlip to be inserted to keep the parts in place.  later on (1964???) Rover changed the shaft for an 'improved' version that looks much stouter.  In fact they may well have improved its snapping ability as they frequently snap at the 'reverse' end - where the shaft changes diameter.  Most of us who use lathes were taught that such a cut should be radiused to reduce stress - so Rover cut it square with a very sharp corner - and guess where it snaps.

Having said that from the boxes I've dismantled I'd say the true enemy is the springs in the 3rd/4th synchro unit (RTC1956) - which fall out when old and soft.  I'd suggest that if you have box apart for any reason that you change these springs as a preventative measure.  (They are a flat metal 'leaf' - and when they come out they tend to get between the gear teeth - which may be enough to break the layshaft.)

For an appreciation of the layshaft problem have a look at the old S2 club website where the subject was discussed by some apparently very knowlegeable people.

 

 

 

 

[Bigj66]

1 hour ago, secondjeremy said:

Series speedos all have the same drive gears in the gearbox - the difference being in the head.  SWB on 600 x 16 - or 205 x 16 have speedos with 1500 or 1536 Turns Per Mile, LWB's etc on 750 x 16's have 1408 and there are some others like 1376 or something for larger tyres.

The early S2 gearbox has a cut groove for 2 parts of a circlip to be inserted to keep the parts in place.  later on (1964???) Rover changed the shaft for an 'improved' version that looks much stouter.  In fact they may well have improved its snapping ability as they frequently snap at the 'reverse' end - where the shaft changes diameter.  Most of us who use lathes were taught that such a cut should be radiused to reduce stress - so Rover cut it square with a very sharp corner - and guess where it snaps.

Having said that from the boxes I've dismantled I'd say the true enemy is the springs in the 3rd/4th synchro unit (RTC1956) - which fall out when old and soft.  I'd suggest that if you have box apart for any reason that you change these springs as a preventative measure.  (They are a flat metal 'leaf' - and when they come out they tend to get between the gear teeth - which may be enough to break the layshaft.)

For an appreciation of the layshaft problem have a look at the old S2 club website where the subject was discussed by some apparently very knowlegeable people.

 

 

 

 

Cheers, that’s just reminded me that it was the speedo head and not the drive which we used to change.

Im pretty sure it used to bring the speedo reading back to within the legally acceptable tolerances of 10%.

[smallfry]

Mate has just reminded me. Geaxboxes were OK, but I got through a fair few rear halfshafts. RRC diffs.They always seemed to break at the diff end.

[Snagger]

On 3/15/2020 at 4:18 PM, Bigj66 said:

Cheers, that’s just reminded me that it was the speedo head and not the drive which we used to change.

Im pretty sure it used to bring the speedo reading back to within the legally acceptable tolerances of 10%.

Yep, the drive in the transfer box rear output is the same on all of them.  The speedo head has a four digit code on the bottom of the face denoting its application (tyre size, rather than specifically 88” or 109, as some 88s were built with the larger tyres), and mph or kmh.

[Team Idris]

On 3/15/2020 at 7:53 AM, Bigj66 said:

Why the rear diff? Appreciate it’s taking all the load when in 2WD but is there something in particular about it that causes failures?

Could HD bearings be fitted to a S3 box to strengthen it?

It is where diff pegging comes in. The torque makes the pinion ride the crown wheel due the carrier design. Salisbury takes it better than swb because it is bigger. 
the best fix was that shock absorber they fitted in the early rangy transfer box. It took the torque spikes out and that saved everything behind the flywheel. Don’t do burnouts  

[Gazzar]

Would a donut in the prop shaft have the same effect?

The ford Sierra used to have one.

[missingsid]

Im pretty sure it used to bring the speedo reading back to within the legally acceptable tolerances of 10%.

 

Except C&U regs were + or - 7% at that time! Now it seems it is any error as long as it reads faster than actual speed.

The 10% was what people thought plod applied!

Calculations showed that my S1 with 3.54 diffs and 7.50 tyres is somwhere like 30% out but that might include the Jag speedo not helping?

On the list to do is to conver to digital speed sender and classic look speedo as this can be programed for any ratio.