Gearbox And Diff

[Guest salty_monk]

Chris, strange... you must have a particularly good engine. Ever put it on a rolling road?? Injection should be 115bhp as standard I think... (I know, you're going to tell me it's all down to the mechanic that built it right?? )

 

Paul, Road & Race transmissions are very good... They are close to Orpington. I had a quote from them for a recon LSD fitted into my casing with new bearings & seals for somewhere near £200+ (that was a 3.92) for your info the 4.27 LSD itself off the shelf (unbuilt into the casing) would be in the region of £400-£500 new!

The diff will not be a Viscous like the Sierra, it will be similar to a Quaife but one of the lesser known (according to Phil, much better quality) diffs...

 

4.27 is definitely going to make first pretty useless but will make the other gears good, you may find you run out of revs top end though.... (you'll definitely be able to find the red line in 5th..). If you can find a Capri box with the longer first gear you may find it a good combination... I discussed options with Phil & we sort of decided that a 4.1 may be the ideal.

It's interesting that they managed to machine the casting, I looked at doing that with one of these but didn't think the casting would be thick enough in a couple of places to allow it... Do you have any pictures of this one so I can see how they've done it for interests sake??

 

Phil (the owner there) has a Vauxhall 16v Cateringvan pulling about 240bhp as his personal toy... He's a nice guy & they come recommended, Drew has had some gearbox work done there before.

[Bob Tucker]

Just to add my 2d worth...

With the 3.62 I ran 115 in 4th, but only 105 in 5th

The 3.92 runs 105 in 4th & 115 in 5th..

 

On the 1/4 mile on Saturday I tried everything..

I set the wipers vertical

I turned the mirrors lengthways

I ran with & without the sidescreens

I ran with & without the Surrey top.

I ran with 35psi front tyres & from 15 to 28 in the rear.

 

There was no discernable difference with any setup!!!!

 

Unfortunately the 3.92 means I have to change into 4th to cross the line.

The 3.62 may mean less tyre spin at the start & I would cross the line in 3rd, saving a gear change. Anyway I now have a bench mark for the Pinto so I can measure the Vox 16V later this year.

Bob

[Shandylegs]

Hi

 

The info I have shows the following VIN Codes for Diff Ratios:

 

M=3.14

A=3.36

U=3.38

V=3.62

3=3.64

D=3.92

 

Therefore your diff will probably be a 3.64 not 3.38. 3.38's were generally fitted to all Autos and Oil burners of a later vintage.

 

Having driven Pinto powered RH's with 3.38, 3.62 & 3.92, I have to agree with all other comments that a 3.92 is really the only way to go (Especially if the engine is tuned).

 

Ta

 

Shandylegs :D

[Guest salty_monk]

Paul,

 

If you want my 3.62, check yours first. The way to do it is to mark the prop flange & measure how many times you turn it for one revolution of the output flanges.

If one output flange is locked (i.e. one wheel is on the ground) then you need to measure the number of prop flange revolutions to 2 revolutions of the single output (wheel). I know 3.38, 3.62 & 3.92 sound very close but actually it's quite obvious which it is using this method.

 

Dan

 

p.s. You're still welcome to a run out in mine of course...

[Peter Bell]

Salty don't get too obsessed with top speed, it does of course depend if you talking about what is shown on the speedo as opposed to what it really is doing and unless you know how accurate your speedo is you can only do it by engine revs, ratios and tyres.

Peter.

[Guest salty_monk]

No obsession, it just seems strange that Chris's car can push a bigger indicated speed than mine or Bob's when I assume it has less bhp as it's less modified.

My speedo is actually pretty accurate with the right diff fitted....

[Peter Bell]

Salty do you have the clamshell wings as per your avatar? If so Chris has cycle ones which will make a big difference in drag.

Perhaps this is heading for a RWYB day at Santa Pod?

Peter

[Guest RH-Track]

Hope this info helps on identifying, now you have two methods actually reading the numbers on the axle to check out vin plate

 

Diff ratios and Gearbox ratios

· Diffs

1.3 models = 3.77:1

1.6 models = 3.62:1 - saloon and hatch

1.6 models = 3.92:1 - estate

1.6 models = 3.38:1 - economy

1.8 models = 3.62:1 - 4 speed and auto

1.8 models = 3.92:1 5 speed

2.0 models = 3.62:1 - manual/carb

2.0 models = 3.38:1 - auto

2.0 models = 3.92:1 - manual EFi

2.0 models = 3.62:1 - Auto Efi

To identify the ratio in a particular diff, check out the Donor car. the third piece of data up from the left (Axle) will give a letter, this denotes the Ratio.

 

Vin plate Box 10 is the axle code.

 

M=3.14

A=3.36

V=3.38

U=3.62

3=3.64

D=3.92

· The following diff are LSD.

 

ALL 4x4 Sierra's and Granada's (2.8/9 and 2.0DOHC and Cosworth)

Most BUT not all 24v Cosworth Granada/Scorpio

All RWD COsworth Sierra (3dr, Saff, RS500)

 

· Identifying axle

There will be some numbers/letters (look at the top row),

 

EG. 83BG MC 362

 

The 1st set (83BG) is the case type (7" or 7.5") as there quite a few codes its not worth looking, the esiest way to ID a 7" and 7.5" is to look at the top mounting. The 7" has one long bolt/nut and the 7.5" has 2 bolts.

 

Next is the middle code in this case its 'MC' which is an 'OPEN' type diff (NON-LSD) basically ANY diff with 2 or more "A" in the middle code will be an LSD e.g. "AA" or "ADA" any other letters without an "A" in the code IS an open diff.

Finally is the numbers, 362 which is (simply) 3.62:1 ratio

[Guest originalMJG]

hi i am interested in getting a robin hood later this year and currently own a '91 2.0 DOHC sierra (carb) and thought i may be able to help (may).....

 

using standard size 185/65/14 tyres all around i can pull the following at around 5800-6000rpm (the redline).

 

~30mph in 1st

~60mph in 2nd

~95mph in 3rd

over 115mph in 4th

125mph in 5th is at about 4500rpm.

 

i understand aerodynamics is a major factor but maybe this could give you a basis for lengths of gears. i think i have the longer of the sierra diffs but going by the table earlier in this post you can tell what diff i have.

 

also some maths could work it out i suppose

 

HTH

 

Mike

[Guest docter fox]

i can get a speedo reading of 60 at about 6500 in 2nd and 90 in third at about the same using 185/65/13 tyres. tbh i dont trust the speedo at all and when cruising at 60 we seem to be going quicker than everyone else the extra inch wheel wouldnt make that much difference would it?

 

does it mean i have a 3.92 n a dodgy speedo or a 3.62 and a dodgy speedo

 

anyway.... what can people with a 3.92 get in the top of 2nd and 3rd? and does anyone have a gps thingy i can borrow?

[Guest klaxon]

Hi Paul

Form my own experiance I can tell you that my donor was 1986 2.0GL saloon.

The vin plate reads:-

Trans F....which I can confirm is a 5-speed

Axle V...which is as you guessed 3.38:1

I have bought a diff from a 1.6 estate in which the Vin plate read:-

Axle D....which is the 3.92:1

[Guest klaxon]

Hi Paul

Form my own experiance I can tell you that my donor was 1986 2.0GL saloon.

The vin plate reads:-

Trans F....which I can confirm is a 5-speed

Axle V...which is as you guessed 3.38:1

I have bought a diff from a 1.6 estate in which the Vin plate read:-

Axle D....which is the 3.92:1

[Guest Andybarbet]

My donor was an f reg 2.0l injection and it seems that more by luck than judgement, i have a good 3.92 diff.

And yes, Chris's car is very quick which is why i went for an injection engine donor and got rid of the 1.6 that i had.

[Snapperpaul]

Next job for me then is to drop the tank and have a good look at the diff, if it is a 3.38 then no point in going further with the build until i have corrected this.

I have my eye on a 2.0L DOHC 4x4 if it has a 3.92 then it will be on my drive in a week or two. Can i leave the subframe in place on my car and just swap the diff, halfshafts and discs. I have just fitted and sealed up the suspension covers on the Series 3.

Just to clarify 20L DOHC EFI 4x4 should be a 3.92 LSD and its code should be somthing like 83BG AA 392

[Guest Andybarbet]

If your running drum rears at the mo and convert to discs from the 4x4, the swing arms are slightly different. You can mod the drum arms but it may be easier to replace them from the 4x4 too if you have them ?