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Gearboxen

2K views 34 replies 10 participants last post by  ferkle 
#1 ·
Right then... I am having thoughts and they might be some of the most silly thoughts on the planet, so bear with me....

Can't remember where, but somewhere on this forum i read that the designation for the 5 speed manual 'box is F25 - which is one of the designations that Vauxhall use - another GM stable, would I be correct in saying that this designation is due to both boxes being the same unit?

First silly question over.

Next one, if this is the same unit, and hypothetically speaking I were to be in the market due to need or want to change my tranny (obviously with our trannies being so bulletproof we never need to make these considerations:roll: ) would I be able to drop the (significantly cheaper to get hold of) Vauxhall F25 in, or if i were feeling adventurous, the 6 speed F28 box should the ratios be suitable - subject to calculating etc.

Just a thought, not a plan. Although I have come to like this GM thing, I have found a few bits and bobs out there that are cheaper because they dont have Saab stamped on them....

I figure this is a performance question because if the latter idea works out well, it would surprise me if a bunch of 6 speed 900s didn't turn up if the ratios worked out for either/or better acceleration/top speed.

Something to think about there. (and it will get those pesky vauxhall tuners back, they apparently steal all our parts from what i hear!!)
 
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#2 ·
if it fits, that would be cool, strap that to a 3.0
 
#3 ·
yup, Well it should go straight on the 2.5 as it is the same engine/box and i beleive the 3 litre is the same bottom end with different bores.


I am hoping to see if anyone knows about the 2 litre turbo.... I am looking at specs etc.
 
#4 ·
ferkle said:
yup, Well it should go straight on the 2.5 as it is the same engine/box and i beleive the 3 litre is the same bottom end with different bores.


I am hoping to see if anyone knows about the 2 litre turbo.... I am looking at specs etc.
i would sell my right arm for a 6 speed tranny for my car... but then i would need to get a new car and move out of the states (right hand drive cars for all of you who didnt get my lame joke)
 
#5 ·
F25 tranny in a Vauxhall was supplied to them from Saab.

The gearbox in theory could be made to go one way or the other, the Vectra F23 could go to yes? and in theory so could the 6 speed F28 [a seriously tough bit of kit from Getrag] also.

So what you'll then need to fork out on is getting Trionic to accept the Vauxhall final drive ratios [5 speed] or the 6th gear's existence. So some way around boost control and limp home mode is required - good quality MBC or a trick ECU re-write. If you had a V6 it would be simple plug 'n' play :lol:
 
#7 ·
ferkle said:
Right then... I am having thoughts and they might be some of the most silly thoughts on the planet, so bear with me....

Can't remember where, but somewhere on this forum i read that the designation for the 5 speed manual 'box is F25 - which is one of the designations that Vauxhall use - another GM stable, would I be correct in saying that this designation is due to both boxes being the same unit?

First silly question over.

Next one, if this is the same unit, and hypothetically speaking I were to be in the market due to need or want to change my tranny (obviously with our trannies being so bulletproof we never need to make these considerations:roll: ) would I be able to drop the (significantly cheaper to get hold of) Vauxhall F25 in, or if i were feeling adventurous, the 6 speed F28 box should the ratios be suitable - subject to calculating etc.

Just a thought, not a plan. Although I have come to like this GM thing, I have found a few bits and bobs out there that are cheaper because they dont have Saab stamped on them....

I figure this is a performance question because if the latter idea works out well, it would surprise me if a bunch of 6 speed 900s didn't turn up if the ratios worked out for either/or better acceleration/top speed.

Something to think about there. (and it will get those pesky vauxhall tuners back, they apparently steal all our parts from what i hear!!)
You can use any tranny if you use an adapter plate to mate the engine and tranny together.
 
#8 ·
A definitive answer would be nice. The inner driveshaft joints are very different on Saab turbos. Don't know about the splines.

Gearbox No3 is showing signs and making noises.

So if it's a bolt on job with no strange adaptor plates, cut driveshafts, odd clutches, different clutch releases and cables, engine mount, special linkages, equal length driveshafts and bearing. etc. etc. Then I'm very soon in the market for one.

There's a few things that they may have changed..........................

[Wasn't deliberately sarky, just sort of turned out that way ;oops: ]
 
#9 ·
hunt.dogshome said:
A definitive answer would be nice. The inner driveshaft joints are very different on Saab turbos. Don't know about the splines.

Gearbox No3 is showing signs and making noises.

So if it's a bolt on job with no strange adaptor plates, cut driveshafts, odd clutches, different clutch releases and cables, engine mount, special linkages, equal length driveshafts and bearing. etc. etc. Then I'm very soon in the market for one.

There's a few things that they may have changed..........................

[Wasn't deliberately sarky, just sort of turned out that way ;oops: ]
I thought the V6 had the same shafts as the turbo :confused:

The clutch is my concern.

One piece of advice I think may be worth offering, once you go past the torque numbers Saab were prepared to put through the transmission consider the fluid as a service item rather like engine oil as it will be heat damaged.
 
#11 ·
so anyone find anything out about putting that 6speed on a 2.0?
 
#13 ·
i really want a six speed, and mayb we will get some better gearing out of this deal:p
 
#15 · (Edited)
I have my friendly local vauxhall nut on the case.


he also has 2 f28 6 speeders in his shed(so i understand at least)..... if i find this to be suitable, I may very well go ahead and try to make a change early next year, I originally posted as these units are dirt cheap relatively speaking, and figured if anyone knew off the cuff it would be a good investment, or at least a relatively easy swap, as raggy posted earlier the f23 5 speeder (as found on our vauxall cavalier/luton limo chassis brothers) may be a more likely option, and as it doesn't say saab on it, these are cheaper to obtain also!! the other reason is that the wierd noise i was getting a couple of weeks back was partly idler pulleys and also 'something' that isn't camchain as such i have listened a lot and had people hang out of te passenger window in a carpark and it does smack of gearbox unpleasantness, story of our lives eh!!

my original thoughts that the 'f' gearboxes might be bolt ons were due to my reading somewhere that the 900 5 speed is an f25 unit, and this clicked about a week later, as with vauxhalls the f series boxes, so far as i am led to beleive, are straight fit onto most vauxhall motors...

anyway i will keep posting as and when i know more.

just to get the thinking fluids going, does anyone have the ratio/final drive specs for the f25 found in our cars?
 
#16 ·
ferkle said:
I have my friendly local vauxhall nut on the case.


he also has 2 f28 6 speeders in his shed(so i understand at least)..... if i find this to be suitable, I may very well go ahead and try to make a change early next year, I originally posted as these units are dirt cheap relatively speaking, and figured if anyone knew off the cuff it would be a good investment, or at least a relatively easy swap, as raggy posted earlier the f23 5 speeder (as found on our vauxall cavalier/luton limo chassis brothers) may be a more likely option, and as it doesn't say saab on it, these are cheaper to obtain also!! the other reason is that the wierd noise i was getting a couple of weeks back was partly idler pulleys and also 'something' that isn't camchain as such i have listened a lot and had people hang out of te passenger window in a carpark and it does smack of gearbox unpleasantness, story of our lives eh!!

my original thoughts that the 'f' gearboxes might be bolt ons were due to my reading somewhere that the 900 5 speed is an f25 unit, and this clicked about a week later, as with vauxhalls the f series boxes, so far as i am led to beleive, are straight fit onto most vauxhall motors...

anyway i will keep posting as and when i know more.

just to get the thinking fluids going, does anyone have the ratio/final drive specs for the f25 found in our cars?
Anyone a little help? I have no clue myself...
 
#17 · (Edited)
I just found this (see below) which is handy. Formatting is out a bit.

Code:
Gearbox 1st 2nd 3rd 4th 5th 6th rev FDR
========================================================
F10/F13 3.55 1.96 1.3 0.89 0.71 3.31 4.18
F16w 3.55 1.95 1.28 0.89 0.71 3.33 3.94
F16c 3.55 2.16 1.48 1.13 0.89 3.33 3.55
F18w 3.58 1.87 1.23 0.92 0.74 3.33 3.55
F18c 3.58 2.14 1.48 1.12 0.89 3.33 3.55
F20(3.55) 3.55 2.16 1.48 1.13 0.89 3.33 3.55
F20(3.72) 3.55 2.16 1.48 1.13 0.89 3.33 3.72
F23 3.58 2.02 1.35 0.98 0.81 3.31 3.84
F25 3.38 1.76 1.12 0.89 0.77 3.17 3.82
F28 3.57 2.16 1.45 1.1 0.89 0.74 3.32 3.72

So there we go. I will continue to search ignoring http://www.quaife.co.uk/catalogue/page61.htm because it is too painful!!
:cool:
From a few searches trying to obtain the ratios on the F25 that we use, it appears to be the same as the f25 listed above - there are apparently

Anyone know the maths to work out how this translates into speed per rpm or whatnot? (I will keep searching after dinner, however at the moment my stomach takes precedence!!)
 
#18 ·
ferkle said:
I just found this (see below) which is handy. Formatting is out a bit.

Code:
Gearbox 1st 2nd 3rd 4th 5th 6th rev FDR
========================================================
F10/F13 3.55 1.96 1.3 0.89 0.71 3.31 4.18
F16w 3.55 1.95 1.28 0.89 0.71 3.33 3.94
F16c 3.55 2.16 1.48 1.13 0.89 3.33 3.55
F18w 3.58 1.87 1.23 0.92 0.74 3.33 3.55
F18c 3.58 2.14 1.48 1.12 0.89 3.33 3.55
F20(3.55) 3.55 2.16 1.48 1.13 0.89 3.33 3.55
F20(3.72) 3.55 2.16 1.48 1.13 0.89 3.33 3.72
F23 3.58 2.02 1.35 0.98 0.81 3.31 3.84
F25 3.38 1.76 1.12 0.89 0.77 3.17 3.82
F28 3.57 2.16 1.45 1.1 0.89 0.74 3.32 3.72

So there we go. I will continue to search ignoring http://www.quaife.co.uk/catalogue/page61.htm because it is too painful!!
:cool:
From a few searches trying to obtain the ratios on the F25 that we use, it appears to be the same as the f25 listed above - there are apparently

Anyone know the maths to work out how this translates into speed per rpm or whatnot? (I will keep searching after dinner, however at the moment my stomach takes precedence!!)
This would be a start:
http://en.wikipedia.org/wiki/Gear_ratio
 
#19 ·
well since im at school i cant acess this, but they have a ratio converter on there website, http://www.quaife.co.uk/products/gearkits.asp you have to register, takes 30 sec, then you can access the converter, i wonder howmuch this would cost, and where reverse would end up being? maby waaaaay right and down or idk any thoughts
 
#20 ·
#21 ·
ok, i am very ready to be corrected but here goes based on stock 16" wheels - on 215/45 x 17at 100mph indicated, actual speed is around 102mph

F25 (3.82:1 final drive at 5900rpm)

1st/3.38 = 32.7mph

2nd/1.76 = 62.9mph

3rd/1.12 = 98.7mph

4th/0.89 = 124.3mph

5th/0.77 = 143.6mph

And F28 (3.72:1 final at 5900rpm, same wheels)

1st/3.57 = 31.8mph

2nd/2.16 = 52.57mph

3rd/1.45 = 78.3mph

4th/1.1 = 103.2mph

5th/0.89 = 127.6mph

6th/0.74 = 153.4mph

Looking at these calculations I suspect that day to day the box might be a bit frustrating.... still if the bellhousing bolts up and the clutch isn't too big an issue I am still fairly keen.

I have also read that the 5 speed f20 units are strong, capable of handling big torque numbers - all of them will happily hold 350bhp apparently.... .much more than I inend to run!!
 
#23 ·
ferkle said:
F25 (3.82:1 final drive at 5900rpm)

1st/3.38 = 32.7mph

2nd/1.76 = 62.9mph

3rd/1.12 = 98.7mph

4th/0.89 = 124.3mph

5th/0.77 = 143.6mph
thats not our cars now is it? that cant be right i was going 140 in 5th andwas at 5100-5200
 
#24 ·
what one would it be with the 6 spd trany
 
#25 · (Edited)
jonny72888 said:
thats not our cars now is it? that cant be right i was going 140 in 5th andwas at 5100-5200
Jonny, if you are absolutely sure about your (uncorrected/speedo or trap? makes calculations innacurate either way) speed compared to indicated RPMs I get the following.

Ok, by playing with a few numbers puts final at around a 3.52:1 @ 5200rpm to get 140mph

I don't know this for sure, nor have I found an official resource to back any of this up (i.e. do not shoot the messenger, unless you have correct figures, information ... I have worked 'king hard to get this far:) ) i figure the final drive (differential gear) must be different on our cars....
The reason I think this is that these are the figures for the stock gm f25 and stock gm f28 side by side (see the figures above) knowing that our cars use the gearbox designation f25 and are made my gm, I have simply added 2+2 and am hoping for 4 as a result.

I am definitely no expert on this thus the original question. :cool:

Again, I am working from figures found on the internet for Vauxhall specs, not Saab specs... if anyone can help with real actual ratios and final drive i will gladly do the maths.

tbuck

F28 (3.72:1 final at 5900rpm, same wheels)

1st/3.57 = 31.8mph

2nd/2.16 = 52.57mph

3rd/1.45 = 78.3mph

4th/1.1 = 103.2mph

5th/0.89 = 127.6mph

6th/0.74 = 153.4mph

these are the f28 without making final drive changes. bear in mind also that the f28 is designed as an awd gearbox, so will need mods (i.e. fabricating or purchasing a plate to go over where the transfer box would usually sit and whatever else needs doing, there are a bunch of companies that supply parts to do this for vauxhalls obviously I will look further into this when proof of concept is more tangible.)
 
#26 ·
ferkle said:
i figure the final drive (differential gear) must be different on our cars.... these are the figures for the stock gm f25 and stock gm f28 side by side

which by running a few numbers puts final at around a 3.52:1 @ 5200rpm to get 140mph

again, I am working from figures found on the internet for Vauxhall specs, not Saab specs... if anyone can help with real actual ratios and final drive i will gladly do the maths.

tbuck

F28 (3.72:1 final at 5900rpm, same wheels)

1st/3.57 = 31.8mph

2nd/2.16 = 52.57mph

3rd/1.45 = 78.3mph

4th/1.1 = 103.2mph

5th/0.89 = 127.6mph

6th/0.74 = 153.4mph

these are the f28 without making final drive changes. bear in mind also that the f28 is designed as an awd gearbox, so minor mods (i.e. fabricating or purchasing a plate to go over where the transfer box would usually sit)
or just make the saab awd:D
 
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