anthropoidape Posted March 3, 2007 Share Posted March 3, 2007 Hi everyone,Can anyone tell me whether the 2500 saloon diff is a bolt-in swap for a stag? I am finding the 3.7:1 diff ratio a little overgeared for my engine. I think that the 3.46:1 saloon ratio would be pretty good (even 3.2:1 would probably be better if only there were such a thing), and I have spotted one I can have quite cheaply.I'd welcome any advice here.Cheers,Jason Link to comment Share on other sites More sharing options...
wakaday Posted March 3, 2007 Share Posted March 3, 2007 It will bolt straight on with the Stag rear cover and propshaft flange swapped from the stag. Link to comment Share on other sites More sharing options...
DJT Posted March 3, 2007 Share Posted March 3, 2007 It may bolt straight in, but there were several different diff castings used across the Stag/2000/2500 range and one of them has 2 of the rear cover holes in a slightly different location, so you can only get 6 of the 8 bolts in. I have one 3.45:1 diff in my garage with this problem. I have used it with the 2 misaligned holes blocked off with an epoxy metal sealer and it doesn't leak.Dave Link to comment Share on other sites More sharing options...
anthropoidape Posted March 3, 2007 Author Share Posted March 3, 2007 Thanks very much gentlemen. I think I will acquire that diff! Link to comment Share on other sites More sharing options...
kritikon Posted March 17, 2007 Share Posted March 17, 2007 The saloon is only 3.46:1?Makes me wonder what diff I had fitted. :-/Around 4 years ago my diff went clunkity clunk. Couldn't source a Stag one, but the mechanic I used then got hold of a saloon one (can't remember which model exactly...I thought it was from a 2500 TC, but might well be wrong). He told me it was at a ratio of 4.1:1. Certainly after it was fitted it revved a tad higher...but the definite upside is that it actually pulls away at lights noticeably quicker up in 3rd. And the down side is that it revs slightly higher at top speed (which is a bugger while my overdrive is out of action >:().)What type of Triumph had a ratio of 4.1:1?I do remember he said he had to rejig it just a little to get it to fit, so probably it couldn't have been a straight saloon one. Hmmm....I think I must have an alien diff attached to my Stag. But it really does give it a bit more poke. I think I can almost get under 9 secs from 0-100kph with almost everything else as standard. :D Link to comment Share on other sites More sharing options...
DJT Posted March 17, 2007 Share Posted March 17, 2007 Stag diff - 3.7:1. Also used on, I believe, 2.5PI EstateOther big Triumph saloons - 3.45:1No idea what Triumph used 4.1:1. Certainly not the 2000.2500/Stag range.Dave. Link to comment Share on other sites More sharing options...
Deleted User Posted March 17, 2007 Share Posted March 17, 2007 4.11 all manual 2000's up to about 74? Then 3.7.3.7 all auto 2000's and above.3.45 all 2.5 regardless of transmission Link to comment Share on other sites More sharing options...
DJT Posted March 17, 2007 Share Posted March 17, 2007 [quote by=canleyclassics link=Blah.pl?b=stag,m=1172892312,s=6 date=1174115902]4.11 all manual 2000's up to about 74? Then 3.7.3.7 all auto 2000's and above.3.45 all 2.5 regardless of transmission[/quote]Thanks for that. To use a horrible modern cliche "every day is a school day".Are there any of the big saloon range that use the same diff carrier as the Stag? I am sure I read somewhere that the 2.5 estate did, but maybe I am wrong. I have a 3.45 in my Stag and this is built into an MG prefix casing which the Stag rear cover fits. I have another 3.45 diff (good but whines a bit around 50-60 mph) but the Stag rear cover does not fit properly as 2 of the bolt holes are mis-aligned.Dave Link to comment Share on other sites More sharing options...
Richard B Posted March 17, 2007 Share Posted March 17, 2007 There are differences between Stag and 2000/2.5 castings (hence the bolt mis-aligniment problem). But an Estate or MkI Saloon Steel back-plate will fit a Stag, thats what the car was based on (a MkI). So if you have a MkII Saloon diff that will not fit a Stag back-plate, look around for the rear casing from an Estate. Chris Witor always reckoned that the earlier diff mount was better for locating the differential; as it had more leverage than the Mk II Saloon and was less likely to twist in situ. Link to comment Share on other sites More sharing options...
Deleted User Posted March 17, 2007 Share Posted March 17, 2007 [quote by=Richard_B link=Blah.pl?b=stag,m=1172892312,s=8 date=1174138672]Chris Witor always reckoned that the earlier diff mount was better for locating the differential; as it had more leverage than the Mk II Saloon and was less likely to twist in situ.[/quote]Triumph knew it to that's why the MKII World Cup Rally cars reverted to a MKI type rear bracket arrangement, with major modification to the bodywork as a consequence. Link to comment Share on other sites More sharing options...
kritikon Posted March 18, 2007 Share Posted March 18, 2007 Quote:4.11 all manual 2000's up to about 74? Then 3.7.3.7 all auto 2000's and above.3.45 all 2.5 regardless of transmissionMany thanks. I really should have paid more attention at the time it was fitted. ;)Any harm likely from having the 4.11 diff fitted? As mentioned, it slightly increased the performance, which was good, but I never really delved into whether it was a good idea to actually do it...it was the only option at the time. Link to comment Share on other sites More sharing options...
nibby Posted March 18, 2007 Share Posted March 18, 2007 I have a noisy standerd diff on my stag which is a manual o/drive, in my garage i have a 3:4.5 diff.Would I notice a lot of difference if i put this on my car?Thanks in advance Link to comment Share on other sites More sharing options...
DJT Posted March 18, 2007 Share Posted March 18, 2007 [quote by=nibby link=Blah.pl?b=stag,m=1172892312,s=11 date=1174233921]I have a noisy standerd diff on my stag which is a manual o/drive, in my garage i have a 3:4.5 diff.Would I notice a lot of difference if i put this on my car?Thanks in advance[/quote]Your speedo will read 7% low assuming it is accurate now and you have standard tyres and wheels fitted, so watch out for speed cameras! You will also get approx 500 lower rpm at 70mph. Converseley your acceleration will reduce a bit, but you won't notice this unless you indulge in traffic light drag races.I have a 3.45:1 fitted to my Stag, but am running 15" wheels with 195/65 tyres. These are slightly smaller than standard, so this partially cancels out the above.Dave Link to comment Share on other sites More sharing options...
John Parker Posted October 15, 2007 Share Posted October 15, 2007 For any saloon or TR sports car diff into a stag use rear alloy plate with number 305721 cast upon it. Actual Triumph part number 134300 from estate cars or MK1 saloons,cheers jrparker@xtra.co.nz Link to comment Share on other sites More sharing options...
mikeyb Posted October 16, 2007 Share Posted October 16, 2007 I've just gone the other way around - from a Stag with 2.5 diff back to the proper Stag one. I think it feels a lot better through the gears than before (more natural) - the gear ratios never seemed quite right tallied up to the saloon diff.Also bear in mind that the stag diff internals are significantly more substantial than the saloon/estate internals! Link to comment Share on other sites More sharing options...
Spitfire2500 Posted October 16, 2007 Share Posted October 16, 2007 canleyclassics wrote:4.11 all manual 2000's up to about 74?I reckon 4.11 diffs must have been fitted for a while after that?The original bumpf that was supplied with our manual '76 2000TC says 4.11 final drive ratio and it certainly drives like a 4.11 ;D Link to comment Share on other sites More sharing options...
AlanChatterton Posted October 17, 2007 Share Posted October 17, 2007 All 2000's had 4.1All 2000/2500 auto's had 3.7All 2.5 manual had 3.45.All Stags are 3.7 (auto and manual)Stag diff and 2000 diffs look the same, but they are different. Stag diff is bigger and stronger case, has bigger sun and planet gear thrusts on it.However, it does share the same mountings as a MKI and all Estates, so you could put a 3.45 and bolt a MKI or estate back onto it and it will fit.Not strong enough though................You can fit a Stag diff into an estate or MKI, but to put it in a saloon you need a saloon backplate which is slightly different and has one stud missing, lots of gunge might seal it but it will leak forever.Stick to the diff you car model came with is the answer! Link to comment Share on other sites More sharing options...
wakaday Posted October 17, 2007 Share Posted October 17, 2007 I had a 4.11 in a Stag once. It came to me like that and it was an Auto. Great for the Traffic light Grand Prix. Shocking on fuel consumption.That was approx 10 years ago now and I passed it on as a resto project.Are you still out there LMA wearing your Yellow coat? Link to comment Share on other sites More sharing options...
John Parker Posted October 17, 2007 Share Posted October 17, 2007 The original stag CW&P has longer radial teeth,ie towards the middle,they are not taller.Beware of the pinion bearings between saloons and the stag case ( LD ) as the difference is only 20thou OD diameter.a real trap for the unwarey Link to comment Share on other sites More sharing options...
Deleted User Posted October 17, 2007 Share Posted October 17, 2007 Spitfire2500 wrote:I reckon 4.11 diffs must have been fitted for a while after that?The original bumpf that was supplied with our manual '76 2000TC says 4.11 final drive ratio and it certainly drives like a 4.11 ;DThe change to 3.7 in 2000 manual cars was contemporaneous to the plastic grille, dome top piston, 'commonized' 2.5 head, HS6 SU model. Ive had a few, proper slug's in comparison to the earlier model. I have the chassis number changeover points some where. Link to comment Share on other sites More sharing options...
Deleted User Posted October 17, 2007 Share Posted October 17, 2007 AlanChatterton wrote:All 2000's had 4.1All 2000/2500 auto's had 3.7All 2.5 manual had 3.45.All Stags are 3.7 (auto and manual)Nearly.Late 2000 manuals (plastic grille cars) are 3.7 (and no better for it).All 2.5 models regardless of transmission are 3.45. Link to comment Share on other sites More sharing options...
Spitfire2500 Posted October 17, 2007 Share Posted October 17, 2007 canleyclassics wrote:I have the chassis number changeover points some where.Any chance you can dig the info out Dave?I'm intrigued now. I've definitely got a plastic grill 2000 but I'm pretty certain it's got a 4.1 diff.Any way to tell quickly from the diff itself (S/No etc?) if it's a 3.7 or 4.1? Link to comment Share on other sites More sharing options...
Richard B Posted October 17, 2007 Share Posted October 17, 2007 Only by turning the input shaft and counting the number of times the output shaft turns. Link to comment Share on other sites More sharing options...
AlanChatterton Posted October 17, 2007 Share Posted October 17, 2007 There is usually a colour painted on the nuts of the output shaft, if you undo a driveshaft you can see either red, yellow or AN other colour.Can't remember what colour signifies what though......Anyone? Link to comment Share on other sites More sharing options...
Spitfire2500 Posted October 17, 2007 Share Posted October 17, 2007 GTEVO wrote:Result;- it can't even struggle up a 1:10 at 70 in OD and DRINKS even more fuel + can't overtake a moped!Sounds like I've probably got a 3.7 diff then.I'd put the sluggishness down to a slightly tired and off-tune engine and was reckoning on a 4.1 diff by (simplistically) comparing engine revs at indicated road speeds with the 2.5 Spit (3.63 diff).But ran the GPS in the Saloon during the trip into work this morning and discovered that the speedo in the Saloon is underreading by 10mph at an indicated 50 (actually doing 60) while the speedo in the Spit is absolutely spot on.Probably about right then -- indicated 50 in Saloon same as 60 in Spit so probably a 3.7 diff after all. :B Link to comment Share on other sites More sharing options...
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