Jim1 Posted December 25, 2011 Share Posted December 25, 2011 I have got 1988 defender with a 300tdi + lt77 + original T/box top speed 40mph. I would've expected to get 50ish. If I change T/box to a disco T/box will this give me a better top speed. I'd like 60mph. Engine is fine, gearbox/T.box fine Just don't understand speed restricted to 40mph engine is over revving. Any ideas why speed issues. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted December 25, 2011 Share Posted December 25, 2011 Sounds like you are stuck in low range !!!! or a seriously under reading speedo ? Quote Link to comment Share on other sites More sharing options...
farmerboy_y2k Posted December 25, 2011 Share Posted December 25, 2011 Could be a 1.6 ratio transfer box but that would still get to over 60. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 25, 2011 Share Posted December 25, 2011 You sure its not in low range? Quote Link to comment Share on other sites More sharing options...
western Posted December 25, 2011 Share Posted December 25, 2011 I have got 1988 defender with a 300tdi + lt77 + original T/box top speed 40mph. I would've expected to get 50ish. If I change T/box to a disco T/box will this give me a better top speed. I'd like 60mph. Engine is fine, gearbox/T.box fine Just don't understand speed restricted to 40mph engine is over revving. Any ideas why speed issues. what was the original engine ? as said you might have the 1.667 ratio TB. Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted December 25, 2011 Share Posted December 25, 2011 Looks like it may be what was a petrol 110, i think that 'would' have a 1.6 transfer box wouldn;t it.......... i'd go mad if my truck went that slow! Quote Link to comment Share on other sites More sharing options...
Jim1 Posted December 25, 2011 Author Share Posted December 25, 2011 It was a 2.5 petrol. Have checked high and low ratios but high still only does 40mph. I have now got a T/Box off a MPI Disco will fit and see what happens. Quote Link to comment Share on other sites More sharing options...
Jack Sugden Posted December 28, 2011 Share Posted December 28, 2011 I fitted a 1:22 Disco transfer box out of a 300tdi into my 1987 200tdi conversion 90 with LT77, as the standard 1:4 defender box was making the 200tdi engine rev its tits off with a top speed of around 40 - 50 mph. The 1:2 box sorted it straight out. The engine revs to road speed is perfect now. The 200 and 300tdi's are higher revving engines than the N/A and turbo diesel thats why they were fitted with a different gear ratio in the transfer case to compensate for the difference in engine revs. Not sure if the 2.5 petrol has a 1:4 but a standard 90 box was a 1:4 ratio as far as I was aware. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted December 28, 2011 Share Posted December 28, 2011 I fitted a 1:22 Disco transfer box out of a 300tdi into my 1987 200tdi conversion 90 with LT77, as the standard 1:4 defender box was making the 200tdi engine rev its tits off with a top speed of around 40 - 50 mph. The 1:2 box sorted it straight out. The engine revs to road speed is perfect now. The 200 and 300tdi's are higher revving engines than the N/A and turbo diesel thats why they were fitted with a different gear ratio in the transfer case to compensate for the difference in engine revs. Not sure if the 2.5 petrol has a 1:4 but a standard 90 box was a 1:4 ratio as far as I was aware. The 1.6 box was there for the lack of power, not lack of RPM. Sounds like your on little tyres to me. Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted December 28, 2011 Share Posted December 28, 2011 The 1.4 transfer box and the tdi are a good combination with the correct diffs and the correct wheel size. If your top end is only 40 - 50 mph then you are either running silly little tyres or you're running series diffs. Put the right sized tyres on it, make sure you have the correct diffs and you will enjoy driving your Land Rover right up to and beyond motorway speeds. HTH Mo Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 28, 2011 Share Posted December 28, 2011 The 1.4 transfer box and the tdi are a good combination with the correct diffs and the correct wheel size. If your top end is only 40 - 50 mph then you are either running silly little tyres or you're running series diffs. Put the right sized tyres on it, make sure you have the correct diffs and you will enjoy driving your Land Rover right up to and beyond motorway speeds. HTH Mo Well I've got a 1.4 behind the 200tdi, and 255/85 and it doesn't like going much faster than 50 as its screaming its nuts off... Quote Link to comment Share on other sites More sharing options...
western Posted December 28, 2011 Share Posted December 28, 2011 my 110 runs 255/85 tyres & a 1.410 transfer box, it will easily pull 70 on motorway, but happier at 60/65 when the OD is engaged. Quote Link to comment Share on other sites More sharing options...
TSD Posted December 28, 2011 Share Posted December 28, 2011 Well I've got a 1.4 behind the 200tdi, and 255/85 and it doesn't like going much faster than 50 as its screaming its nuts off... The noise you are hearing is your 200tdi politely asking you to change up into fourth. Quote Link to comment Share on other sites More sharing options...
pat_pending Posted December 28, 2011 Share Posted December 28, 2011 Ever considered the clutch might be slipping? Has it always only done 40mph? Quote Link to comment Share on other sites More sharing options...
simonr Posted December 28, 2011 Share Posted December 28, 2011 40mph is way too slow! I had a 300Tdi in a 110 with a 1.4 transfer and it (could) reach 85 but would cruise at 70 all day. That was running 750x16 tyres. I later swapped the 300 for a 200 and although it was a bit slower (80 ish) it still went pretty well. I ran it for a weekend with 205 tyres - and it went even faster! Even though you say the engine and box are fine - the numbers say different! Either that or you are mis-reading when the engine is over-revving. Si Quote Link to comment Share on other sites More sharing options...
eds Posted December 28, 2011 Share Posted December 28, 2011 Am I reading something into this - " Have checked high and low ratios but high still only does 40mph" High still does only 40mph I would have said, I get 40 in high and 20 in low Maybe you are still in low? Sounds like low! I think 5th in low is same as 3 in high roughly..............I easily get 75mph with 200tdi lt77 1.4 ratio Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 28, 2011 Share Posted December 28, 2011 The noise you are hearing is your 200tdi politely asking you to change up into fourth. Thats in 5th! Quote Link to comment Share on other sites More sharing options...
TSD Posted December 28, 2011 Share Posted December 28, 2011 Thats in 5th! Well if your truck is as described, "1.4 behind the 200tdi, and 255/85" and assuming standard LT77, 3.54 diffs and 16" wheels, then I calculate the rev limiter is approx. 50mph in 3rd. The numbers might be a bit out, depending on gear ratios and 'real world' tyre size, but if you took the tyres off and ran on the rims, you'd get still 47mph in 5th! My 200tdi 90 LT77, 1.41 LT230, 3.54diffs and 265/75R16 will hit easily exceed 80mph on the GPS. Fuelling isn't standard, and the EGTs are scary flat out, but that doesn't change the revs. Either there's something wrong with your truck or your ears Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted December 28, 2011 Share Posted December 28, 2011 Well I've got a 1.4 behind the 200tdi, and 255/85 and it doesn't like going much faster than 50 as its screaming its nuts off... Then you have a problem, Ross. Something is not right with your 90's drivetrain or your speedo is knackered. Best get out there ... Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted December 28, 2011 Share Posted December 28, 2011 Yeah that's not right. I have the same drivetrain as you Ross, with even smaller tyres, and mine only really starts screaming at 70ish. Will cruise at 60mph all day long. Then again it depends on one's idea of 'screaming'. I have quite a bit of soundproofing, so that may help things sound quieter. Definitely not topping out though, it will pull all the way to 80ish before it runs out of puff. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 28, 2011 Share Posted December 28, 2011 Well if your truck is as described, "1.4 behind the 200tdi, and 255/85" and assuming standard LT77, 3.54 diffs and 16" wheels, then I calculate the rev limiter is approx. 50mph in 3rd. The numbers might be a bit out, depending on gear ratios and 'real world' tyre size, but if you took the tyres off and ran on the rims, you'd get still 47mph in 5th! My 200tdi 90 LT77, 1.41 LT230, 3.54diffs and 265/75R16 will hit easily exceed 80mph on the GPS. Fuelling isn't standard, and the EGTs are scary flat out, but that doesn't change the revs. Either there's something wrong with your truck or your ears Thats all correct... but I'm not saying its on the limiter at 50 . I've had 65 out of it, but the valves might as well have been banging off the bonnet! Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 28, 2011 Share Posted December 28, 2011 Thats all correct... but I'm not saying its on the limiter at 50 . I've had 65 out of it, but the valves might as well have been banging off the bonnet! Fair point on the insulation James... maybe its the fact I can hear mine?!! Quote Link to comment Share on other sites More sharing options...
Jim1 Posted December 28, 2011 Author Share Posted December 28, 2011 I'm now on 235/85x16 tyres, Diffs are original don't know the ratios, Never thought about changing them?. everything is original accept the 300tdi. the petrol lump only managed 60mph at a push. will be looking at it tomorrow if it don't improve will fit the MPI T/Box No insulation floors not bolted down yet so get loads of noise but thats expected. Quote Link to comment Share on other sites More sharing options...
pat_pending Posted December 28, 2011 Share Posted December 28, 2011 I'm now on 235/85x16 tyres, Diffs are original don't know the ratios, Never thought about changing them?. everything is original accept the 300tdi. the petrol lump only managed 60mph at a push. will be looking at it tomorrow if it don't improve will fit the MPI T/Box No insulation floors not bolted down yet so get loads of noise but thats expected. So it's only been this slow since the 300tdi went in? Again, could the clutch be slipping? Does it get full throttle at the injection pump? Quote Link to comment Share on other sites More sharing options...
Jim1 Posted December 28, 2011 Author Share Posted December 28, 2011 No clutch not slipping, yes full throttle now went through 2 brand new lift pumps before getting full revs. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.