Engine and Transmission Tech

Which is the better choice for my TR7 v8 conversion? We are using one of Jim's old 215 blocks, going with fuel injection and crank trigger with megasquirt. It is probably more important to me at this point for the car to be a good highway cruiser, but keep in mind the highways I drive on in WV are somewhat curvy and hilly. I have the LT77 already in the TR7, so that is a plus. Why would I want to switch to a T5? Can some of you shed some light for me?

Thanks,

Dan B

Dan-Here is the deal with the LT77 Rover 5-Speed. When it comes out of the 4 cylinder and is installed onto a Rover V8 you are going to gamble unless you get it rebuilt. 90ftlbs of torque all of a sudden to 200ftlbs of torque can also make the synchros notchy if not fail all together. I have had this happen in 2 TR8s I used a smooth tranny from a TR7. The pump inside has been know to just fail beciase it is made of some fiber material that with age falls apart. To get a LT77 rebuilt is atleast $900.00. You have a choice of two 5th gears :79 & .83 the taller gear is from 1981 TR8s & Rover SD1s onward. Another factor is if you use a 3.90 TR7 rear first gear is a joke.! It lasts about 5 feet. The 3.45 TR7 rear is best for highway and back roads. The 3.08 TR8 is great for highway but hurts acceloration. The only thing nice about the LT77 is you only need a V8 bell housing, dust shield, flywheel, corss member, pivot bolt and collar for the throw out bearing. The TR7 clutch arm, slave cylinder, clutch hose, and throw out bearing can be reused. The transmission cross member can also be reused from the TR7 but you will have to redrill the holes in the floor. You will have to also shorten the drive shaft and becareful the shifter does not hit the back of the hole in the tunnel.

The T5 is available in two horsepower/torque rating and lots of gear ratios to suite any rear axle ratio. The horsepower rating are 2 or 3 times more than a LT77. They are so many available. You will need a flywheel, clutch, bellhousing, hydraulic collar type throwout bearing, clutch hose, speedo cable adaptor or new speedo, drive shaft for the T5 and shorter, and fabricated cross memeber.

I am a pro Rover LT77 guy BUT if I was starting from scratch and wanted depndable and better gear choices I would be leaning more towards the T5 and you will never break it unlike the LT77 which I have had then self distruct!

Thanks Mike. Do you know if there is anything to do to the LT77 (ie rebuild the oil pump) that will make it less likely to crash once v8 power is applied? I don't intend to put a lot of stress on it all the time. I believe I have the 3.45 rear end, The TR7 is a 1980 model. The LT77 shifts fine even in the cold and it has about 68000 miles on it.
It would save me quite a bit of money now to keep it, but I don't want to pay more later, if you know what I mean.

LT77s I suppose they are old hat these days, but, for me they have been a reliable box, never broke one, just had to adjust the endfloat on the taper bearings, and use the right oil, it changes accordingto different books I have read,
Did you get the MGRV8, as this had the upgraded R380,

You can replace the synchros and the oil pump and look over the bearings as an over haul but you can take a gamble which at 68k miles should be resonable to say if you switch to the GM fluid you should have a good box to start with. Typically checking the input shaft and checking for play tells you what shape the bearings are in. If you have a post October/November 1979 TR7 then you have the 3.45 rear axle and with the 5 speed its is a nice all around set up.



Edited 1 time(s). Last edit at 03/10/2010 07:56PM by WedgeWorks1.

I am using a tr7 gearbox in my Morris. I bought it used with unknown mileage, had a look inside and replaced the oil pump (it was in pieces). It has been trouble free even if it is an early box. I have fitted a narrowed TR7 axle with 3,08:1 ratio. The car weighs about 1000 kg which is more or less the same as TR7. If you already have the box and can get the correct bellhousing I would choose that option. I have considered the T5 option as well as Supra box but so far have not had reliability issues. If/when there will be I may choose a stronger box. Fingers crossed...