Gearbox options for 3500S

R

robin collis

Active Member
I have an early 3500S, 1971, and while (touch wood) the gearbox is OK it is not perfect and has been rebuilt once. One of my dreams is to convert the car to a 5 speed 'box.
Could the Forum comment on the options that I have to do this
I see my options as:-
1. Stick to the original 4 speed box and rebuild if it fails again. Easiest option so long a parts are available to rebuild the 'box How many times can I do this?

2. Convert to 5 speed 'box using SD1 'box and parts. Could be the easiest conversion to do as parts available, but SD1 boxes are getting hard to find in good condition.

3. Convert with another Rover 5 speed box. I believe that such 'boxes are available from land-rover and Leyland Daf vans, but I am not familiar with the different types of 'box available and I do not want to end up with ratios o suit a land rover or Van. Could someone with the knowledge give information a to which of these 'boxes might be suitable and possible to find.

4 Convert to another make of speed 'box I think that I have heard that Toyota 5 speed saloon car 'boxes can be used and that someone makes bell-housing to fit these to the Rover V8 Has anyone on the Forum done this conversion, or know who has done it? Any advice as to what type of Toyota 'box is suitable? oul a Celica 'box take the torque and power of a V8?

What other makes of gearbox could be used, or more important, have been used?
I do not have workshop facilities so would have to get the conversion done by a specialist, and I really want to use a tried and tested conversion and not be a pioneer with the conversion.
I cannot believe that I am the only P6 owner ho is thinking of gearbox conversion, so it would be great to get all the information in one place so that we can make plans,

Thanks in advance.
 
Hi, The Only problem with keep rebuilding the 'S' 4 speed 'box is parts supply in particular the rear mainshaft bearing, the replacements weren't dimensionally accurate. Unless anyone else knows different.

The LT77 had various minor ratio differences but you won't notice it behind the V8, the Van 'boxes will work but forget the LR 'boxes they have different length and style of first motion and mainshaft so would have to be replaced, more expense.

I can't comment on the Toyota items, they are well regarded but are more popular and plentiful down under.

As you will need the work to be done by someone else you would be advised to keep it simple otherwise it could run away with the cost.

I'm sure others will be along with other opinions or choices.

Good luck.

Colin
 
Having recently just converted my 3500s to a 5 speed box, it was easy enough to get the parts i needed. It took a couple of months, but i found everything.
I did the conversion in my garage at home. It's a standard size garage of 8ft x 16ft. I have no power either.
The only help i required was to lift the old box out and lift the new box it. The rest i did myself even though i have never done this before. I asked plenty of questions on here and tackled it. 5 speed conversion really is one of the best upgrades to do.
Where abouts in the UK are you?
 
ampwhu said:
Having recently just converted my 3500s to a 5 speed box, it was easy enough to get the parts i needed. It took a couple of months, but i found everything.
I did the conversion in my garage at home. It's a standard size garage of 8ft x 16ft. I have no power either.
The only help i required was to lift the old box out and lift the new box it. The rest i did myself even though i have never done this before. I asked plenty of questions on here and tackled it. 5 speed conversion really is one of the best upgrades to do.
Where abouts in the UK are you?
Click to expand...

Woking Surrey
 
I originally had the same 4 speed and converted to a 5 speed something like 7 years ago - was fairly straightforward as I remember but I think your biggest problem will be finding a good condition 2WD LT77 nowadays.
The LT77 although better has it's faults (like baulking gearchanges when cold), if I was doing this again on a standard tune 3.5 V8 I'd seriously consider asking Vitesse if they can do a Mazda p6 kit.
 
Have recently put an LT77 in my 3500S - see my project thread for details and pics - effort required is not trivial, but reward is well worth it - cruising is much nicer. I got a complete TR7 box (with bellhousing) from a triumph parts place. Several posters here have done this, each with their own version of the rear mount. Separately I picked up another LT77 (25A...C) without a bellhousing, unknown origin - selection issues, a problem with rear layshaft bearing. The one in the car (19A.....A) now has some selection issues, and maybe a little noisy in the low gears, so I decided to get this spare box overhauled - easier said than done down here. In the end I found a workshop that specialized in MGs, and they offered to do it if I could supply documentation. Claiming their man was the best in the business, cost me A$2500. Apparently the C suffix boxes are better and stronger, and parts not impossible to find. The 25A prefix does not appear in any documents I have found. Its 5th gear is a 0.833 ratio - ie +20%.
My suggestions - if looking at LT77 go for at least a suffix C , an R380 would be better (synchro reverse, stronger, more parts available) from a TVR etc, but rare. If you can readily get a box that Dellow makes a bellhousing for our V8, factor in its cost and shipping, unless you can find a Dellow agent in UK. They do adaptors for W55, T5, R154, as well as a few autos. Re using a 5speed Mazda box (MX5) I have one in a Clubbie (lotus 7 clone) delivering 215HP to the rear wheels from a 1.8L MX5 engine with a turbo - no problems in 10k kms, although it is a bit lighter than a P6B at < 800kgs.
 

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ratwing said:
I originally had the same 4 speed and converted to a 5 speed something like 7 years ago - was fairly straightforward as I remember but I think your biggest problem will be finding a good condition 2WD LT77 nowadays.
The LT77 although better has it's faults (like baulking gearchanges when cold), if I was doing this again on a standard tune 3.5 V8 I'd seriously consider asking Vitesse if they can do a Mazda p6 kit.
Click to expand...
I met Alec Poole, racer, at a club talk and he suggested borrowing my P6 in order to develop a P6 kit, it never came to fruition, but I think it is something they would consider. Alec is associated with Vitesse.
I seem to remember measuring up one of their boxes at the NEC and the shifter position was there, or therabouts.
 
Thank you for all the replies. It seems to me that the easiest route is with a LT77. if I can find one. If not I will have to start saving to afford a Madza conversion.
Could be the preferred way, as LT77 are getting so rare. If I do the conversion, I want it to be 'once and for ever' job, so that means using good gearbox and not some dubious second -hand item that will fail. I do not have the facilities or expertise to do the conversion my self, so would have to be done by an expert, who has done it before.
 
While you look for a good LT77 I suggest you also explore the availability of a T56 box - more common these days, used in many modern cars - GM and Ford manuals use them a lot. Find out the depth of a Dellow bell housing, and then the gear lever location on a box.
This may help
Manual Transmission Dimensions
For reference, an LT77, front face (without bellhousing) to gear lever is 22.5"
 
Maybe....doubt the 24mm figure face to gear lever is correct. See above - 22.5", 57.5cm.
 
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FWIW I contacted them for some dimensions but they weren't that helpful, Vitesse on the other hand were. I wonder if the RPi kit comes from Vitesse, they look similar?
 
Using MTF94 instead of of Dexron helps massively with the cold changes on the lt77. You can get it fairly cheaply from Smith and Allan. I use it in my landrover and the P6.

As said, don't be tempted by LR boxes, they have enough differences to make things impossible. I know, as when I did my P6 conversion I had a few LR boxes laying about, and when it became clear my 2wd box had an issue I cracked them open to scavenge parts. Alas, shaft diameters, lengths etc are different so next to nothing was interchangeable.

I do have my old 4 speed box if that's any help to you? I took it out as it started rumbling, I am in Hook in Hampshire (RG27).
 
Something else to add to the mix. The LT77 box in various guises used 3 different length throwout pivot bolts - we need the middle one , and 2 different lengths of throwout bearing carriers - we need the long one. See my thread P6B S Project Car
I also used a 5/8" bore clutch master cylinder to ensure the load was acceptable, having encountered a VERY heavy clutch the first time I did the conversion. I have Redline MTF in my current LT77, seems Ok, but early days.
 
If the Mazda 5 speed fits, does the six speed fit as well? They are also fitted to Toyota Attenzas/Lexus IS 250s. Or the six speed Getrag boxes fitted to Mercedes Benz C-Class diesels/BMW 3 series diesels? There are a lot of those around.
 
Here is some more info on the MX5 boxes
miata-source.com

5-Speed vs 6-Speed NA/NB Miata Transmission

Do I need a 6-speed? How much power can a 5-speed hold? I want a 6-speed because of the overdrive. One of the more common questions/concerns we have had during our used parts sales. Here we are going to lay out the details of a 6-speed NB transmission the pros/cons of the transmission and what...
miata-source.com miata-source.com
 
jp928 said:
Here is some more info on the MX5 boxes
miata-source.com

5-Speed vs 6-Speed NA/NB Miata Transmission

Do I need a 6-speed? How much power can a 5-speed hold? I want a 6-speed because of the overdrive. One of the more common questions/concerns we have had during our used parts sales. Here we are going to lay out the details of a 6-speed NB transmission the pros/cons of the transmission and what...
miata-source.com miata-source.com
Click to expand...
That certainly makes the six speed seem a better choice. The same installation but a stronger box with the extra ratio as well.
 
I can vouch for the 5speed being robust....I am putting 215rwhp through one.
epg1GIL.jpg
 
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