Cutting Through The Cr*p Cake: The Renault Gearbox - how strong is it?

[Vanya]

Hey guys,

Figured I'd create a little thread to get this cleared up once and for all (feel free to send me hate-mail if there's already a billion and one discussions about this...I just want a clear and concise answer)

So, I went and bought an Esprit half a year back, despite all the ominous warnings from the interwebz, german-car fans and other car knowledgables, most of whom have actually ever owned a Lotus, much less an Esprit, basing their know-how on hearsay.

Thus far, I have found out that about 90% of the bad stuff I've heard about the Esprit seems to be complete bollocks ranging from "poor visibility", "terrifying to drive around town", "extremely expensive parts" and a myriad other, more technical matters. As a first-time buyer, I was totally out of my element going to see the car and was focusing on probably all the wrong things despite earlier research - things such as "has the ABS-pressure switch been acting up" and "Is the gearbox 1st/2nd totally fried?" - of course there are many more, equally imporant, things to look out for when buying an Esprit, and if I had to evaluate one today, pre-purchase, I'd see it in a whole different light.

However one "concern" remains - the gearbox. How gentle do I REALLY have to be with it?

I'm not a redline driver, I don't use it for quarter-mile races, but I do genuinely like its accelaration in 2nd gear!

Unfortunately, my earlier brainwashing by fear-mongers has resulted in a bit of worry over how I should treat the car - I've heard that 1st and 2nd are VERY sensitive and fragile and should NEVER be used for hard accelerations, whereas at the same time, people who RACE their SE's (or four-pots in general) have said they have never experienced any issues and that it's all bullcrap.

Now my car happens to be a four-pot SE running stock, so I shouldn't have a V8 owner's kind of concerns...

What do you guys and gals say, how much truth is there to the above? Do I have to drive like a granny before I hit a decent speed in 3rd and above, or should I lay these fears to rest once and for all?

Muchas gracias in advance!

Regards,

Vanya S.

[Bibs]

Very few people with standard cars have had issues with their gearboxes and if anything it's 5th gear which is the weak link, but only in high RPM situations where the throttle is dropped then rapidly re-applied. That said, there are only a handful of times that's happened too!

I drove my SE in the style it was intended for, including occasional track use and it was fine

[jonwat]

I fitted the high torque chip into my '95 S4s and on a good tarmac, dry road it would spin the wheels when the turbo came on boost causing the back end to fishtail.

I even had to drive it 50 miles once without the clutch after the fork broke & I never had any problems, having said that although I did give it some welly on many occasions I never abused it.

I always think forums are great for help & problem solving but it's way too easy to get worried after reading the occasional horror story probably by someone with no mechanical sympathy who's abused the vehicle, ignoring any strange noises etc.

Just make sure she's serviced regularly by a good mechanic & drive & enjoy her

[Vanya]

Will do! Thanks for the advice!

[lotus-62]

in the gt40 replica club they use the un1-13 (from an renault 21 turbo) they match it to 5 liters of ford v8 (350-380bhp) only the 5th gear gives a problem but there are stronger 5th gears around. other problem with the 5th gear is it's design, it hangs on the end of the box with only 1 bearing......... so yes you need to be gentle in 5. the diff does not like wheel spinning a lot and some are running oil coolers on the box if you want to learn a lot about the un1 box go to www.gt40s.com , go to the gearbox section and search for renault un1, have fun reading...

[DanR]

There can be problems with 1st and 2nd gear syncros. Especially if the next gear is selected too rapidly. Power is transmitted through 18 dog teeth which can snap off with savage gear changing. So be aware of this and make sure the translator adjustments are always spot on. If not the syncro problem becomes exacerbated.

[rogerch]

Refraining from "Quick" gear changing before the gearbox has reached operating temperature is strongly recommended.

[Vanya]

Great advice guys, keep it coming

[PhillipM]

Hey all, newbie here, but I have to agree with the above, there's no real strength issues with anything bar 5th - and that's down to the design of the shaft and the gear being hung outside the casing, rather than an issue with the gearpair itself.
 As mentioned, the differential's don't take kindly to one wheel spinning for too long - in fact the only time I've damaged a diff* so far is when it was spinning one wheel a lot faster than the other for a good 30 seconds of full throttle - I think the oil overheats given the spur gears just run on a backing pad, and then you get galling and a tooth lets go. The preload on the crown and pinion is vital too.
  Input shafts can be a little weak but tend to just wear the splines rather than outright snap unless you have silly amounts of load.

Syncro's are relatively old design and fairly fragile - if you baby them until the oil is warm, they are fine. The other option is use an oil such as Total BV75w-80 which massively improves things but possibly at the expense of wear on the hypoid diff gears - although it hasn't been an issue for us so far.

The box will quite happily take 10,000rpm's of input speed from what I've found, but the nose bearing on the input shaft is worth replacing beforehand!

 

*Albiet using the UN5 diff with it's 4-spider internals rather than the 2 spider.

[PhillipM]

^I'm still trying to find a plate-style diff for that though if anyone has any ideas....

[Vulcan Grey]

The 1991 Esprit X180-R had a ZF plate type LSD.

 

Looks like GTO Racing sells a ZF clutch type for the UN1

[Günter]

 

..one twinplate-set of two worn sets of plates (AP-racing , twinplate type ..no torsional damping, organic layer ..used for "some trackdays" and a lot of city-runs with stop & go and clutch engage on both of the sets)

 

 

..my input-shaft (V8 , as you see by the twin wear marks) , after around 97.000km

 

 

..same input-shaft, after some 'McGyver style diy-works'  (overlay-welding, even knowing that this way is not the usual in mechanical view..!) ..and one week of 'handcrafting' with angle grinder and micro file for all the splines

 

So far 3 trackdays this year, and weekly town rides ..a bit rough on engage (as the surface is not perfect and the material structure does now wear different -but still going strong so far)

 

 

 

 

[DanR]

If you measure it, the shear area of the splines on the two v8 clutch plates is less than that on the 4 cylinder single plate clutch. No wonder they chew themselves out.